通过 Amazon SDK 开始使用 DynamoDB 表、项目和查询

// This example application performs the following basic Amazon DynamoDB
// functions:
//
//     CreateTableAsync
//     PutItemAsync
//     UpdateItemAsync
//     BatchWriteItemAsync
//     GetItemAsync
//     DeleteItemAsync
//     Query
//     Scan
//     DeleteItemAsync
//
// The code in this example uses the AWS SDK for .NET version 3.7 and .NET 5.
// Before you run this example, download 'movies.json' from
// https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/resources/sample_files,
// and put it in the same folder as the example.
namespace DynamoDB_Basics_Scenario
{
    public class DynamoDB_Basics
    {
        // Separator for the console display.
        private static readonly string SepBar = new string('-', 80);

        public static async Task Main()
        {
            var client = new AmazonDynamoDBClient();

            var tableName = "movie_table";

            // relative path to moviedata.json in the local repository.
            var movieFileName = @"..\..\..\..\..\..\..\..\resources\sample_files\movies.json";

            DisplayInstructions();

            // Create a new table and wait for it to be active.
            Console.WriteLine($"Creating the new table: {tableName}");

            var success = await DynamoDbMethods.CreateMovieTableAsync(client, tableName);

            if (success)
            {
                Console.WriteLine($"\nTable: {tableName} successfully created.");
            }
            else
            {
                Console.WriteLine($"\nCould not create {tableName}.");
            }

            WaitForEnter();

            // Add a single new movie to the table.
            var newMovie = new Movie
            {
                Year = 2021,
                Title = "Spider-Man: No Way Home",
            };

            success = await DynamoDbMethods.PutItemAsync(client, newMovie, tableName);
            if (success)
            {
                Console.WriteLine($"Added {newMovie.Title} to the table.");
            }
            else
            {
                Console.WriteLine("Could not add movie to table.");
            }

            WaitForEnter();

            // Update the new movie by adding a plot and rank.
            var newInfo = new MovieInfo
            {
                Plot = "With Spider-Man's identity now revealed, Peter asks" +
                "Doctor Strange for help. When a spell goes wrong, dangerous" +
                "foes from other worlds start to appear, forcing Peter to" +
                "discover what it truly means to be Spider-Man.",
                Rank = 9,
            };

            success = await DynamoDbMethods.UpdateItemAsync(client, newMovie, newInfo, tableName);
            if (success)
            {
                Console.WriteLine($"Successfully updated the movie: {newMovie.Title}");
            }
            else
            {
                Console.WriteLine("Could not update the movie.");
            }

            WaitForEnter();

            // Add a batch of movies to the DynamoDB table from a list of
            // movies in a JSON file.
            var itemCount = await DynamoDbMethods.BatchWriteItemsAsync(client, movieFileName);
            Console.WriteLine($"Added {itemCount} movies to the table.");

            WaitForEnter();

            // Get a movie by key. (partition + sort)
            var lookupMovie = new Movie
            {
                Title = "Jurassic Park",
                Year = 1993,
            };

            Console.WriteLine("Looking for the movie \"Jurassic Park\".");
            var item = await DynamoDbMethods.GetItemAsync(client, lookupMovie, tableName);
            if (item.Count > 0)
            {
                DynamoDbMethods.DisplayItem(item);
            }
            else
            {
                Console.WriteLine($"Couldn't find {lookupMovie.Title}");
            }

            WaitForEnter();

            // Delete a movie.
            var movieToDelete = new Movie
            {
                Title = "The Town",
                Year = 2010,
            };

            success = await DynamoDbMethods.DeleteItemAsync(client, tableName, movieToDelete);

            if (success)
            {
                Console.WriteLine($"Successfully deleted {movieToDelete.Title}.");
            }
            else
            {
                Console.WriteLine($"Could not delete {movieToDelete.Title}.");
            }

            WaitForEnter();

            // Use Query to find all the movies released in 2010.
            int findYear = 2010;
            Console.WriteLine($"Movies released in {findYear}");
            var queryCount = await DynamoDbMethods.QueryMoviesAsync(client, tableName, findYear);
            Console.WriteLine($"Found {queryCount} movies released in {findYear}");

            WaitForEnter();

            // Use Scan to get a list of movies from 2001 to 2011.
            int startYear = 2001;
            int endYear = 2011;
            var scanCount = await DynamoDbMethods.ScanTableAsync(client, tableName, startYear, endYear);
            Console.WriteLine($"Found {scanCount} movies released between {startYear} and {endYear}");

            WaitForEnter();

            // Delete the table.
            success = await DynamoDbMethods.DeleteTableAsync(client, tableName);

            if (success)
            {
                Console.WriteLine($"Successfully deleted {tableName}");
            }
            else
            {
                Console.WriteLine($"Could not delete {tableName}");
            }

            Console.WriteLine("The DynamoDB Basics example application is done.");

            WaitForEnter();
        }

        /// <summary>
        /// Displays the description of the application on the console.
        /// </summary>
        private static void DisplayInstructions()
        {
            Console.Clear();
            Console.WriteLine();
            Console.Write(new string(' ', 28));
            Console.WriteLine("DynamoDB Basics Example");
            Console.WriteLine(SepBar);
            Console.WriteLine("This demo application shows the basics of using DynamoDB with the AWS SDK for");
            Console.WriteLine(".NET version 3.7 and .NET Core 5.");
            Console.WriteLine(SepBar);
            Console.WriteLine("The application does the following:");
            Console.WriteLine("\t1. Creates a table with partition: year and sort:title.");
            Console.WriteLine("\t2. Adds a single movie to the table.");
            Console.WriteLine("\t3. Adds movies to the table from moviedata.json.");
            Console.WriteLine("\t4. Updates the rating and plot of the movie that was just added.");
            Console.WriteLine("\t5. Gets a movie using its key (partition + sort).");
            Console.WriteLine("\t6. Deletes a movie.");
            Console.WriteLine("\t7. Uses QueryAsync to return all movies released in a given year.");
            Console.WriteLine("\t8. Uses ScanAsync to return all movies released within a range of years.");
            Console.WriteLine("\t9. Finally, it deletes the table that was just created.");
            WaitForEnter();
        }

        /// <summary>
        /// Simple method to wait for the Enter key to be pressed.
        /// </summary>
        private static void WaitForEnter()
        {
            Console.WriteLine("\nPress <Enter> to continue.");
            Console.WriteLine(SepBar);
            _ = Console.ReadLine();
        }
    }
}

创建一个包含影片数据的表。

        /// <summary>
        /// Creates a new Amazon DynamoDB table and then waits for the new
        /// table to become active.
        /// </summary>
        /// <param name="client">An initialized Amazon DynamoDB client object.</param>
        /// <param name="tableName">The name of the table to create.</param>
        /// <returns>A Boolean value indicating the success of the operation.</returns>
        public static async Task<bool> CreateMovieTableAsync(AmazonDynamoDBClient client, string tableName)
        {
            var response = await client.CreateTableAsync(new CreateTableRequest
            {
                TableName = tableName,
                AttributeDefinitions = new List<AttributeDefinition>()
                {
                    new AttributeDefinition
                    {
                        AttributeName = "title",
                        AttributeType = "S",
                    },
                    new AttributeDefinition
                    {
                        AttributeName = "year",
                        AttributeType = "N",
                    },
                },
                KeySchema = new List<KeySchemaElement>()
                {
                    new KeySchemaElement
                    {
                        AttributeName = "year",
                        KeyType = "HASH",
                    },
                    new KeySchemaElement
                    {
                        AttributeName = "title",
                        KeyType = "RANGE",
                    },
                },
                ProvisionedThroughput = new ProvisionedThroughput
                {
                    ReadCapacityUnits = 5,
                    WriteCapacityUnits = 5,
                },
            });

            // Wait until the table is ACTIVE and then report success.
            Console.Write("Waiting for table to become active...");

            var request = new DescribeTableRequest
            {
                TableName = response.TableDescription.TableName,
            };

            TableStatus status;

            int sleepDuration = 2000;

            do
            {
                System.Threading.Thread.Sleep(sleepDuration);

                var describeTableResponse = await client.DescribeTableAsync(request);
                status = describeTableResponse.Table.TableStatus;

                Console.Write(".");
            }
            while (status != "ACTIVE");

            return status == TableStatus.ACTIVE;
        }

将单个影片添加到表中。

        /// <summary>
        /// Adds a new item to the table.
        /// </summary>
        /// <param name="client">An initialized Amazon DynamoDB client object.</param>
        /// <param name="newMovie">A Movie object containing informtation for
        /// the movie to add to the table.</param>
        /// <param name="tableName">The name of the table where the item will be added.</param>
        /// <returns>A Boolean value that indicates the results of adding the item.</returns>
        public static async Task<bool> PutItemAsync(AmazonDynamoDBClient client, Movie newMovie, string tableName)
        {
            var item = new Dictionary<string, AttributeValue>
            {
                ["title"] = new AttributeValue { S = newMovie.Title },
                ["year"] = new AttributeValue { N = newMovie.Year.ToString() },
            };

            var request = new PutItemRequest
            {
                TableName = tableName,
                Item = item,
            };

            var response = await client.PutItemAsync(request);
            return response.HttpStatusCode == System.Net.HttpStatusCode.OK;
        }

更新表中的单个项目。

        /// <summary>
        /// Updates an existing item in the movies table.
        /// </summary>
        /// <param name="client">An initialized Amazon DynamoDB client object.</param>
        /// <param name="newMovie">A Movie object containing information for
        /// the movie to update.</param>
        /// <param name="newInfo">A MovieInfo object that contains the
        /// information that will be changed.</param>
        /// <param name="tableName">The name of the table that contains the movie.</param>
        /// <returns>A Boolean value that indicates the success of the operation.</returns>
        public static async Task<bool> UpdateItemAsync(
            AmazonDynamoDBClient client,
            Movie newMovie,
            MovieInfo newInfo,
            string tableName)
        {
            var key = new Dictionary<string, AttributeValue>
            {
                ["title"] = new AttributeValue { S = newMovie.Title },
                ["year"] = new AttributeValue { N = newMovie.Year.ToString() },
            };
            var updates = new Dictionary<string, AttributeValueUpdate>
            {
                ["info.plot"] = new AttributeValueUpdate
                {
                    Action = AttributeAction.PUT,
                    Value = new AttributeValue { S = newInfo.Plot },
                },

                ["info.rating"] = new AttributeValueUpdate
                {
                    Action = AttributeAction.PUT,
                    Value = new AttributeValue { N = newInfo.Rank.ToString() },
                },
            };

            var request = new UpdateItemRequest
            {
                AttributeUpdates = updates,
                Key = key,
                TableName = tableName,
            };

            var response = await client.UpdateItemAsync(request);

            return response.HttpStatusCode == System.Net.HttpStatusCode.OK;
        }

从影片表中检索单个项目。

        /// <summary>
        /// Gets information about an existing movie from the table.
        /// </summary>
        /// <param name="client">An initialized Amazon DynamoDB client object.</param>
        /// <param name="newMovie">A Movie object containing information about
        /// the movie to retrieve.</param>
        /// <param name="tableName">The name of the table containing the movie.</param>
        /// <returns>A Dictionary object containing information about the item
        /// retrieved.</returns>
        public static async Task<Dictionary<string, AttributeValue>> GetItemAsync(AmazonDynamoDBClient client, Movie newMovie, string tableName)
        {
            var key = new Dictionary<string, AttributeValue>
            {
                ["title"] = new AttributeValue { S = newMovie.Title },
                ["year"] = new AttributeValue { N = newMovie.Year.ToString() },
            };

            var request = new GetItemRequest
            {
                Key = key,
                TableName = tableName,
            };

            var response = await client.GetItemAsync(request);
            return response.Item;
        }

将一批项目写入影片表。

        /// <summary>
        /// Loads the contents of a JSON file into a list of movies to be
        /// added to the DynamoDB table.
        /// </summary>
        /// <param name="movieFileName">The full path to the JSON file.</param>
        /// <returns>A generic list of movie objects.</returns>
        public static List<Movie> ImportMovies(string movieFileName)
        {
            if (!File.Exists(movieFileName))
            {
                return null;
            }

            using var sr = new StreamReader(movieFileName);
            string json = sr.ReadToEnd();
            var allMovies = JsonConvert.DeserializeObject<List<Movie>>(json);

            // Now return the first 250 entries.
            return allMovies.GetRange(0, 250);
        }

        /// <summary>
        /// Writes 250 items to the movie table.
        /// </summary>
        /// <param name="client">The initialized DynamoDB client object.</param>
        /// <param name="movieFileName">A string containing the full path to
        /// the JSON file containing movie data.</param>
        /// <returns>A long integer value representing the number of movies
        /// imported from the JSON file.</returns>
        public static async Task<long> BatchWriteItemsAsync(
            AmazonDynamoDBClient client,
            string movieFileName)
        {
            var movies = ImportMovies(movieFileName);
            if (movies is null)
            {
                Console.WriteLine("Couldn't find the JSON file with movie data.");
                return 0;
            }

            var context = new DynamoDBContext(client);

            var bookBatch = context.CreateBatchWrite<Movie>();
            bookBatch.AddPutItems(movies);

            Console.WriteLine("Adding imported movies to the table.");
            await bookBatch.ExecuteAsync();

            return movies.Count;
        }

从表中删除单个项目。

        /// <summary>
        /// Deletes a single item from a DynamoDB table.
        /// </summary>
        /// <param name="client">The initialized DynamoDB client object.</param>
        /// <param name="tableName">The name of the table from which the item
        /// will be deleted.</param>
        /// <param name="movieToDelete">A movie object containing the title and
        /// year of the movie to delete.</param>
        /// <returns>A Boolean value indicating the success or failure of the
        /// delete operation.</returns>
        public static async Task<bool> DeleteItemAsync(
            AmazonDynamoDBClient client,
            string tableName,
            Movie movieToDelete)
        {
            var key = new Dictionary<string, AttributeValue>
            {
                ["title"] = new AttributeValue { S = movieToDelete.Title },
                ["year"] = new AttributeValue { N = movieToDelete.Year.ToString() },
            };

            var request = new DeleteItemRequest
            {
                TableName = tableName,
                Key = key,
            };

            var response = await client.DeleteItemAsync(request);
            return response.HttpStatusCode == System.Net.HttpStatusCode.OK;
        }

查询表中是否有特定年份发行的影片。

        /// <summary>
        /// Queries the table for movies released in a particular year and
        /// then displays the information for the movies returned.
        /// </summary>
        /// <param name="client">The initialized DynamoDB client object.</param>
        /// <param name="tableName">The name of the table to query.</param>
        /// <param name="year">The release year for which we want to
        /// view movies.</param>
        /// <returns>The number of movies that match the query.</returns>
        public static async Task<int> QueryMoviesAsync(AmazonDynamoDBClient client, string tableName, int year)
        {
            var movieTable = Table.LoadTable(client, tableName);
            var filter = new QueryFilter("year", QueryOperator.Equal, year);

            Console.WriteLine("\nFind movies released in: {year}:");

            var config = new QueryOperationConfig()
            {
                Limit = 10, // 10 items per page.
                Select = SelectValues.SpecificAttributes,
                AttributesToGet = new List<string>
                {
                  "title",
                  "year",
                },
                ConsistentRead = true,
                Filter = filter,
            };

            // Value used to track how many movies match the
            // supplied criteria.
            var moviesFound = 0;

            Search search = movieTable.Query(config);
            do
            {
                var movieList = await search.GetNextSetAsync();
                moviesFound += movieList.Count;

                foreach (var movie in movieList)
                {
                    DisplayDocument(movie);
                }
            }
            while (!search.IsDone);

            return moviesFound;
        }

扫描此表以查找几年内发行的影片。

        public static async Task<int> ScanTableAsync(
            AmazonDynamoDBClient client,
            string tableName,
            int startYear,
            int endYear)
        {
            var request = new ScanRequest
            {
                TableName = tableName,
                ExpressionAttributeNames = new Dictionary<string, string>
                {
                  { "#yr", "year" },
                },
                ExpressionAttributeValues = new Dictionary<string, AttributeValue>
                {
                    { ":y_a", new AttributeValue { N = startYear.ToString() } },
                    { ":y_z", new AttributeValue { N = endYear.ToString() } },
                },
                FilterExpression = "#yr between :y_a and :y_z",
                ProjectionExpression = "#yr, title, info.actors[0], info.directors, info.running_time_secs",
            };

            // Keep track of how many movies were found.
            int foundCount = 0;

            var response = new ScanResponse();
            do
            {
                response = await client.ScanAsync(request);
                foundCount += response.Items.Count;
                response.Items.ForEach(i => DisplayItem(i));
            }
            while (response.LastEvaluatedKey.Count > 1);
            return foundCount;
        }

删除影片表。

        public static async Task<bool> DeleteTableAsync(AmazonDynamoDBClient client, string tableName)
        {
            var request = new DeleteTableRequest
            {
                TableName = tableName,
            };

            var response = await client.DeleteTableAsync(request);
            if (response.HttpStatusCode == System.Net.HttpStatusCode.OK)
            {
                Console.WriteLine($"Table {response.TableDescription.TableName} successfully deleted.");
                return true;
            }
            else
            {
                Console.WriteLine("Could not delete table.");
                return false;
            }
        }

    {
        Aws::Client::ClientConfiguration clientConfig;
        //  1. Create a table with partition: year (N) and sort: title (S). (CreateTable)
        if (AwsDoc::DynamoDB::createMoviesDynamoDBTable(clientConfig)) {

            AwsDoc::DynamoDB::dynamodbGettingStartedScenario(clientConfig);

            // 9. Delete the table. (DeleteTable)
            AwsDoc::DynamoDB::deleteMoviesDynamoDBTable(clientConfig);
        }
    }

//! Scenario to modify and query a DynamoDB table.
/*!
  \sa dynamodbGettingStartedScenario()
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
 */
bool AwsDoc::DynamoDB::dynamodbGettingStartedScenario(
        const Aws::Client::ClientConfiguration &clientConfiguration) {
    std::cout << std::setfill('*') << std::setw(ASTERISK_FILL_WIDTH) << " "
              << std::endl;
    std::cout << "Welcome to the Amazon DynamoDB getting started demo." << std::endl;
    std::cout << std::setfill('*') << std::setw(ASTERISK_FILL_WIDTH) << " "
              << std::endl;

    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    // 2. Add a new movie.
    Aws::String title;
    float rating;
    int year;
    Aws::String plot;
    {
        title = askQuestion(
                "Enter the title of a movie you want to add to the table: ");
        year = askQuestionForInt("What year was it released? ");
        rating = askQuestionForFloatRange("On a scale of 1 - 10, how do you rate it? ",
                                          1, 10);
        plot = askQuestion("Summarize the plot for me: ");

        Aws::DynamoDB::Model::PutItemRequest putItemRequest;
        putItemRequest.SetTableName(MOVIE_TABLE_NAME);

        putItemRequest.AddItem(YEAR_KEY,
                               Aws::DynamoDB::Model::AttributeValue().SetN(year));
        putItemRequest.AddItem(TITLE_KEY,
                               Aws::DynamoDB::Model::AttributeValue().SetS(title));

        // Create attribute for the info map.
        Aws::DynamoDB::Model::AttributeValue infoMapAttribute;

        std::shared_ptr<Aws::DynamoDB::Model::AttributeValue> ratingAttribute = Aws::MakeShared<Aws::DynamoDB::Model::AttributeValue>(
                ALLOCATION_TAG.c_str());
        ratingAttribute->SetN(rating);
        infoMapAttribute.AddMEntry(RATING_KEY, ratingAttribute);

        std::shared_ptr<Aws::DynamoDB::Model::AttributeValue> plotAttribute = Aws::MakeShared<Aws::DynamoDB::Model::AttributeValue>(
                ALLOCATION_TAG.c_str());
        plotAttribute->SetS(plot);
        infoMapAttribute.AddMEntry(PLOT_KEY, plotAttribute);

        putItemRequest.AddItem(INFO_KEY, infoMapAttribute);

        Aws::DynamoDB::Model::PutItemOutcome outcome = dynamoClient.PutItem(
                putItemRequest);
        if (!outcome.IsSuccess()) {
            std::cerr << "Failed to add an item: " << outcome.GetError().GetMessage()
                      << std::endl;
            return false;
        }
    }

    std::cout << "\nAdded '" << title << "' to '" << MOVIE_TABLE_NAME << "'."
              << std::endl;

    // 3. Update the rating and plot of the movie by using an update expression.
    {
        rating = askQuestionForFloatRange(
                Aws::String("\nLet's update your movie.\nYou rated it  ") +
                std::to_string(rating)
                + ", what new rating would you give it? ", 1, 10);
        plot = askQuestion(Aws::String("You summarized the plot as '") + plot +
                           "'.\nWhat would you say now? ");

        Aws::DynamoDB::Model::UpdateItemRequest request;
        request.SetTableName(MOVIE_TABLE_NAME);
        request.AddKey(TITLE_KEY, Aws::DynamoDB::Model::AttributeValue().SetS(title));
        request.AddKey(YEAR_KEY, Aws::DynamoDB::Model::AttributeValue().SetN(year));
        std::stringstream expressionStream;
        expressionStream << "set " << INFO_KEY << "." << RATING_KEY << " =:r, "
                         << INFO_KEY << "." << PLOT_KEY << " =:p";
        request.SetUpdateExpression(expressionStream.str());
        request.SetExpressionAttributeValues({
                                                     {":r", Aws::DynamoDB::Model::AttributeValue().SetN(
                                                             rating)},
                                                     {":p", Aws::DynamoDB::Model::AttributeValue().SetS(
                                                             plot)}
                                             });

        request.SetReturnValues(Aws::DynamoDB::Model::ReturnValue::UPDATED_NEW);

        const Aws::DynamoDB::Model::UpdateItemOutcome &result = dynamoClient.UpdateItem(
                request);
        if (!result.IsSuccess()) {
            std::cerr << "Error updating movie " + result.GetError().GetMessage()
                      << std::endl;
            return false;
        }
    }

    std::cout << "\nUpdated '" << title << "' with new attributes:" << std::endl;

    // 4. Put 250 movies in the table from moviedata.json.
    {
        std::cout << "Adding movies from a json file to the database." << std::endl;
        const size_t MAX_SIZE_FOR_BATCH_WRITE = 25;
        const size_t MOVIES_TO_WRITE = 10 * MAX_SIZE_FOR_BATCH_WRITE;
        Aws::String jsonString = getMovieJSON();
        if (!jsonString.empty()) {
            Aws::Utils::Json::JsonValue json(jsonString);
            Aws::Utils::Array<Aws::Utils::Json::JsonView> movieJsons = json.View().AsArray();
            Aws::Vector<Aws::DynamoDB::Model::WriteRequest> writeRequests;

            // To add movies with a cross-section of years, use an appropriate increment
            // value for iterating through the database.
            size_t increment = movieJsons.GetLength() / MOVIES_TO_WRITE;
            for (size_t i = 0; i < movieJsons.GetLength(); i += increment) {
                writeRequests.push_back(Aws::DynamoDB::Model::WriteRequest());
                Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> putItems = movieJsonViewToAttributeMap(
                        movieJsons[i]);
                Aws::DynamoDB::Model::PutRequest putRequest;
                putRequest.SetItem(putItems);
                writeRequests.back().SetPutRequest(putRequest);
                if (writeRequests.size() == MAX_SIZE_FOR_BATCH_WRITE) {
                    Aws::DynamoDB::Model::BatchWriteItemRequest request;
                    request.AddRequestItems(MOVIE_TABLE_NAME, writeRequests);
                    const Aws::DynamoDB::Model::BatchWriteItemOutcome &outcome = dynamoClient.BatchWriteItem(
                            request);
                    if (!outcome.IsSuccess()) {
                        std::cerr << "Unable to batch write movie data: "
                                  << outcome.GetError().GetMessage()
                                  << std::endl;
                        writeRequests.clear();
                        break;
                    }
                    else {
                        std::cout << "Added batch of " << writeRequests.size()
                                  << " movies to the database."
                                  << std::endl;
                    }
                    writeRequests.clear();
                }
            }
        }
    }

    std::cout << std::setfill('*') << std::setw(ASTERISK_FILL_WIDTH) << " "
              << std::endl;

    // 5. Get a movie by Key (partition + sort).
    {
        Aws::String titleToGet("King Kong");
        Aws::String answer = askQuestion(Aws::String(
                "Let's move on...Would you like to get info about '" + titleToGet +
                "'? (y/n) "));
        if (answer == "y") {
            Aws::DynamoDB::Model::GetItemRequest request;
            request.SetTableName(MOVIE_TABLE_NAME);
            request.AddKey(TITLE_KEY,
                           Aws::DynamoDB::Model::AttributeValue().SetS(titleToGet));
            request.AddKey(YEAR_KEY, Aws::DynamoDB::Model::AttributeValue().SetN(1933));

            const Aws::DynamoDB::Model::GetItemOutcome &result = dynamoClient.GetItem(
                    request);
            if (!result.IsSuccess()) {
                std::cerr << "Error " << result.GetError().GetMessage();
            }
            else {
                const Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> &item = result.GetResult().GetItem();
                if (!item.empty()) {
                    std::cout << "\nHere's what I found:" << std::endl;
                    printMovieInfo(item);
                }
                else {
                    std::cout << "\nThe movie was not found in the database."
                              << std::endl;
                }
            }
        }
    }

    // 6. Use Query with a key condition expression to return all movies
    //    released in a given year.
    Aws::String doAgain = "n";
    do {
        Aws::DynamoDB::Model::QueryRequest req;

        req.SetTableName(MOVIE_TABLE_NAME);

        // "year" is a DynamoDB reserved keyword and must be replaced with an
        // expression attribute name.
        req.SetKeyConditionExpression("#dynobase_year = :valueToMatch");
        req.SetExpressionAttributeNames({{"#dynobase_year", YEAR_KEY}});

        int yearToMatch = askQuestionForIntRange(
                "\nLet's get a list of movies released in"
                " a given year. Enter a year between 1972 and 2018 ",
                1972, 2018);
        Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> attributeValues;
        attributeValues.emplace(":valueToMatch",
                                Aws::DynamoDB::Model::AttributeValue().SetN(
                                        yearToMatch));
        req.SetExpressionAttributeValues(attributeValues);

        const Aws::DynamoDB::Model::QueryOutcome &result = dynamoClient.Query(req);
        if (result.IsSuccess()) {
            const Aws::Vector<Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue>> &items = result.GetResult().GetItems();
            if (!items.empty()) {
                std::cout << "\nThere were " << items.size()
                          << " movies in the database from "
                          << yearToMatch << "." << std::endl;
                for (const auto &item: items) {
                    printMovieInfo(item);
                }
                doAgain = "n";
            }
            else {
                std::cout << "\nNo movies from " << yearToMatch
                          << " were found in the database"
                          << std::endl;
                doAgain = askQuestion(Aws::String("Try another year? (y/n) "));
            }
        }
        else {
            std::cerr << "Failed to Query items: " << result.GetError().GetMessage()
                      << std::endl;
        }

    } while (doAgain == "y");

    //  7. Use Scan to return movies released within a range of years.
    //     Show how to paginate data using ExclusiveStartKey. (Scan + FilterExpression)
    {
        int startYear = askQuestionForIntRange("\nNow let's scan a range of years "
                                               "for movies in the database. Enter a start year: ",
                                               1972, 2018);
        int endYear = askQuestionForIntRange("\nEnter an end year: ",
                                             startYear, 2018);
        Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> exclusiveStartKey;
        do {
            Aws::DynamoDB::Model::ScanRequest scanRequest;
            scanRequest.SetTableName(MOVIE_TABLE_NAME);
            scanRequest.SetFilterExpression(
                    "#dynobase_year >= :startYear AND #dynobase_year <= :endYear");
            scanRequest.SetExpressionAttributeNames({{"#dynobase_year", YEAR_KEY}});

            Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> attributeValues;
            attributeValues.emplace(":startYear",
                                    Aws::DynamoDB::Model::AttributeValue().SetN(
                                            startYear));
            attributeValues.emplace(":endYear",
                                    Aws::DynamoDB::Model::AttributeValue().SetN(
                                            endYear));
            scanRequest.SetExpressionAttributeValues(attributeValues);

            if (!exclusiveStartKey.empty()) {
                scanRequest.SetExclusiveStartKey(exclusiveStartKey);
            }

            const Aws::DynamoDB::Model::ScanOutcome &result = dynamoClient.Scan(
                    scanRequest);
            if (result.IsSuccess()) {
                const Aws::Vector<Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue>> &items = result.GetResult().GetItems();
                if (!items.empty()) {
                    std::stringstream stringStream;
                    stringStream << "\nFound " << items.size() << " movies in one scan."
                                 << " How many would you like to see? ";
                    size_t count = askQuestionForInt(stringStream.str());
                    for (size_t i = 0; i < count && i < items.size(); ++i) {
                        printMovieInfo(items[i]);
                    }
                }
                else {
                    std::cout << "\nNo movies in the database between " << startYear <<
                              " and " << endYear << "." << std::endl;
                }

                exclusiveStartKey = result.GetResult().GetLastEvaluatedKey();
                if (!exclusiveStartKey.empty()) {
                    std::cout << "Not all movies were retrieved. Scanning for more."
                              << std::endl;
                }
                else {
                    std::cout << "All movies were retrieved with this scan."
                              << std::endl;
                }
            }
            else {
                std::cerr << "Failed to Scan movies: "
                          << result.GetError().GetMessage() << std::endl;
            }
        } while (!exclusiveStartKey.empty());
    }

    // 8. Delete a movie. (DeleteItem)
    {
        std::stringstream stringStream;
        stringStream << "\nWould you like to delete the movie " << title
                     << " from the database? (y/n) ";
        Aws::String answer = askQuestion(stringStream.str());
        if (answer == "y") {
            Aws::DynamoDB::Model::DeleteItemRequest request;
            request.AddKey(YEAR_KEY, Aws::DynamoDB::Model::AttributeValue().SetN(year));
            request.AddKey(TITLE_KEY,
                           Aws::DynamoDB::Model::AttributeValue().SetS(title));
            request.SetTableName(MOVIE_TABLE_NAME);

            const Aws::DynamoDB::Model::DeleteItemOutcome &result = dynamoClient.DeleteItem(
                    request);
            if (result.IsSuccess()) {
                std::cout << "\nRemoved \"" << title << "\" from the database."
                          << std::endl;
            }
            else {
                std::cerr << "Failed to delete the movie: "
                          << result.GetError().GetMessage()
                          << std::endl;
            }
        }
    }

    return true;
}

//! Routine to convert a JsonView object to an attribute map.
/*!
  \sa movieJsonViewToAttributeMap()
  \param jsonView: Json view object.
  \return map: Map that can be used in a DynamoDB request.
 */
Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue>
AwsDoc::DynamoDB::movieJsonViewToAttributeMap(
        const Aws::Utils::Json::JsonView &jsonView) {
    Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> result;

    if (jsonView.KeyExists(YEAR_KEY)) {
        result[YEAR_KEY].SetN(jsonView.GetInteger(YEAR_KEY));
    }
    if (jsonView.KeyExists(TITLE_KEY)) {
        result[TITLE_KEY].SetS(jsonView.GetString(TITLE_KEY));
    }
    if (jsonView.KeyExists(INFO_KEY)) {
        Aws::Map<Aws::String, const std::shared_ptr<Aws::DynamoDB::Model::AttributeValue>> infoMap;
        Aws::Utils::Json::JsonView infoView = jsonView.GetObject(INFO_KEY);
        if (infoView.KeyExists(RATING_KEY)) {
            std::shared_ptr<Aws::DynamoDB::Model::AttributeValue> attributeValue = std::make_shared<Aws::DynamoDB::Model::AttributeValue>();
            attributeValue->SetN(infoView.GetDouble(RATING_KEY));
            infoMap.emplace(std::make_pair(RATING_KEY, attributeValue));
        }
        if (infoView.KeyExists(PLOT_KEY)) {
            std::shared_ptr<Aws::DynamoDB::Model::AttributeValue> attributeValue = std::make_shared<Aws::DynamoDB::Model::AttributeValue>();
            attributeValue->SetS(infoView.GetString(PLOT_KEY));
            infoMap.emplace(std::make_pair(PLOT_KEY, attributeValue));
        }

        result[INFO_KEY].SetM(infoMap);
    }

    return result;
}

//! Create a DynamoDB table to be used in sample code scenarios.
/*!
  \sa createMoviesDynamoDBTable()
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
*/
bool AwsDoc::DynamoDB::createMoviesDynamoDBTable(
        const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    bool movieTableAlreadyExisted = false;

    {
        Aws::DynamoDB::Model::CreateTableRequest request;

        Aws::DynamoDB::Model::AttributeDefinition yearAttributeDefinition;
        yearAttributeDefinition.SetAttributeName(YEAR_KEY);
        yearAttributeDefinition.SetAttributeType(
                Aws::DynamoDB::Model::ScalarAttributeType::N);
        request.AddAttributeDefinitions(yearAttributeDefinition);

        Aws::DynamoDB::Model::AttributeDefinition titleAttributeDefinition;
        yearAttributeDefinition.SetAttributeName(TITLE_KEY);
        yearAttributeDefinition.SetAttributeType(
                Aws::DynamoDB::Model::ScalarAttributeType::S);
        request.AddAttributeDefinitions(yearAttributeDefinition);

        Aws::DynamoDB::Model::KeySchemaElement yearKeySchema;
        yearKeySchema.WithAttributeName(YEAR_KEY).WithKeyType(
                Aws::DynamoDB::Model::KeyType::HASH);
        request.AddKeySchema(yearKeySchema);

        Aws::DynamoDB::Model::KeySchemaElement titleKeySchema;
        yearKeySchema.WithAttributeName(TITLE_KEY).WithKeyType(
                Aws::DynamoDB::Model::KeyType::RANGE);
        request.AddKeySchema(yearKeySchema);

        Aws::DynamoDB::Model::ProvisionedThroughput throughput;
        throughput.WithReadCapacityUnits(
                PROVISIONED_THROUGHPUT_UNITS).WithWriteCapacityUnits(
                PROVISIONED_THROUGHPUT_UNITS);
        request.SetProvisionedThroughput(throughput);
        request.SetTableName(MOVIE_TABLE_NAME);

        std::cout << "Creating table '" << MOVIE_TABLE_NAME << "'..." << std::endl;
        const Aws::DynamoDB::Model::CreateTableOutcome &result = dynamoClient.CreateTable(
                request);
        if (!result.IsSuccess()) {
            if (result.GetError().GetErrorType() ==
                Aws::DynamoDB::DynamoDBErrors::RESOURCE_IN_USE) {
                std::cout << "Table already exists." << std::endl;
                movieTableAlreadyExisted = true;
            }
            else {
                std::cerr << "Failed to create table: "
                          << result.GetError().GetMessage();
                return false;
            }
        }
    }

    // Wait for table to become active.
    if (!movieTableAlreadyExisted) {
        std::cout << "Waiting for table '" << MOVIE_TABLE_NAME
                  << "' to become active...." << std::endl;
        if (!AwsDoc::DynamoDB::waitTableActive(MOVIE_TABLE_NAME, clientConfiguration)) {
            return false;
        }
        std::cout << "Table '" << MOVIE_TABLE_NAME << "' created and active."
                  << std::endl;
    }

    return true;
}

//! Delete the DynamoDB table used for sample code scenarios.
/*!
  \sa deleteMoviesDynamoDBTable()
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
*/
bool AwsDoc::DynamoDB::deleteMoviesDynamoDBTable(
        const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    Aws::DynamoDB::Model::DeleteTableRequest request;
    request.SetTableName(MOVIE_TABLE_NAME);

    const Aws::DynamoDB::Model::DeleteTableOutcome &result = dynamoClient.DeleteTable(
            request);
    if (result.IsSuccess()) {
        std::cout << "Your table \""
                  << result.GetResult().GetTableDescription().GetTableName()
                  << " was deleted.\n";
    }
    else {
        std::cerr << "Failed to delete table: " << result.GetError().GetMessage()
                  << std::endl;
    }

    return result.IsSuccess();
}

//! Query a newly created DynamoDB table until it is active.
/*!
  \sa waitTableActive()
  \param waitTableActive: The DynamoDB table's name.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
*/
bool AwsDoc::DynamoDB::waitTableActive(const Aws::String &tableName,
                                       const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);
    // Repeatedly call DescribeTable until table is ACTIVE.
    const int MAX_QUERIES = 20;
    Aws::DynamoDB::Model::DescribeTableRequest request;
    request.SetTableName(tableName);

    int count = 0;
    while (count < MAX_QUERIES) {
        const Aws::DynamoDB::Model::DescribeTableOutcome &result = dynamoClient.DescribeTable(
                request);
        if (result.IsSuccess()) {
            Aws::DynamoDB::Model::TableStatus status = result.GetResult().GetTable().GetTableStatus();

            if (Aws::DynamoDB::Model::TableStatus::ACTIVE != status) {
                std::this_thread::sleep_for(std::chrono::seconds(1));
            }
            else {
                return true;
            }
        }
        else {
            std::cerr << "Error DynamoDB::waitTableActive "
                      << result.GetError().GetMessage() << std::endl;
            return false;
        }
        count++;
    }
    return false;
}

创建调用 DynamoDB 操作的结构和方法。

// TableBasics encapsulates the Amazon DynamoDB service actions used in the examples.
// It contains a DynamoDB service client that is used to act on the specified table.
type TableBasics struct {
	DynamoDbClient *dynamodb.Client
	TableName      string
}



// TableExists determines whether a DynamoDB table exists.
func (basics TableBasics) TableExists() (bool, error) {
	exists := true
	_, err := basics.DynamoDbClient.DescribeTable(
		context.TODO(), &dynamodb.DescribeTableInput{TableName: aws.String(basics.TableName)},
	)
	if err != nil {
		var notFoundEx *types.ResourceNotFoundException
		if errors.As(err, &notFoundEx) {
			log.Printf("Table %v does not exist.\n", basics.TableName)
			err = nil
		} else {
			log.Printf("Couldn't determine existence of table %v. Here's why: %v\n", basics.TableName, err)
		}
		exists = false
	}
	return exists, err
}



// CreateMovieTable creates a DynamoDB table with a composite primary key defined as
// a string sort key named `title`, and a numeric partition key named `year`.
// This function uses NewTableExistsWaiter to wait for the table to be created by
// DynamoDB before it returns.
func (basics TableBasics) CreateMovieTable() (*types.TableDescription, error) {
	var tableDesc *types.TableDescription
	table, err := basics.DynamoDbClient.CreateTable(context.TODO(), &dynamodb.CreateTableInput{
		AttributeDefinitions: []types.AttributeDefinition{{
			AttributeName: aws.String("year"),
			AttributeType: types.ScalarAttributeTypeN,
		}, {
			AttributeName: aws.String("title"),
			AttributeType: types.ScalarAttributeTypeS,
		}},
		KeySchema: []types.KeySchemaElement{{
			AttributeName: aws.String("year"),
			KeyType:       types.KeyTypeHash,
		}, {
			AttributeName: aws.String("title"),
			KeyType:       types.KeyTypeRange,
		}},
		TableName: aws.String(basics.TableName),
		ProvisionedThroughput: &types.ProvisionedThroughput{
			ReadCapacityUnits:  aws.Int64(10),
			WriteCapacityUnits: aws.Int64(10),
		},
	})
	if err != nil {
		log.Printf("Couldn't create table %v. Here's why: %v\n", basics.TableName, err)
	} else {
		waiter := dynamodb.NewTableExistsWaiter(basics.DynamoDbClient)
		err = waiter.Wait(context.TODO(), &dynamodb.DescribeTableInput{
			TableName: aws.String(basics.TableName)}, 5*time.Minute)
		if err != nil {
			log.Printf("Wait for table exists failed. Here's why: %v\n", err)
		}
		tableDesc = table.TableDescription
	}
	return tableDesc, err
}



// ListTables lists the DynamoDB table names for the current account.
func (basics TableBasics) ListTables() ([]string, error) {
	var tableNames []string
	tables, err := basics.DynamoDbClient.ListTables(
		context.TODO(), &dynamodb.ListTablesInput{})
	if err != nil {
		log.Printf("Couldn't list tables. Here's why: %v\n", err)
	} else {
		tableNames = tables.TableNames
	}
	return tableNames, err
}



// AddMovie adds a movie the DynamoDB table.
func (basics TableBasics) AddMovie(movie Movie) error {
	item, err := attributevalue.MarshalMap(movie)
	if err != nil {
		panic(err)
	}
	_, err = basics.DynamoDbClient.PutItem(context.TODO(), &dynamodb.PutItemInput{
		TableName: aws.String(basics.TableName), Item: item,
	})
	if err != nil {
		log.Printf("Couldn't add item to table. Here's why: %v\n", err)
	}
	return err
}



// UpdateMovie updates the rating and plot of a movie that already exists in the
// DynamoDB table. This function uses the `expression` package to build the update
// expression.
func (basics TableBasics) UpdateMovie(movie Movie) (map[string]map[string]interface{}, error) {
	var err error
	var response *dynamodb.UpdateItemOutput
	var attributeMap map[string]map[string]interface{}
	update := expression.Set(expression.Name("info.rating"), expression.Value(movie.Info["rating"]))
	update.Set(expression.Name("info.plot"), expression.Value(movie.Info["plot"]))
	expr, err := expression.NewBuilder().WithUpdate(update).Build()
	if err != nil {
		log.Printf("Couldn't build expression for update. Here's why: %v\n", err)
	} else {
		response, err = basics.DynamoDbClient.UpdateItem(context.TODO(), &dynamodb.UpdateItemInput{
			TableName:                 aws.String(basics.TableName),
			Key:                       movie.GetKey(),
			ExpressionAttributeNames:  expr.Names(),
			ExpressionAttributeValues: expr.Values(),
			UpdateExpression:          expr.Update(),
			ReturnValues:              types.ReturnValueUpdatedNew,
		})
		if err != nil {
			log.Printf("Couldn't update movie %v. Here's why: %v\n", movie.Title, err)
		} else {
			err = attributevalue.UnmarshalMap(response.Attributes, &attributeMap)
			if err != nil {
				log.Printf("Couldn't unmarshall update response. Here's why: %v\n", err)
			}
		}
	}
	return attributeMap, err
}



// AddMovieBatch adds a slice of movies to the DynamoDB table. The function sends
// batches of 25 movies to DynamoDB until all movies are added or it reaches the
// specified maximum.
func (basics TableBasics) AddMovieBatch(movies []Movie, maxMovies int) (int, error) {
	var err error
	var item map[string]types.AttributeValue
	written := 0
	batchSize := 25 // DynamoDB allows a maximum batch size of 25 items.
	start := 0
	end := start + batchSize
	for start < maxMovies && start < len(movies) {
		var writeReqs []types.WriteRequest
		if end > len(movies) {
			end = len(movies)
		}
		for _, movie := range movies[start:end] {
			item, err = attributevalue.MarshalMap(movie)
			if err != nil {
				log.Printf("Couldn't marshal movie %v for batch writing. Here's why: %v\n", movie.Title, err)
			} else {
				writeReqs = append(
					writeReqs,
					types.WriteRequest{PutRequest: &types.PutRequest{Item: item}},
				)
			}
		}
		_, err = basics.DynamoDbClient.BatchWriteItem(context.TODO(), &dynamodb.BatchWriteItemInput{
			RequestItems: map[string][]types.WriteRequest{basics.TableName: writeReqs}})
		if err != nil {
			log.Printf("Couldn't add a batch of movies to %v. Here's why: %v\n", basics.TableName, err)
		} else {
			written += len(writeReqs)
		}
		start = end
		end += batchSize
	}

	return written, err
}



// GetMovie gets movie data from the DynamoDB table by using the primary composite key
// made of title and year.
func (basics TableBasics) GetMovie(title string, year int) (Movie, error) {
	movie := Movie{Title: title, Year: year}
	response, err := basics.DynamoDbClient.GetItem(context.TODO(), &dynamodb.GetItemInput{
		Key: movie.GetKey(), TableName: aws.String(basics.TableName),
	})
	if err != nil {
		log.Printf("Couldn't get info about %v. Here's why: %v\n", title, err)
	} else {
		err = attributevalue.UnmarshalMap(response.Item, &movie)
		if err != nil {
			log.Printf("Couldn't unmarshal response. Here's why: %v\n", err)
		}
	}
	return movie, err
}



// Query gets all movies in the DynamoDB table that were released in the specified year.
// The function uses the `expression` package to build the key condition expression
// that is used in the query.
func (basics TableBasics) Query(releaseYear int) ([]Movie, error) {
	var err error
	var response *dynamodb.QueryOutput
	var movies []Movie
	keyEx := expression.Key("year").Equal(expression.Value(releaseYear))
	expr, err := expression.NewBuilder().WithKeyCondition(keyEx).Build()
	if err != nil {
		log.Printf("Couldn't build epxression for query. Here's why: %v\n", err)
	} else {
		response, err = basics.DynamoDbClient.Query(context.TODO(), &dynamodb.QueryInput{
			TableName:                 aws.String(basics.TableName),
			ExpressionAttributeNames:  expr.Names(),
			ExpressionAttributeValues: expr.Values(),
			KeyConditionExpression:    expr.KeyCondition(),
		})
		if err != nil {
			log.Printf("Couldn't query for movies released in %v. Here's why: %v\n", releaseYear, err)
		} else {
			err = attributevalue.UnmarshalListOfMaps(response.Items, &movies)
			if err != nil {
				log.Printf("Couldn't unmarshal query response. Here's why: %v\n", err)
			}
		}
	}
	return movies, err
}



// Scan gets all movies in the DynamoDB table that were released in a range of years
// and projects them to return a reduced set of fields.
// The function uses the `expression` package to build the filter and projection
// expressions.
func (basics TableBasics) Scan(startYear int, endYear int) ([]Movie, error) {
	var movies []Movie
	var err error
	var response *dynamodb.ScanOutput
	filtEx := expression.Name("year").Between(expression.Value(startYear), expression.Value(endYear))
	projEx := expression.NamesList(
		expression.Name("year"), expression.Name("title"), expression.Name("info.rating"))
	expr, err := expression.NewBuilder().WithFilter(filtEx).WithProjection(projEx).Build()
	if err != nil {
		log.Printf("Couldn't build expressions for scan. Here's why: %v\n", err)
	} else {
		response, err = basics.DynamoDbClient.Scan(context.TODO(), &dynamodb.ScanInput{
			TableName:                 aws.String(basics.TableName),
			ExpressionAttributeNames:  expr.Names(),
			ExpressionAttributeValues: expr.Values(),
			FilterExpression:          expr.Filter(),
			ProjectionExpression:      expr.Projection(),
		})
		if err != nil {
			log.Printf("Couldn't scan for movies released between %v and %v. Here's why: %v\n",
				startYear, endYear, err)
		} else {
			err = attributevalue.UnmarshalListOfMaps(response.Items, &movies)
			if err != nil {
				log.Printf("Couldn't unmarshal query response. Here's why: %v\n", err)
			}
		}
	}
	return movies, err
}



// DeleteMovie removes a movie from the DynamoDB table.
func (basics TableBasics) DeleteMovie(movie Movie) error {
	_, err := basics.DynamoDbClient.DeleteItem(context.TODO(), &dynamodb.DeleteItemInput{
		TableName: aws.String(basics.TableName), Key: movie.GetKey(),
	})
	if err != nil {
		log.Printf("Couldn't delete %v from the table. Here's why: %v\n", movie.Title, err)
	}
	return err
}



// DeleteTable deletes the DynamoDB table and all of its data.
func (basics TableBasics) DeleteTable() error {
	_, err := basics.DynamoDbClient.DeleteTable(context.TODO(), &dynamodb.DeleteTableInput{
		TableName: aws.String(basics.TableName)})
	if err != nil {
		log.Printf("Couldn't delete table %v. Here's why: %v\n", basics.TableName, err)
	}
	return err
}

运行交互式场景以创建表并对其执行操作。

// RunMovieScenario is an interactive example that shows you how to use the AWS SDK for Go
// to create and use an Amazon DynamoDB table that stores data about movies.
//
//   1. Create a table that can hold movie data.
//   2. Put, get, and update a single movie in the table.
//   3. Write movie data to the table from a sample JSON file.
//   4. Query for movies that were released in a given year.
//   5. Scan for movies that were released in a range of years.
//   6. Delete a movie from the table.
//   7. Delete the table.
//
// This example creates a DynamoDB service client from the specified sdkConfig so that
// you can replace it with a mocked or stubbed config for unit testing.
//
// It uses a questioner from the `demotools` package to get input during the example.
// This package can be found in the ..\..\demotools folder of this repo.
//
// The specified movie sampler is used to get sample data from a URL that is loaded
// into the named table.
func RunMovieScenario(
	sdkConfig aws.Config, questioner demotools.IQuestioner, tableName string,
	movieSampler actions.IMovieSampler) {
	defer func() {
		if r := recover(); r != nil {
			fmt.Printf("Something went wrong with the demo.")
		}
	}()

	log.Println(strings.Repeat("-", 88))
	log.Println("Welcome to the Amazon DynamoDB getting started demo.")
	log.Println(strings.Repeat("-", 88))

	tableBasics := actions.TableBasics{TableName: tableName,
		DynamoDbClient: dynamodb.NewFromConfig(sdkConfig)}

	exists, err := tableBasics.TableExists()
	if err != nil {
		panic(err)
	}
	if !exists {
		log.Printf("Creating table %v...\n", tableName)
		_, err = tableBasics.CreateMovieTable()
		if err != nil {
			panic(err)
		} else {
			log.Printf("Created table %v.\n", tableName)
		}
	} else {
		log.Printf("Table %v already exists.\n", tableName)
	}

	var customMovie actions.Movie
	customMovie.Title = questioner.Ask("Enter a movie title to add to the table:",
		[]demotools.IAnswerValidator{demotools.NotEmpty{}})
	customMovie.Year = questioner.AskInt("What year was it released?",
		[]demotools.IAnswerValidator{demotools.NotEmpty{}, demotools.InIntRange{
			Lower: 1900, Upper: 2030}})
	customMovie.Info = map[string]interface{}{}
	customMovie.Info["rating"] = questioner.AskFloat64(
		"Enter a rating between 1 and 10:", []demotools.IAnswerValidator{
			demotools.NotEmpty{}, demotools.InFloatRange{Lower: 1, Upper: 10}})
	customMovie.Info["plot"] = questioner.Ask("What's the plot? ",
		[]demotools.IAnswerValidator{demotools.NotEmpty{}})
	err = tableBasics.AddMovie(customMovie)
	if err == nil {
		log.Printf("Added %v to the movie table.\n", customMovie.Title)
	}
	log.Println(strings.Repeat("-", 88))

	log.Printf("Let's update your movie. You previously rated it %v.\n", customMovie.Info["rating"])
	customMovie.Info["rating"] = questioner.AskFloat64(
		"What new rating would you give it?", []demotools.IAnswerValidator{
			demotools.NotEmpty{}, demotools.InFloatRange{Lower: 1, Upper: 10}})
	log.Printf("You summarized the plot as '%v'.\n", customMovie.Info["plot"])
	customMovie.Info["plot"] = questioner.Ask("What would you say now?",
		[]demotools.IAnswerValidator{demotools.NotEmpty{}})
	attributes, err := tableBasics.UpdateMovie(customMovie)
	if err == nil {
		log.Printf("Updated %v with new values.\n", customMovie.Title)
		for _, attVal := range attributes {
			for valKey, val := range attVal {
				log.Printf("\t%v: %v\n", valKey, val)
			}
		}
	}
	log.Println(strings.Repeat("-", 88))

	log.Printf("Getting movie data from %v and adding 250 movies to the table...\n",
		movieSampler.GetURL())
	movies := movieSampler.GetSampleMovies()
	written, err := tableBasics.AddMovieBatch(movies, 250)
	if err != nil {
		panic(err)
	} else {
		log.Printf("Added %v movies to the table.\n", written)
	}

	show := 10
	if show > written {
		show = written
	}
	log.Printf("The first %v movies in the table are:", show)
	for index, movie := range movies[:show] {
		log.Printf("\t%v. %v\n", index+1, movie.Title)
	}
	movieIndex := questioner.AskInt(
		"Enter the number of a movie to get info about it: ", []demotools.IAnswerValidator{
			demotools.InIntRange{Lower: 1, Upper: show}},
	)
	movie, err := tableBasics.GetMovie(movies[movieIndex-1].Title, movies[movieIndex-1].Year)
	if err == nil {
		log.Println(movie)
	}
	log.Println(strings.Repeat("-", 88))

	log.Println("Let's get a list of movies released in a given year.")
	releaseYear := questioner.AskInt("Enter a year between 1972 and 2018: ",
		[]demotools.IAnswerValidator{demotools.InIntRange{Lower: 1972, Upper: 2018}},
	)
	releases, err := tableBasics.Query(releaseYear)
	if err == nil {
		if len(releases) == 0 {
			log.Printf("I couldn't find any movies released in %v!\n", releaseYear)
		} else {
			for _, movie = range releases {
				log.Println(movie)
			}
		}
	}
	log.Println(strings.Repeat("-", 88))

	log.Println("Now let's scan for movies released in a range of years.")
	startYear := questioner.AskInt("Enter a year: ", []demotools.IAnswerValidator{
		demotools.InIntRange{Lower: 1972, Upper: 2018}})
	endYear := questioner.AskInt("Enter another year: ", []demotools.IAnswerValidator{
		demotools.InIntRange{Lower: 1972, Upper: 2018}})
	releases, err = tableBasics.Scan(startYear, endYear)
	if err == nil {
		if len(releases) == 0 {
			log.Printf("I couldn't find any movies released between %v and %v!\n", startYear, endYear)
		} else {
			log.Printf("Found %v movies. In this list, the plot is <nil> because "+
				"we used a projection expression when scanning for items to return only "+
				"the title, year, and rating.\n", len(releases))
			for _, movie = range releases {
				log.Println(movie)
			}
		}
	}
	log.Println(strings.Repeat("-", 88))

	var tables []string
	if questioner.AskBool("Do you want to list all of your tables? (y/n) ", "y") {
		tables, err = tableBasics.ListTables()
		if err == nil {
			log.Printf("Found %v tables:", len(tables))
			for _, table := range tables {
				log.Printf("\t%v", table)
			}
		}
	}
	log.Println(strings.Repeat("-", 88))

	log.Printf("Let's remove your movie '%v'.\n", customMovie.Title)
	if questioner.AskBool("Do you want to delete it from the table? (y/n) ", "y") {
		err = tableBasics.DeleteMovie(customMovie)
	}
	if err == nil {
		log.Printf("Deleted %v.\n", customMovie.Title)
	}

	if questioner.AskBool("Delete the table, too? (y/n)", "y") {
		err = tableBasics.DeleteTable()
	} else {
		log.Println("Don't forget to delete the table when you're done or you might " +
			"incur charges on your account.")
	}
	if err == nil {
		log.Printf("Deleted table %v.\n", tableBasics.TableName)
	}

	log.Println(strings.Repeat("-", 88))
	log.Println("Thanks for watching!")
	log.Println(strings.Repeat("-", 88))
}

创建 DynamoDB 表。

    // Create a table with a Sort key.
    public static void createTable(DynamoDbClient ddb, String tableName) {
        DynamoDbWaiter dbWaiter = ddb.waiter();
        ArrayList<AttributeDefinition> attributeDefinitions = new ArrayList<>();

        // Define attributes.
        attributeDefinitions.add(AttributeDefinition.builder()
            .attributeName("year")
            .attributeType("N")
            .build());

        attributeDefinitions.add(AttributeDefinition.builder()
            .attributeName("title")
            .attributeType("S")
            .build());

        ArrayList<KeySchemaElement> tableKey = new ArrayList<>();
        KeySchemaElement key = KeySchemaElement.builder()
            .attributeName("year")
            .keyType(KeyType.HASH)
            .build();

        KeySchemaElement key2 = KeySchemaElement.builder()
            .attributeName("title")
            .keyType(KeyType.RANGE)
            .build();

        // Add KeySchemaElement objects to the list.
        tableKey.add(key);
        tableKey.add(key2);

        CreateTableRequest request = CreateTableRequest.builder()
            .keySchema(tableKey)
            .provisionedThroughput(ProvisionedThroughput.builder()
                .readCapacityUnits(new Long(10))
                .writeCapacityUnits(new Long(10))
                .build())
            .attributeDefinitions(attributeDefinitions)
            .tableName(tableName)
            .build();

        try {
            CreateTableResponse response = ddb.createTable(request);
            DescribeTableRequest tableRequest = DescribeTableRequest.builder()
                .tableName(tableName)
                .build();

            // Wait until the Amazon DynamoDB table is created.
            WaiterResponse<DescribeTableResponse> waiterResponse = dbWaiter.waitUntilTableExists(tableRequest);
            waiterResponse.matched().response().ifPresent(System.out::println);
            String newTable = response.tableDescription().tableName();
            System.out.println("The " +newTable + " was successfully created.");

        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
    }

创建帮助函数以下载并提取示例 JSON 文件。

    // Load data into the table.
    public static void loadData(DynamoDbClient ddb, String tableName, String fileName) throws IOException {
        DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
            .dynamoDbClient(ddb)
            .build();

        DynamoDbTable<Movies> mappedTable = enhancedClient.table("Movies", TableSchema.fromBean(Movies.class));
        JsonParser parser = new JsonFactory().createParser(new File(fileName));
        com.fasterxml.jackson.databind.JsonNode rootNode = new ObjectMapper().readTree(parser);
        Iterator<JsonNode> iter = rootNode.iterator();
        ObjectNode currentNode;
        int t = 0 ;
        while (iter.hasNext()) {
            // Only add 200 Movies to the table.
            if (t == 200)
                break ;
            currentNode = (ObjectNode) iter.next();

            int year = currentNode.path("year").asInt();
            String title = currentNode.path("title").asText();
            String info = currentNode.path("info").toString();

            Movies movies = new Movies();
            movies.setYear(year);
            movies.setTitle(title);
            movies.setInfo(info);

            // Put the data into the Amazon DynamoDB Movie table.
            mappedTable.putItem(movies);
            t++;
        }
    }

从表中获取项目。

    public static void getItem(DynamoDbClient ddb) {

        HashMap<String,AttributeValue> keyToGet = new HashMap<>();
        keyToGet.put("year", AttributeValue.builder()
            .n("1933")
            .build());

        keyToGet.put("title", AttributeValue.builder()
            .s("King Kong")
            .build());

        GetItemRequest request = GetItemRequest.builder()
            .key(keyToGet)
            .tableName("Movies")
            .build();

        try {
            Map<String,AttributeValue> returnedItem = ddb.getItem(request).item();

            if (returnedItem != null) {
                Set<String> keys = returnedItem.keySet();
                System.out.println("Amazon DynamoDB table attributes: \n");

                for (String key1 : keys) {
                    System.out.format("%s: %s\n", key1, returnedItem.get(key1).toString());
                }
            } else {
                System.out.format("No item found with the key %s!\n", "year");
            }

        } catch (DynamoDbException e) {
             System.err.println(e.getMessage());
             System.exit(1);
        }
    }

完整示例。

/**
 *  Before running this Java V2 code example, set up your development environment, including your credentials.
 *
 *  For more information, see the following documentation topic:
 *
 *  https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html
 *
 *  This Java example performs these tasks:
 *
 * 1. Creates the Amazon DynamoDB Movie table with partition and sort key.
 * 2. Puts data into the Amazon DynamoDB table from a JSON document using the Enhanced client.
 * 3. Gets data from the Movie table.
 * 4. Adds a new item.
 * 5. Updates an item.
 * 6. Uses a Scan to query items using the Enhanced client.
 * 7. Queries all items where the year is 2013 using the Enhanced Client.
 * 8. Deletes the table.
 */

public class Scenario {
    public static final String DASHES = new String(new char[80]).replace("\0", "-");
    public static void main(String[] args) throws IOException {
        final String usage = "\n" +
            "Usage:\n" +
            "    <fileName>\n\n" +
            "Where:\n" +
            "    fileName - The path to the moviedata.json file that you can download from the Amazon DynamoDB Developer Guide.\n" ;

        if (args.length != 1) {
            System.out.println(usage);
            System.exit(1);
        }

        String tableName = "Movies";
        String fileName = args[0];
        ProfileCredentialsProvider credentialsProvider = ProfileCredentialsProvider.create();
        Region region = Region.US_EAST_1;
        DynamoDbClient ddb = DynamoDbClient.builder()
            .region(region)
            .credentialsProvider(credentialsProvider)
            .build();

        System.out.println(DASHES);
        System.out.println("Welcome to the Amazon DynamoDB example scenario.");
        System.out.println(DASHES);

        System.out.println(DASHES);
        System.out.println("1. Creating an Amazon DynamoDB table named Movies with a key named year and a sort key named title.");
        createTable(ddb, tableName);
        System.out.println(DASHES);

        System.out.println(DASHES);
        System.out.println("2. Loading data into the Amazon DynamoDB table.");
        loadData(ddb, tableName, fileName);
        System.out.println(DASHES);

        System.out.println(DASHES);
        System.out.println("3. Getting data from the Movie table.");
        getItem(ddb) ;
        System.out.println(DASHES);

        System.out.println(DASHES);
        System.out.println("4. Putting a record into the Amazon DynamoDB table.");
        putRecord(ddb);
        System.out.println(DASHES);

        System.out.println(DASHES);
        System.out.println("5. Updating a record.");
        updateTableItem(ddb, tableName);
        System.out.println(DASHES);

        System.out.println(DASHES);
        System.out.println("6. Scanning the Amazon DynamoDB table.");
        scanMovies(ddb, tableName);
        System.out.println(DASHES);

        System.out.println(DASHES);
        System.out.println("7. Querying the Movies released in 2013.");
        queryTable(ddb);
        System.out.println(DASHES);

        System.out.println(DASHES);
        System.out.println("8. Deleting the Amazon DynamoDB table.");
        deleteDynamoDBTable(ddb, tableName);
        System.out.println(DASHES);

        ddb.close();
    }

    // Create a table with a Sort key.
    public static void createTable(DynamoDbClient ddb, String tableName) {
        DynamoDbWaiter dbWaiter = ddb.waiter();
        ArrayList<AttributeDefinition> attributeDefinitions = new ArrayList<>();

        // Define attributes.
        attributeDefinitions.add(AttributeDefinition.builder()
            .attributeName("year")
            .attributeType("N")
            .build());

        attributeDefinitions.add(AttributeDefinition.builder()
            .attributeName("title")
            .attributeType("S")
            .build());

        ArrayList<KeySchemaElement> tableKey = new ArrayList<>();
        KeySchemaElement key = KeySchemaElement.builder()
            .attributeName("year")
            .keyType(KeyType.HASH)
            .build();

        KeySchemaElement key2 = KeySchemaElement.builder()
            .attributeName("title")
            .keyType(KeyType.RANGE)
            .build();

        // Add KeySchemaElement objects to the list.
        tableKey.add(key);
        tableKey.add(key2);

        CreateTableRequest request = CreateTableRequest.builder()
            .keySchema(tableKey)
            .provisionedThroughput(ProvisionedThroughput.builder()
                .readCapacityUnits(new Long(10))
                .writeCapacityUnits(new Long(10))
                .build())
            .attributeDefinitions(attributeDefinitions)
            .tableName(tableName)
            .build();

        try {
            CreateTableResponse response = ddb.createTable(request);
            DescribeTableRequest tableRequest = DescribeTableRequest.builder()
                .tableName(tableName)
                .build();

            // Wait until the Amazon DynamoDB table is created.
            WaiterResponse<DescribeTableResponse> waiterResponse = dbWaiter.waitUntilTableExists(tableRequest);
            waiterResponse.matched().response().ifPresent(System.out::println);
            String newTable = response.tableDescription().tableName();
            System.out.println("The " +newTable + " was successfully created.");

        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
    }

    // Query the table.
    public static void queryTable(DynamoDbClient ddb) {
        try {
            DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
                .dynamoDbClient(ddb)
                .build();

            DynamoDbTable<Movies> custTable = enhancedClient.table("Movies", TableSchema.fromBean(Movies.class));
            QueryConditional queryConditional = QueryConditional
                .keyEqualTo(Key.builder()
                .partitionValue(2013)
                .build());

            // Get items in the table and write out the ID value.
            Iterator<Movies> results = custTable.query(queryConditional).items().iterator();
            String result="";

            while (results.hasNext()) {
                Movies rec = results.next();
                System.out.println("The title of the movie is "+rec.getTitle());
                System.out.println("The movie information  is "+rec.getInfo());
            }

        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
            }
        }

        // Scan the table.
        public static void scanMovies(DynamoDbClient ddb, String tableName) {
            System.out.println("******* Scanning all movies.\n");
            try{
                DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
                        .dynamoDbClient(ddb)
                        .build();

                DynamoDbTable<Movies> custTable = enhancedClient.table("Movies", TableSchema.fromBean(Movies.class));
                Iterator<Movies> results = custTable.scan().items().iterator();
                while (results.hasNext()) {
                    Movies rec = results.next();
                    System.out.println("The movie title is "+rec.getTitle());
                    System.out.println("The movie year is " +rec.getYear());
                }

            } catch (DynamoDbException e) {
                System.err.println(e.getMessage());
                System.exit(1);
            }
        }

    // Load data into the table.
    public static void loadData(DynamoDbClient ddb, String tableName, String fileName) throws IOException {
        DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
            .dynamoDbClient(ddb)
            .build();

        DynamoDbTable<Movies> mappedTable = enhancedClient.table("Movies", TableSchema.fromBean(Movies.class));
        JsonParser parser = new JsonFactory().createParser(new File(fileName));
        com.fasterxml.jackson.databind.JsonNode rootNode = new ObjectMapper().readTree(parser);
        Iterator<JsonNode> iter = rootNode.iterator();
        ObjectNode currentNode;
        int t = 0 ;
        while (iter.hasNext()) {
            // Only add 200 Movies to the table.
            if (t == 200)
                break ;
            currentNode = (ObjectNode) iter.next();

            int year = currentNode.path("year").asInt();
            String title = currentNode.path("title").asText();
            String info = currentNode.path("info").toString();

            Movies movies = new Movies();
            movies.setYear(year);
            movies.setTitle(title);
            movies.setInfo(info);

            // Put the data into the Amazon DynamoDB Movie table.
            mappedTable.putItem(movies);
            t++;
        }
    }

    // Update the record to include show only directors.
    public static void updateTableItem(DynamoDbClient ddb, String tableName){
        HashMap<String,AttributeValue> itemKey = new HashMap<>();
        itemKey.put("year", AttributeValue.builder().n("1933").build());
        itemKey.put("title", AttributeValue.builder().s("King Kong").build());

        HashMap<String,AttributeValueUpdate> updatedValues = new HashMap<>();
        updatedValues.put("info", AttributeValueUpdate.builder()
            .value(AttributeValue.builder().s("{\"directors\":[\"Merian C. Cooper\",\"Ernest B. Schoedsack\"]").build())
            .action(AttributeAction.PUT)
            .build());

        UpdateItemRequest request = UpdateItemRequest.builder()
            .tableName(tableName)
            .key(itemKey)
            .attributeUpdates(updatedValues)
            .build();

        try {
            ddb.updateItem(request);
        } catch (ResourceNotFoundException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }

        System.out.println("Item was updated!");
    }

    public static void deleteDynamoDBTable(DynamoDbClient ddb, String tableName) {
        DeleteTableRequest request = DeleteTableRequest.builder()
            .tableName(tableName)
            .build();

        try {
            ddb.deleteTable(request);

        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
        System.out.println(tableName +" was successfully deleted!");
    }

    public static void putRecord(DynamoDbClient ddb) {
        try {
            DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
                .dynamoDbClient(ddb)
                .build();

            DynamoDbTable<Movies> table = enhancedClient.table("Movies", TableSchema.fromBean(Movies.class));

            // Populate the Table.
            Movies record = new Movies();
            record.setYear(2020);
            record.setTitle("My Movie2");
            record.setInfo("no info");
            table.putItem(record);

        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
        System.out.println("Added a new movie to the table.");
    }

    public static void getItem(DynamoDbClient ddb) {

        HashMap<String,AttributeValue> keyToGet = new HashMap<>();
        keyToGet.put("year", AttributeValue.builder()
            .n("1933")
            .build());

        keyToGet.put("title", AttributeValue.builder()
            .s("King Kong")
            .build());

        GetItemRequest request = GetItemRequest.builder()
            .key(keyToGet)
            .tableName("Movies")
            .build();

        try {
            Map<String,AttributeValue> returnedItem = ddb.getItem(request).item();

            if (returnedItem != null) {
                Set<String> keys = returnedItem.keySet();
                System.out.println("Amazon DynamoDB table attributes: \n");

                for (String key1 : keys) {
                    System.out.format("%s: %s\n", key1, returnedItem.get(key1).toString());
                }
            } else {
                System.out.format("No item found with the key %s!\n", "year");
            }

        } catch (DynamoDbException e) {
             System.err.println(e.getMessage());
             System.exit(1);
        }
    }
}

创建 DynamoDB 客户端。

// Create the DynamoDB service client module using ES6 syntax.
import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { DEFAULT_REGION } from "../../../../libs/utils/util-aws-sdk.js";
// Create an Amazon DynamoDB service client object.
export const ddbClient = new DynamoDBClient({ region: DEFAULT_REGION });

创建 DynamoDB 文档客户端。

// Create a service client module using ES6 syntax.
import { DynamoDBDocumentClient } from "@aws-sdk/lib-dynamodb";
import { ddbClient } from "./ddbClient.js";

const marshallOptions = {
  // Whether to automatically convert empty strings, blobs, and sets to `null`.
  convertEmptyValues: false, // false, by default.
  // Whether to remove undefined values while marshalling.
  removeUndefinedValues: true, // false, by default.
  // Whether to convert typeof object to map attribute.
  convertClassInstanceToMap: false, // false, by default.
};

const unmarshallOptions = {
  // Whether to return numbers as a string instead of converting them to native JavaScript numbers.
  wrapNumbers: false, // false, by default.
};

// Create the DynamoDB document client.
const ddbDocClient = DynamoDBDocumentClient.from(ddbClient, {
  marshallOptions,
  unmarshallOptions,
});

export { ddbDocClient };

运行场景。

import fs from "fs";
import { splitEvery } from "ramda";
import {
  PutCommand,
  GetCommand,
  UpdateCommand,
  BatchWriteCommand,
  DeleteCommand,
  ScanCommand,
  QueryCommand,
} from "@aws-sdk/lib-dynamodb";
import {
  CreateTableCommand,
  DeleteTableCommand,
  waitUntilTableExists,
  waitUntilTableNotExists,
} from "@aws-sdk/client-dynamodb";

import { ddbClient } from "../libs/ddbClient.js";
import { ddbDocClient } from "../libs/ddbDocClient.js";

/**
 * @param {string} tableName
 */
const createTable = async (tableName) => {
  await ddbClient.send(
    new CreateTableCommand({
      AttributeDefinitions: [
        {
          AttributeName: "year",
          AttributeType: "N",
        },
        {
          AttributeName: "title",
          AttributeType: "S",
        },
      ],
      KeySchema: [
        {
          AttributeName: "year",
          KeyType: "HASH",
        },
        {
          AttributeName: "title",
          KeyType: "RANGE",
        },
      ],
      // Enables "on-demand capacity mode".
      BillingMode: "PAY_PER_REQUEST",
      TableName: tableName,
    })
  );
  await waitUntilTableExists(
    { client: ddbClient, maxWaitTime: 15, maxDelay: 2, minDelay: 1 },
    { TableName: tableName }
  );
};

/**
 *
 * @param {string} tableName
 * @param {Record<string, any> | undefined} attributes
 */
const putItem = async (tableName, attributes) => {
  const command = new PutCommand({
    TableName: tableName,
    Item: attributes,
  });

  await ddbDocClient.send(command);
};

/**
 *
 * @param {string} tableName
 * @param {string} filePath
 * @returns { { movieCount: number } } The number of movies written to the database.
 */
const batchWriteMoviesFromFile = async (tableName, filePath) => {
  const fileContents = fs.readFileSync(filePath);
  const movies = JSON.parse(fileContents, "utf8");

  // Map movies to RequestItems.
  const putMovieRequestItems = movies.map(({ year, title, info }) => ({
    PutRequest: { Item: { year, title, info } },
  }));

  // Organize RequestItems into batches of 25. 25 is the max number of items in a batch request.
  const putMovieBatches = splitEvery(25, putMovieRequestItems);
  const batchCount = putMovieBatches.length;

  // Map batches to promises.
  const batchRequests = putMovieBatches.map(async (batch, i) => {
    const command = new BatchWriteCommand({
      RequestItems: {
        [tableName]: batch,
      },
    });

    await ddbDocClient.send(command).then(() => {
      console.log(
        `Wrote batch ${i + 1} of ${batchCount} with ${batch.length} items.`
      );
    });
  });

  // Wait for all batch requests to resolve.
  await Promise.all(batchRequests);

  return { movieCount: movies.length };
};

/**
 *
 * @param {string} tableName
 * @param {{
 * existingMovieName: string,
 * existingMovieYear: string,
 * newMoviePlot: string,
 * newMovieRank: string}} keyUpdate
 */
const updateMovie = async (
  tableName,
  { existingMovieName, existingMovieYear, newMoviePlot, newMovieRank }
) => {
  await ddbClient.send(
    new UpdateCommand({
      TableName: tableName,
      Key: {
        title: existingMovieName,
        year: existingMovieYear,
      },
      // Define expressions for the new or updated attributes.
      ExpressionAttributeNames: { "#r": "rank" },
      UpdateExpression: "set info.plot = :p, info.#r = :r",
      ExpressionAttributeValues: {
        ":p": newMoviePlot,
        ":r": newMovieRank,
      },
      ReturnValues: "ALL_NEW",
    })
  );
};

/**
 * @param {{ title: string, info: { plot: string, rank: number }, year: number }} movie
 */
const logMovie = (movie) => {
  console.log(` | Title: "${movie.title}".`);
  console.log(` | Plot: "${movie.info.plot}`);
  console.log(` | Year: ${movie.year}`);
  console.log(` | Rank: ${movie.info.rank}`);
};

/**
 *
 * @param {{ title: string, info: { plot: string, rank: number }, year: number }[]} movies
 */
const logMovies = (movies) => {
  console.log("\n");
  movies.forEach((movie, i) => {
    if (i > 0) {
      console.log("-".repeat(80));
    }

    logMovie(movie);
  });
};

/**
 *
 * @param {string} tableName
 * @param {string} title
 * @param {number} year
 * @returns
 */
const getMovie = async (tableName, title, year) => {
  const { Item } = await ddbDocClient.send(
    new GetCommand({
      TableName: tableName,
      Key: {
        title,
        year
      },
      // By default, reads are eventually consistent. "ConsistentRead: true" represents
      // a strongly consistent read. This guarantees that the most up-to-date data is returned. It
      // can also result in higher latency and a potential for server errors.
      ConsistentRead: true,
    })
  );

  return Item;
};

/**
 *
 * @param {string} tableName
 * @param {{ title: string, year: number }} key
 */
const deleteMovie = async (tableName, key) => {
  await ddbDocClient.send(
    new DeleteCommand({
      TableName: tableName,
      Key: key,
    })
  );
};

/**
 *
 * @param {string} tableName
 * @param {number} startYear
 * @param {number} endYear
 * @param {Record<string, any>} startKey
 * @returns {Promise<{}[]>}
 */
const findMoviesBetweenYears = async (
  tableName,
  startYear,
  endYear,
  startKey = undefined
) => {
  const { Items, LastEvaluatedKey } = await ddbClient.send(
    new ScanCommand({
      ConsistentRead: true,
      TableName: tableName,
      ExpressionAttributeNames: { "#y": "year" },
      FilterExpression: "#y BETWEEN :y1 AND :y2",
      ExpressionAttributeValues: { ":y1": startYear, ":y2": endYear },
      ExclusiveStartKey: startKey,
    })
  );

  if (LastEvaluatedKey) {
    return Items.concat(
      await findMoviesBetweenYears(
        tableName,
        startYear,
        endYear,
        LastEvaluatedKey
      )
    );
  } else {
    return Items;
  }
};

/**
 *
 * @param {string} tableName
 * @param {number} year
 * @returns
 */
const queryMoviesByYear = async (tableName, year) => {
  const command = new QueryCommand({
    ConsistentRead: true,
    ExpressionAttributeNames: { "#y": "year" },
    TableName: tableName,
    ExpressionAttributeValues: {
      ":y": year,
    },
    KeyConditionExpression: "#y = :y",
  });

  const { Items } = await ddbDocClient.send(command);

  return Items;
};

/**
 *
 * @param {*} tableName
 */
const deleteTable = async (tableName) => {
  await ddbDocClient.send(new DeleteTableCommand({ TableName: tableName }));
  await waitUntilTableNotExists(
    {
      client: ddbClient,
      maxWaitTime: 10,
      maxDelay: 2,
      minDelay: 1,
    },
    { TableName: tableName }
  );
};
export const runScenario = async ({
  tableName,
  newMovieName,
  newMovieYear,
  existingMovieName,
  existingMovieYear,
  newMovieRank,
  newMoviePlot,
  moviesPath,
}) => {
  console.log(`Creating table named: ${tableName}`);
  await createTable(tableName);
  console.log(`\nTable created.`);

  console.log(`\nAdding "${newMovieName}" to ${tableName}.`);
  await putItem(tableName, { title: newMovieName, year: newMovieYear });
  console.log("\nSuccess - single movie added.");

  console.log("\nWriting hundreds of movies in batches.");
  const { movieCount } = await batchWriteMoviesFromFile(tableName, moviesPath);
  console.log(`\nWrote ${movieCount} movies to database.`);

  console.log(`\nGetting "${existingMovieName}."`);
  const originalMovie = await getMovie(
    tableName,
    existingMovieName,
    existingMovieYear
  );
  logMovie(originalMovie);

  console.log(`\nUpdating "${existingMovieName}" with a new plot and rank.`);
  await updateMovie(tableName, {
    existingMovieName,
    existingMovieYear,
    newMoviePlot,
    newMovieRank,
  });
  console.log(`\n"${existingMovieName}" updated.`);

  console.log(`\nGetting latest info for "${existingMovieName}"`);
  const updatedMovie = await getMovie(
    tableName,
    existingMovieName,
    existingMovieYear
  );
  logMovie(updatedMovie);

  console.log(`\nDeleting "${newMovieName}."`);
  await deleteMovie(tableName, { title: newMovieName, year: newMovieYear });
  console.log(`\n"${newMovieName} deleted.`);

  const [scanY1, scanY2] = [1985, 2003];
  console.log(
    `\nScanning ${tableName} for movies that premiered between ${scanY1} and ${scanY2}.`
  );
  const scannedMovies = await findMoviesBetweenYears(tableName, scanY1, scanY1);
  logMovies(scannedMovies);

  const queryY = 2003;
  console.log(`Querying ${tableName} for movies that premiered in ${queryY}.`);
  const queriedMovies = await queryMoviesByYear(tableName, queryY);
  logMovies(queriedMovies);

  console.log(`Deleting ${tableName}.`);
  await deleteTable(tableName);
  console.log(`${tableName} deleted.`);
};

const main = async () => {
  const args = {
    tableName: "myNewTable",
    newMovieName: "myMovieName",
    newMovieYear: 2022,
    existingMovieName: "This Is the End",
    existingMovieYear: 2013,
    newMovieRank: 200,
    newMoviePlot: "A coder cracks code...",
    moviesPath: "../../../../../../resources/sample_files/movies.json",
  };

  try {
    await runScenario(args);
  } catch (err) {
    // Some extra error handling here to be sure the table is cleaned up if something
    // goes wrong during the scenario run.

    console.error(err);

    const tableName = args.tableName;

    if (tableName) {
      console.log(`Attempting to delete ${tableName}`);
      await ddbClient
        .send(new DeleteTableCommand({ TableName: tableName }))
        .then(() => console.log(`\n${tableName} deleted.`))
        .catch((err) => console.error(`\nFailed to delete ${tableName}.`, err));
    }
  }
};

export { main };

创建 DynamoDB 表。

suspend fun createScenarioTable(tableNameVal: String, key: String) {

    val attDef = AttributeDefinition {
        attributeName = key
        attributeType = ScalarAttributeType.N
    }

    val attDef1 = AttributeDefinition {
        attributeName = "title"
        attributeType = ScalarAttributeType.S
    }

    val keySchemaVal = KeySchemaElement {
        attributeName = key
        keyType = KeyType.Hash
    }

    val keySchemaVal1 = KeySchemaElement {
        attributeName = "title"
        keyType = KeyType.Range
    }

    val provisionedVal = ProvisionedThroughput {
        readCapacityUnits = 10
        writeCapacityUnits = 10
    }

    val request = CreateTableRequest {
        attributeDefinitions = listOf(attDef, attDef1)
        keySchema = listOf(keySchemaVal, keySchemaVal1)
        provisionedThroughput = provisionedVal
        tableName = tableNameVal
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->

        val response = ddb.createTable(request)
        ddb.waitUntilTableExists { // suspend call
            tableName = tableNameVal
        }
        println("The table was successfully created ${response.tableDescription?.tableArn}")
    }
}

创建帮助函数以下载并提取示例 JSON 文件。

// Load data into the table.
suspend fun loadData(tableName: String, fileName: String) {

    val parser = JsonFactory().createParser(File(fileName))
    val rootNode = ObjectMapper().readTree<JsonNode>(parser)
    val iter: Iterator<JsonNode> = rootNode.iterator()
    var currentNode: ObjectNode

    var t = 0
    while (iter.hasNext()) {

        if (t == 50)
            break

        currentNode = iter.next() as ObjectNode
        val year = currentNode.path("year").asInt()
        val title = currentNode.path("title").asText()
        val info = currentNode.path("info").toString()
        putMovie(tableName, year, title, info)
        t++
    }
}

suspend fun putMovie(
    tableNameVal: String,
    year: Int,
    title: String,
    info: String
) {
    val itemValues = mutableMapOf<String, AttributeValue>()
    val strVal = year.toString()
    // Add all content to the table.
    itemValues["year"] = AttributeValue.N(strVal)
    itemValues["title"] = AttributeValue.S(title)
    itemValues["info"] = AttributeValue.S(info)

    val request = PutItemRequest {
        tableName = tableNameVal
        item = itemValues
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->
        ddb.putItem(request)
        println("Added $title to the Movie table.")
    }
}

从表中获取项目。

suspend fun getMovie(tableNameVal: String, keyName: String, keyVal: String) {

    val keyToGet = mutableMapOf<String, AttributeValue>()
    keyToGet[keyName] = AttributeValue.N(keyVal)
    keyToGet["title"] = AttributeValue.S("King Kong")

    val request = GetItemRequest {
        key = keyToGet
        tableName = tableNameVal
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->
        val returnedItem = ddb.getItem(request)
        val numbersMap = returnedItem.item
        numbersMap?.forEach { key1 ->
            println(key1.key)
            println(key1.value)
        }
    }
}

完整示例。

suspend fun main(args: Array<String>) {

    val usage = """
        Usage:
          <fileName>

        Where:
           fileName - The path to the moviedata.json you can download from the Amazon DynamoDB Developer Guide.
    """

    if (args.size != 1) {
        println(usage)
        exitProcess(1)
    }

    // Get the moviedata.json from the Amazon DynamoDB Developer Guide.
    val tableName = "Movies"
    val fileName = args[0]
    val partitionAlias = "#a"

    println("Creating an Amazon DynamoDB table named Movies with a key named id and a sort key named title.")
    createScenarioTable(tableName, "year")
    loadData(tableName, fileName)
    getMovie(tableName, "year", "1933")
    scanMovies(tableName)
    val count = queryMovieTable(tableName, "year", partitionAlias)
    println("There are $count Movies released in 2013.")
    deletIssuesTable(tableName)
}

suspend fun createScenarioTable(tableNameVal: String, key: String) {

    val attDef = AttributeDefinition {
        attributeName = key
        attributeType = ScalarAttributeType.N
    }

    val attDef1 = AttributeDefinition {
        attributeName = "title"
        attributeType = ScalarAttributeType.S
    }

    val keySchemaVal = KeySchemaElement {
        attributeName = key
        keyType = KeyType.Hash
    }

    val keySchemaVal1 = KeySchemaElement {
        attributeName = "title"
        keyType = KeyType.Range
    }

    val provisionedVal = ProvisionedThroughput {
        readCapacityUnits = 10
        writeCapacityUnits = 10
    }

    val request = CreateTableRequest {
        attributeDefinitions = listOf(attDef, attDef1)
        keySchema = listOf(keySchemaVal, keySchemaVal1)
        provisionedThroughput = provisionedVal
        tableName = tableNameVal
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->

        val response = ddb.createTable(request)
        ddb.waitUntilTableExists { // suspend call
            tableName = tableNameVal
        }
        println("The table was successfully created ${response.tableDescription?.tableArn}")
    }
}

// Load data into the table.
suspend fun loadData(tableName: String, fileName: String) {

    val parser = JsonFactory().createParser(File(fileName))
    val rootNode = ObjectMapper().readTree<JsonNode>(parser)
    val iter: Iterator<JsonNode> = rootNode.iterator()
    var currentNode: ObjectNode

    var t = 0
    while (iter.hasNext()) {

        if (t == 50)
            break

        currentNode = iter.next() as ObjectNode
        val year = currentNode.path("year").asInt()
        val title = currentNode.path("title").asText()
        val info = currentNode.path("info").toString()
        putMovie(tableName, year, title, info)
        t++
    }
}

suspend fun putMovie(
    tableNameVal: String,
    year: Int,
    title: String,
    info: String
) {
    val itemValues = mutableMapOf<String, AttributeValue>()
    val strVal = year.toString()
    // Add all content to the table.
    itemValues["year"] = AttributeValue.N(strVal)
    itemValues["title"] = AttributeValue.S(title)
    itemValues["info"] = AttributeValue.S(info)

    val request = PutItemRequest {
        tableName = tableNameVal
        item = itemValues
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->
        ddb.putItem(request)
        println("Added $title to the Movie table.")
    }
}

suspend fun getMovie(tableNameVal: String, keyName: String, keyVal: String) {

    val keyToGet = mutableMapOf<String, AttributeValue>()
    keyToGet[keyName] = AttributeValue.N(keyVal)
    keyToGet["title"] = AttributeValue.S("King Kong")

    val request = GetItemRequest {
        key = keyToGet
        tableName = tableNameVal
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->
        val returnedItem = ddb.getItem(request)
        val numbersMap = returnedItem.item
        numbersMap?.forEach { key1 ->
            println(key1.key)
            println(key1.value)
        }
    }
}

suspend fun deletIssuesTable(tableNameVal: String) {

    val request = DeleteTableRequest {
        tableName = tableNameVal
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->
        ddb.deleteTable(request)
        println("$tableNameVal was deleted")
    }
}

suspend fun queryMovieTable(
    tableNameVal: String,
    partitionKeyName: String,
    partitionAlias: String
): Int {

    val attrNameAlias = mutableMapOf<String, String>()
    attrNameAlias[partitionAlias] = "year"

    // Set up mapping of the partition name with the value.
    val attrValues = mutableMapOf<String, AttributeValue>()
    attrValues[":$partitionKeyName"] = AttributeValue.N("2013")

    val request = QueryRequest {
        tableName = tableNameVal
        keyConditionExpression = "$partitionAlias = :$partitionKeyName"
        expressionAttributeNames = attrNameAlias
        this.expressionAttributeValues = attrValues
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->
        val response = ddb.query(request)
        return response.count
    }
}

suspend fun scanMovies(tableNameVal: String) {

    val request = ScanRequest {
        tableName = tableNameVal
    }

    DynamoDbClient { region = "us-east-1" }.use { ddb ->
        val response = ddb.scan(request)
        response.items?.forEach { item ->
            item.keys.forEach { key ->
                println("The key name is $key\n")
                println("The value is ${item[key]}")
            }
        }
    }
}

namespace DynamoDb\Basics;

use Aws\DynamoDb\Marshaler;
use DynamoDb;
use DynamoDb\DynamoDBAttribute;
use DynamoDb\DynamoDBService;

class GettingStartedWithDynamoDB
{
    public function run()
    {
        echo("--------------------------------------\n");
        print("Welcome to the Amazon DynamoDB getting started demo using PHP!\n");
        echo("--------------------------------------\n");

        $uuid = uniqid();
        $service = new DynamoDBService();

        $tableName = "ddb_demo_table_$uuid";
        $service->createTable(
            $tableName,
            [
                new DynamoDBAttribute('year', 'N', 'HASH'),
                new DynamoDBAttribute('title', 'S', 'RANGE')
            ]
        );

        echo "Waiting for table...";
        $service->dynamoDbClient->waitUntil("TableExists", ['TableName' => $tableName]);
        echo "table $tableName found!\n";

        echo "What's the name of the last movie you watched?\n";
        while (empty($movieName)) {
            $movieName = testable_readline("Movie name: ");
        }
        echo "And what year was it released?\n";
        $movieYear = "year";
        while (!is_numeric($movieYear) || intval($movieYear) != $movieYear) {
            $movieYear = testable_readline("Year released: ");
        }

        $service->putItem([
            'Item' => [
                'year' => [
                    'N' => "$movieYear",
                ],
                'title' => [
                    'S' => $movieName,
                ],
            ],
            'TableName' => $tableName,
        ]);

        echo "How would you rate the movie from 1-10?\n";
        $rating = 0;
        while (!is_numeric($rating) || intval($rating) != $rating || $rating < 1 || $rating > 10) {
            $rating = testable_readline("Rating (1-10): ");
        }
        echo "What was the movie about?\n";
        while (empty($plot)) {
            $plot = testable_readline("Plot summary: ");
        }
        $key = [
            'Item' => [
                'title' => [
                    'S' => $movieName,
                ],
                'year' => [
                    'N' => $movieYear,
                ],
            ]
        ];
        $attributes = ["rating" =>
            [
                'AttributeName' => 'rating',
                'AttributeType' => 'N',
                'Value' => $rating,
            ],
            'plot' => [
                'AttributeName' => 'plot',
                'AttributeType' => 'S',
                'Value' => $plot,
            ]
        ];
        $service->updateItemAttributesByKey($tableName, $key, $attributes);
        echo "Movie added and updated.";

        $batch = json_decode(loadMovieData());

        $limit = 0;
        $service->writeBatch($tableName, $batch);


        $movie = $service->getItemByKey($tableName, $key);
        echo "\nThe movie {$movie['Item']['title']['S']} was released in {$movie['Item']['year']['N']}.\n";
        echo "What rating would you like to give {$movie['Item']['title']['S']}?\n";
        $rating = 0;
        while (!is_numeric($rating) || intval($rating) != $rating || $rating < 1 || $rating > 10) {
            $rating = testable_readline("Rating (1-10): ");
        }
        $service->updateItemAttributeByKey($tableName, $key, 'rating', 'N', $rating);

        $movie = $service->getItemByKey($tableName, $key);
        echo "Ok, you have rated {$movie['Item']['title']['S']} as a {$movie['Item']['rating']['N']}\n";

        $service->deleteItemByKey($tableName, $key);
        echo "But, bad news, this was a trap. That movie has now been deleted because of your rating...harsh.\n";

        echo "That's okay though. The book was better. Now, for something lighter, in what year were you born?\n";
        $birthYear = "not a number";
        while (!is_numeric($birthYear) || $birthYear >= date("Y")) {
            $birthYear = testable_readline("Birth year: ");
        }
        $birthKey = [
            'Key' => [
                'year' => [
                    'N' => "$birthYear",
                ],
            ],
        ];
        $result = $service->query($tableName, $birthKey);
        $marshal = new Marshaler();
        echo "Here are the movies in our collection released the year you were born:\n";
        $oops = "Oops! There were no movies released in that year (that we know of).\n";
        $display = "";
        foreach ($result['Items'] as $movie) {
            $movie = $marshal->unmarshalItem($movie);
            $display .= $movie['title'] . "\n";
        }
        echo ($display) ?: $oops;

        $yearsKey = [
            'Key' => [
                'year' => [
                    'N' => [
                        'minRange' => 1990,
                        'maxRange' => 1999,
                    ],
                ],
            ],
        ];
        $filter = "year between 1990 and 1999";
        echo "\nHere's a list of all the movies released in the 90s:\n";
        $result = $service->scan($tableName, $yearsKey, $filter);
        foreach ($result['Items'] as $movie) {
            $movie = $marshal->unmarshalItem($movie);
            echo $movie['title'] . "\n";
        }

        echo "\nCleaning up this demo by deleting table $tableName...\n";
        $service->deleteTable($tableName);
    }
}

创建封装 DynamoDB 表的类。

from decimal import Decimal
from io import BytesIO
import json
import logging
import os
from pprint import pprint
import requests
from zipfile import ZipFile
import boto3
from boto3.dynamodb.conditions import Key
from botocore.exceptions import ClientError
from question import Question

logger = logging.getLogger(__name__)

class Movies:
    """Encapsulates an Amazon DynamoDB table of movie data."""
    def __init__(self, dyn_resource):
        """
        :param dyn_resource: A Boto3 DynamoDB resource.
        """
        self.dyn_resource = dyn_resource
        self.table = None

    def exists(self, table_name):
        """
        Determines whether a table exists. As a side effect, stores the table in
        a member variable.

        :param table_name: The name of the table to check.
        :return: True when the table exists; otherwise, False.
        """
        try:
            table = self.dyn_resource.Table(table_name)
            table.load()
            exists = True
        except ClientError as err:
            if err.response['Error']['Code'] == 'ResourceNotFoundException':
                exists = False
            else:
                logger.error(
                    "Couldn't check for existence of %s. Here's why: %s: %s",
                    table_name,
                    err.response['Error']['Code'], err.response['Error']['Message'])
                raise
        else:
            self.table = table
        return exists

    def create_table(self, table_name):
        """
        Creates an Amazon DynamoDB table that can be used to store movie data.
        The table uses the release year of the movie as the partition key and the
        title as the sort key.

        :param table_name: The name of the table to create.
        :return: The newly created table.
        """
        try:
            self.table = self.dyn_resource.create_table(
                TableName=table_name,
                KeySchema=[
                    {'AttributeName': 'year', 'KeyType': 'HASH'},  # Partition key
                    {'AttributeName': 'title', 'KeyType': 'RANGE'}  # Sort key
                ],
                AttributeDefinitions=[
                    {'AttributeName': 'year', 'AttributeType': 'N'},
                    {'AttributeName': 'title', 'AttributeType': 'S'}
                ],
                ProvisionedThroughput={'ReadCapacityUnits': 10, 'WriteCapacityUnits': 10})
            self.table.wait_until_exists()
        except ClientError as err:
            logger.error(
                "Couldn't create table %s. Here's why: %s: %s", table_name,
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise
        else:
            return self.table

    def list_tables(self):
        """
        Lists the Amazon DynamoDB tables for the current account.

        :return: The list of tables.
        """
        try:
            tables = []
            for table in self.dyn_resource.tables.all():
                print(table.name)
                tables.append(table)
        except ClientError as err:
            logger.error(
                "Couldn't list tables. Here's why: %s: %s",
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise
        else:
            return tables

    def write_batch(self, movies):
        """
        Fills an Amazon DynamoDB table with the specified data, using the Boto3
        Table.batch_writer() function to put the items in the table.
        Inside the context manager, Table.batch_writer builds a list of
        requests. On exiting the context manager, Table.batch_writer starts sending
        batches of write requests to Amazon DynamoDB and automatically
        handles chunking, buffering, and retrying.

        :param movies: The data to put in the table. Each item must contain at least
                       the keys required by the schema that was specified when the
                       table was created.
        """
        try:
            with self.table.batch_writer() as writer:
                for movie in movies:
                    writer.put_item(Item=movie)
        except ClientError as err:
            logger.error(
                "Couldn't load data into table %s. Here's why: %s: %s", self.table.name,
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise

    def add_movie(self, title, year, plot, rating):
        """
        Adds a movie to the table.

        :param title: The title of the movie.
        :param year: The release year of the movie.
        :param plot: The plot summary of the movie.
        :param rating: The quality rating of the movie.
        """
        try:
            self.table.put_item(
                Item={
                    'year': year,
                    'title': title,
                    'info': {'plot': plot, 'rating': Decimal(str(rating))}})
        except ClientError as err:
            logger.error(
                "Couldn't add movie %s to table %s. Here's why: %s: %s",
                title, self.table.name,
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise

    def get_movie(self, title, year):
        """
        Gets movie data from the table for a specific movie.

        :param title: The title of the movie.
        :param year: The release year of the movie.
        :return: The data about the requested movie.
        """
        try:
            response = self.table.get_item(Key={'year': year, 'title': title})
        except ClientError as err:
            logger.error(
                "Couldn't get movie %s from table %s. Here's why: %s: %s",
                title, self.table.name,
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise
        else:
            return response['Item']

    def update_movie(self, title, year, rating, plot):
        """
        Updates rating and plot data for a movie in the table.

        :param title: The title of the movie to update.
        :param year: The release year of the movie to update.
        :param rating: The updated rating to the give the movie.
        :param plot: The updated plot summary to give the movie.
        :return: The fields that were updated, with their new values.
        """
        try:
            response = self.table.update_item(
                Key={'year': year, 'title': title},
                UpdateExpression="set info.rating=:r, info.plot=:p",
                ExpressionAttributeValues={
                    ':r': Decimal(str(rating)), ':p': plot},
                ReturnValues="UPDATED_NEW")
        except ClientError as err:
            logger.error(
                "Couldn't update movie %s in table %s. Here's why: %s: %s",
                title, self.table.name,
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise
        else:
            return response['Attributes']

    def query_movies(self, year):
        """
        Queries for movies that were released in the specified year.

        :param year: The year to query.
        :return: The list of movies that were released in the specified year.
        """
        try:
            response = self.table.query(KeyConditionExpression=Key('year').eq(year))
        except ClientError as err:
            logger.error(
                "Couldn't query for movies released in %s. Here's why: %s: %s", year,
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise
        else:
            return response['Items']

    def scan_movies(self, year_range):
        """
        Scans for movies that were released in a range of years.
        Uses a projection expression to return a subset of data for each movie.

        :param year_range: The range of years to retrieve.
        :return: The list of movies released in the specified years.
        """
        movies = []
        scan_kwargs = {
            'FilterExpression': Key('year').between(year_range['first'], year_range['second']),
            'ProjectionExpression': "#yr, title, info.rating",
            'ExpressionAttributeNames': {"#yr": "year"}}
        try:
            done = False
            start_key = None
            while not done:
                if start_key:
                    scan_kwargs['ExclusiveStartKey'] = start_key
                response = self.table.scan(**scan_kwargs)
                movies.extend(response.get('Items', []))
                start_key = response.get('LastEvaluatedKey', None)
                done = start_key is None
        except ClientError as err:
            logger.error(
                "Couldn't scan for movies. Here's why: %s: %s",
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise

        return movies

    def delete_movie(self, title, year):
        """
        Deletes a movie from the table.

        :param title: The title of the movie to delete.
        :param year: The release year of the movie to delete.
        """
        try:
            self.table.delete_item(Key={'year': year, 'title': title})
        except ClientError as err:
            logger.error(
                "Couldn't delete movie %s. Here's why: %s: %s", title,
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise

    def delete_table(self):
        """
        Deletes the table.
        """
        try:
            self.table.delete()
            self.table = None
        except ClientError as err:
            logger.error(
                "Couldn't delete table. Here's why: %s: %s",
                err.response['Error']['Code'], err.response['Error']['Message'])
            raise

创建帮助函数以下载并提取示例 JSON 文件。

def get_sample_movie_data(movie_file_name):
    """
    Gets sample movie data, either from a local file or by first downloading it from
    the Amazon DynamoDB developer guide.

    :param movie_file_name: The local file name where the movie data is stored in JSON format.
    :return: The movie data as a dict.
    """
    if not os.path.isfile(movie_file_name):
        print(f"Downloading {movie_file_name}...")
        movie_content = requests.get(
            'https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/samples/moviedata.zip')
        movie_zip = ZipFile(BytesIO(movie_content.content))
        movie_zip.extractall()

    try:
        with open(movie_file_name) as movie_file:
            movie_data = json.load(movie_file, parse_float=Decimal)
    except FileNotFoundError:
        print(f"File {movie_file_name} not found. You must first download the file to "
              "run this demo. See the README for instructions.")
        raise
    else:
        # The sample file lists over 4000 movies, return only the first 250.
        return movie_data[:250]

运行交互式场景以创建表并对其执行操作。

def run_scenario(table_name, movie_file_name, dyn_resource):
    logging.basicConfig(level=logging.INFO, format='%(levelname)s: %(message)s')

    print('-'*88)
    print("Welcome to the Amazon DynamoDB getting started demo.")
    print('-'*88)

    movies = Movies(dyn_resource)
    movies_exists = movies.exists(table_name)
    if not movies_exists:
        print(f"\nCreating table {table_name}...")
        movies.create_table(table_name)
        print(f"\nCreated table {movies.table.name}.")

    my_movie = Question.ask_questions([
        Question('title', "Enter the title of a movie you want to add to the table: "),
        Question('year', "What year was it released? ", Question.is_int),
        Question(
            'rating', "On a scale of 1 - 10, how do you rate it? ",
            Question.is_float, Question.in_range(1, 10)),
        Question('plot', "Summarize the plot for me: ")
    ])
    movies.add_movie(**my_movie)
    print(f"\nAdded '{my_movie['title']}' to '{movies.table.name}'.")
    print('-'*88)

    movie_update = Question.ask_questions([
        Question(
            'rating',
            f"\nLet's update your movie.\nYou rated it {my_movie['rating']}, what new "
            f"rating would you give it? ", Question.is_float, Question.in_range(1, 10)),
        Question(
            'plot',
            f"You summarized the plot as '{my_movie['plot']}'.\nWhat would you say now? ")])
    my_movie.update(movie_update)
    updated = movies.update_movie(**my_movie)
    print(f"\nUpdated '{my_movie['title']}' with new attributes:")
    pprint(updated)
    print('-'*88)

    if not movies_exists:
        movie_data = get_sample_movie_data(movie_file_name)
        print(f"\nReading data from '{movie_file_name}' into your table.")
        movies.write_batch(movie_data)
        print(f"\nWrote {len(movie_data)} movies into {movies.table.name}.")
    print('-'*88)

    title = "The Lord of the Rings: The Fellowship of the Ring"
    if Question.ask_question(
            f"Let's move on...do you want to get info about '{title}'? (y/n) ",
            Question.is_yesno):
        movie = movies.get_movie(title, 2001)
        print("\nHere's what I found:")
        pprint(movie)
    print('-'*88)

    ask_for_year = True
    while ask_for_year:
        release_year = Question.ask_question(
            f"\nLet's get a list of movies released in a given year. Enter a year between "
            f"1972 and 2018: ", Question.is_int, Question.in_range(1972, 2018))
        releases = movies.query_movies(release_year)
        if releases:
            print(f"There were {len(releases)} movies released in {release_year}:")
            for release in releases:
                print(f"\t{release['title']}")
            ask_for_year = False
        else:
            print(f"I don't know about any movies released in {release_year}!")
            ask_for_year = Question.ask_question("Try another year? (y/n) ", Question.is_yesno)
    print('-'*88)

    years = Question.ask_questions([
        Question(
            'first',
            f"\nNow let's scan for movies released in a range of years. Enter a year: ",
            Question.is_int, Question.in_range(1972, 2018)),
        Question(
            'second', "Now enter another year: ",
            Question.is_int, Question.in_range(1972, 2018))])
    releases = movies.scan_movies(years)
    if releases:
        count = Question.ask_question(
            f"\nFound {len(releases)} movies. How many do you want to see? ",
            Question.is_int, Question.in_range(1, len(releases)))
        print(f"\nHere are your {count} movies:\n")
        pprint(releases[:count])
    else:
        print(f"I don't know about any movies released between {years['first']} "
              f"and {years['second']}.")
    print('-'*88)

    if Question.ask_question(
            f"\nLet's remove your movie from the table. Do you want to remove "
            f"'{my_movie['title']}'? (y/n)", Question.is_yesno):
        movies.delete_movie(my_movie['title'], my_movie['year'])
        print(f"\nRemoved '{my_movie['title']}' from the table.")
    print('-'*88)

    if Question.ask_question(f"\nDelete the table? (y/n) ", Question.is_yesno):
        movies.delete_table()
        print(f"Deleted {table_name}.")
    else:
        print("Don't forget to delete the table when you're done or you might incur "
              "charges on your account.")

    print("\nThanks for watching!")
    print('-'*88)


if __name__ == '__main__':
    try:
        run_scenario(
            'doc-example-table-movies', 'moviedata.json', boto3.resource('dynamodb'))
    except Exception as e:
        print(f"Something went wrong with the demo! Here's what: {e}")

此场景使用以下帮助程序类在命令提示符处提问。

class Question:
    """
    A helper class to ask questions at a command prompt and validate and convert
    the answers.
    """
    def __init__(self, key, question, *validators):
        """
        :param key: The key that is used for storing the answer in a dict, when
                    multiple questions are asked in a set.
        :param question: The question to ask.
        :param validators: The answer is passed through the list of validators until
                           one fails or they all pass. Validators may also convert the
                           answer to another form, such as from a str to an int.
        """
        self.key = key
        self.question = question
        self.validators = Question.non_empty, *validators

    @staticmethod
    def ask_questions(questions):
        """
        Asks a set of questions and stores the answers in a dict.

        :param questions: The list of questions to ask.
        :return: A dict of answers.
        """
        answers = {}
        for question in questions:
            answers[question.key] = Question.ask_question(
                question.question, *question.validators)
        return answers

    @staticmethod
    def ask_question(question, *validators):
        """
        Asks a single question and validates it against a list of validators.
        When an answer fails validation, the complaint is printed and the question
        is asked again.

        :param question: The question to ask.
        :param validators: The list of validators that the answer must pass.
        :return: The answer, converted to its final form by the validators.
        """
        answer = None
        while answer is None:
            answer = input(question)
            for validator in validators:
                answer, complaint = validator(answer)
                if answer is None:
                    print(complaint)
                    break
        return answer

    @staticmethod
    def non_empty(answer):
        """
        Validates that the answer is not empty.
        :return: The non-empty answer, or None.
        """
        return answer if answer != '' else None, "I need an answer. Please?"

    @staticmethod
    def is_yesno(answer):
        """
        Validates a yes/no answer.
        :return: True when the answer is 'y'; otherwise, False.
        """
        return answer.lower() == 'y', ""

    @staticmethod
    def is_int(answer):
        """
        Validates that the answer can be converted to an int.
        :return: The int answer; otherwise, None.
        """
        try:
            int_answer = int(answer)
        except ValueError:
            int_answer = None
        return int_answer, f"{answer} must be a valid integer."

    @staticmethod
    def is_letter(answer):
        """
        Validates that the answer is a letter.
        :return The letter answer, converted to uppercase; otherwise, None.
        """
        return answer.upper() if answer.isalpha() else None, f"{answer} must be a single letter."

    @staticmethod
    def is_float(answer):
        """
        Validate that the answer can be converted to a float.
        :return The float answer; otherwise, None.
        """
        try:
            float_answer = float(answer)
        except ValueError:
            float_answer = None
        return float_answer, f"{answer} must be a valid float."

    @staticmethod
    def in_range(lower, upper):
        """
        Validate that the answer is within a range. The answer must be of a type that can
        be compared to the lower and upper bounds.
        :return: The answer, if it is within the range; otherwise, None.
        """
        def _validate(answer):
            return (
                answer if lower <= answer <= upper else None,
                f"{answer} must be between {lower} and {upper}.")
        return _validate

创建封装 DynamoDB 表的类。

require "aws-sdk-dynamodb"
require "json"
require "open-uri"
require "pp"
require "zip"
require_relative "question"

# Encapsulates an Amazon DynamoDB table of movie data.
class Movies
  attr_reader :dynamo_resource
  attr_reader :table

  def initialize(dynamo_resource)
    @dynamo_resource = dynamo_resource
  end

  # Determines whether a table exists. As a side effect, stores the table in
  # a member variable.
  #
  # @param table_name [String] The name of the table to check.
  # @return [Boolean] True when the table exists; otherwise, False.
  def exists?(table_name)
    table = Aws::DynamoDB::Table.new(table_name)
    table.load
    @table = table
  rescue Aws::DynamoDB::Errors::ResourceNotFoundException
    puts("Table #{table_name} doesn't exist. Let's create it.")
    false
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't check for existence of #{table_name}. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  else
    !@table.nil?
  end

  # Creates an Amazon DynamoDB table that can be used to store movie data.
  # The table uses the release year of the movie as the partition key and the
  # title as the sort key.
  #
  # @param table_name [String] The name of the table to create.
  # @return [Aws::DynamoDB::Table] The newly created table.
  def create_table(table_name)
    @table = @dynamo_resource.create_table(
      table_name: table_name,
      key_schema: [
        {attribute_name: "year", key_type: "HASH"},  # Partition key
        {attribute_name: "title", key_type: "RANGE"}  # Sort key
      ],
      attribute_definitions: [
        {attribute_name: "year", attribute_type: "N"},
        {attribute_name: "title", attribute_type: "S"}
      ],
      provisioned_throughput: {read_capacity_units: 10, write_capacity_units: 10})
    @dynamo_resource.client.wait_until(:table_exists, table_name: table_name)
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't create table #{table_name}. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  else
    @table
  end

  # Fills an Amazon DynamoDB table with the specified data. Items are sent in
  # batches of 25 until all items are written.
  #
  # @param movies [Enumerable] The data to put in the table. Each item must contain at least
  #                            the keys required by the schema that was specified when the
  #                            table was created.
  def write_batch(movies)
    index = 0
    slice_size = 25
    while index < movies.length
      movie_items = []
      movies[index, slice_size].each do |movie|
        movie_items.append({put_request: { item: movie }})
      end
      @dynamo_resource.batch_write_item({request_items: { @table.name => movie_items }})
      index += slice_size
    end
  rescue Aws::Errors::ServiceError => e
    puts(
      "Couldn't load data into table #{@table.name}. Here's why:")
      puts("\t#{e.code}: #{e.message}")
    raise
  end

  # Adds a movie to the table.
  #
  # @param title [String] The title of the movie.
  # @param year [Integer] The release year of the movie.
  # @param plot [String] The plot summary of the movie.
  # @param rating [Float] The quality rating of the movie.
  def add_movie(title:, year:, plot:, rating:)
    @table.put_item(
      item: {
        "year" => year,
        "title" => title,
        "info" => {"plot" => plot, "rating" => rating}})
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't add movie #{title} to table #{@table.name}. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  end

  # Gets movie data from the table for a specific movie.
  #
  # @param title [String] The title of the movie.
  # @param year [Integer] The release year of the movie.
  # @return [Hash] The data about the requested movie.
  def get_movie(title, year)
    response = @table.get_item(key: {"year" => year, "title" => title})
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't get movie #{title} from table #{@table.name}. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  else
    response.item
  end

  # Updates rating and plot data for a movie in the table.
  #
  # @param title [String] The title of the movie to update.
  # @param year [Int] The release year of the movie to update.
  # @param rating [Float] The updated rating to give the movie.
  # @param plot [String] The updated plot summary to give the movie.
  # @return [Hash] The fields that were updated, with their new values.
  def update_movie(title:, year:, rating:, plot:)
    response = @table.update_item(
      key: {"year" => year, "title" => title},
      update_expression: "set info.rating=:r, info.plot=:p",
      expression_attribute_values: { ":r" => rating, ":p" => plot },
      return_values: "UPDATED_NEW")
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't update movie #{title} in table #{@table.name}. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  else
    response.attributes
  end

  # Queries for movies that were released in the specified year.
  #
  # @param year [Integer] The year to query.
  # @return [Array] The list of movies that were released in the specified year.
  def query_movies(year)
    response = @table.query(
      key_condition_expression: "#yr = :year",
      expression_attribute_names: {"#yr" => "year"},
      expression_attribute_values: {":year" => year})
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't query for movies released in #{year}. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  else
    response.items
  end

  # Scans for movies that were released in a range of years.
  # Uses a projection expression to return a subset of data for each movie.
  #
  # @param year_range [Hash] The range of years to retrieve.
  # @return [Array] The list of movies released in the specified years.
  def scan_movies(year_range)
    movies = []
    scan_hash = {
      filter_expression: "#yr between :start_yr and :end_yr",
      projection_expression: "#yr, title, info.rating",
      expression_attribute_names: {"#yr" => "year"},
      expression_attribute_values: {
        ":start_yr" => year_range[:start], ":end_yr" => year_range[:end]}
    }
    done = false
    start_key = nil
    until done
      scan_hash[:exclusive_start_key] = start_key unless start_key.nil?
      response = @table.scan(scan_hash)
      movies.concat(response.items) unless response.items.nil?
      start_key = response.last_evaluated_key
      done = start_key.nil?
    end
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't scan for movies. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  else
    movies
  end

  # Deletes a movie from the table.
  #
  # @param title [String] The title of the movie to delete.
  # @param year [Integer] The release year of the movie to delete.
  def delete_movie(title, year)
    @table.delete_item(key: {"year" => year, "title" => title})
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't delete movie #{title}. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  end

  # Deletes the table.
  def delete_table
    @table.delete
    @table = nil
  rescue Aws::Errors::ServiceError => e
    puts("Couldn't delete table. Here's why:")
    puts("\t#{e.code}: #{e.message}")
    raise
  end
end

创建帮助函数以下载并提取示例 JSON 文件。

# Gets sample movie data, either from a local file or by first downloading it from
# the Amazon DynamoDB Developer Guide.
#
# @param movie_file_name [String] The local file name where the movie data is stored in JSON format.
# @return [Hash] The movie data as a Hash.
def get_sample_movie_data(movie_file_name)
  if !File.file?(movie_file_name)
    puts("Downloading #{movie_file_name}...")
    movie_content = URI.open(
      "https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/samples/moviedata.zip"
    )
    movie_json = ""
    Zip::File.open_buffer(movie_content) do |zip|
      zip.each do |entry|
        movie_json = entry.get_input_stream.read
      end
    end
  else
    movie_json = File.read(movie_file_name)
  end
  movie_data = JSON.parse(movie_json)
  # The sample file lists over 4000 movies. This returns only the first 250.
  movie_data.slice(0, 250)
rescue Errno::ENOENT
  puts("File #{movie_file_name} not found. Before you can run this demo, you must "\
       "download the file. For instructions, see the README.")
  raise
end

运行交互式场景以创建表并对其执行操作。

# Runs the DynamoDB getting started demo.
#
# @param movies [Movies] A wrapper class initialized with a DynamoDB resource.
# @param table_name [String] The name to give the movie table.
# @param movie_file_name [String] The name of a file that contains movie data in JSON
#                                 format. This data is loaded into the movie table
#                                 as part of the demo.
def run_scenario(movies, table_name, movie_file_name)
  puts("-" * 88)
  puts("Welcome to the DynamoDB getting started demo.")
  puts("-" * 88)

  movies_exists = movies.exists?(table_name)
  unless movies_exists
    puts("\nCreating table #{table_name}...")
    movies.create_table(table_name)
    puts("\nCreated table #{movies.table.name}.")
  end

  my_movie = {}
  my_movie[:title] = Question.ask("Enter the title of a movie to add to the table: ")
  my_movie[:year] = Question.ask("What year was it released? ", method(:is_int))
  my_movie[:rating] = Question.ask(
    "On a scale of 1 - 10, how do you rate it? ", method(:is_float), in_range(1, 10)
  )
  my_movie[:plot] = Question.ask("Summarize the plot for me: ")

  movies.add_movie(**my_movie)
  puts("\nAdded '#{my_movie[:title]}' to '#{movies.table.name}'.")
  puts("-" * 88)

  puts("Let's update your movie. You rated it #{my_movie[:rating]}.")
  my_movie[:rating] = Question.ask("What new rating would you give it? ",
    method(:is_float), in_range(1, 10))
  puts("You summarized the plot as '#{my_movie[:plot]}'.")
  my_movie[:plot] = Question.ask("What would you say now? ")
  updated = movies.update_movie(**my_movie)
  puts("Updated '#{my_movie[:title]}' with new attributes:")
  pp(updated)
  puts("-" * 88)

  unless movies_exists
    movie_data = get_sample_movie_data(movie_file_name)
    puts("Reading data from '#{movie_file_name}' into your table.")
    movies.write_batch(movie_data)
    puts("Wrote #{movie_data.length} movies into #{movies.table.name}.")
    puts("-" * 88)
  end

  title = "The Lord of the Rings: The Fellowship of the Ring"
  if Question.ask("Let's move on. Do you want to get info about '#{title}'? (y/n) ",
         method(:is_yesno))
    movie = movies.get_movie(title, 2001)
    puts("\nHere's what I found:")
    pp(movie)
    puts("-" * 88)
  end

  ask_for_year = true
  puts("Let's get a list of movies released in a given year.")
  while ask_for_year
    release_year = Question.ask(
      "Enter a year between 1972 and 2018: ", method(:is_int), in_range(1972, 2018))
    releases = movies.query_movies(release_year)
    if !releases.empty?
      puts("There were #{releases.length} movies released in #{release_year}:")
      releases.each do |release|
        puts("\t#{release["title"]}")
        ask_for_year = false
      end
    else
      puts("I don't know about any movies released in #{release_year}!")
      ask_for_year = Question.ask("Try another year? (y/n) ", method(:is_yesno))
      puts("-" * 88)
    end
  end

  years = {}
  years[:start] = Question.ask(
    "Let's scan for movies released in a range of years. Enter a year: ",
    method(:is_int), in_range(1972, 2018))
  years[:end] = Question.ask(
    "Now enter another year: ", method(:is_int), in_range(1972, 2018))
  releases = movies.scan_movies(years)
  if !releases.empty?
    puts("Found #{releases.length} movies.")
    count = Question.ask(
      "How many do you want to see? ", method(:is_int), in_range(1, releases.length))
    puts("Here are your #{count} movies:")
    releases.take(count).each do |release|
      puts("\t#{release["title"]}")
    end
  else
    puts("I don't know about any movies released between #{years[:start]} "\
         "and #{years[:end]}.")
  puts("-" * 88)
  end

  puts("Let's remove your movie from the table.")
  if Question.ask(
    "Do you want to remove '#{my_movie[:title]}'? (y/n) ", method(:is_yesno))
    movies.delete_movie(my_movie[:title], my_movie[:year])
    puts("Removed '#{my_movie[:title]}' from the table.")
    puts("-" * 88)
  end

  if Question.ask("Delete the table? (y/n) ", method(:is_yesno))
    movies.delete_table
    puts("Deleted #{table_name}.")
  else
    puts("Don't forget to delete the table when you're done or you might incur "\
      "charges on your account.")
  end

  puts("\nThanks for watching!")
  puts("-" * 88)
rescue Aws::Errors::ServiceError
  puts("Something went wrong with the demo.")
rescue Errno::ENOENT
  true
end

run_scenario(
  Movies.new(Aws::DynamoDB::Resource.new),
"doc-example-table-movies", "moviedata.json",
  ) if $PROGRAM_NAME == __FILE__

此场景使用以下帮助程序类在命令提示符处提问。

# Asks a single question and validates it against a list of validators.
# When an answer fails validation, the complaint is printed and the question
# is asked again.
#
# @param question [String] The question to ask.
# @param validators [Array] The list of validators that the answer must pass.
# @return The answer, converted to its final form by the validators.
class Question
  def self.ask(question, *validators)
    answer = nil
    while answer.nil?
      puts(question)
      answer = gets.chomp
      validators.unshift(method(:non_empty)) unless validators[0] == method(:non_empty)
      validators.each do |validator|
        answer, complaint = validator.call(answer)
        if answer.nil?
          puts(complaint)
          break
        end
      end
    end
    answer
  end
end

# Validates that the answer is not empty.
# @return [Array] The non-empty answer, or nil.
def non_empty(answer)
  answer = nil unless answer != ""
  [answer, "I need an answer. Please?"]
end

# Validates a yes/no answer.
# @return [Array] True when the answer is 'y'; otherwise, False.
def is_yesno(answer)
  [answer.downcase == "y", ""]
end

# Validates that the answer can be converted to an int.
# @return [Array] The int answer; otherwise, nil.
def is_int(answer)
  int_answer = answer.to_i
  if int_answer == 0
    int_answer = nil
  end
  [int_answer, "#{answer} must be a valid integer."]
end

# Validates that the answer can be converted to a float.
# :return [Array] The float answer; otherwise, None.
def is_float(answer)
  float_answer = answer.to_f
  if float_answer == 0.0
    float_answer = nil
  end
  [float_answer, "#{answer} must be a valid float."]
end

# Validates that the answer is within a range. The answer must be of a type that can
# be compared to the lower and upper bounds.
# @return [Proc] A Proc that can be called to determine whether the answer is within
#                the expected range.
def in_range(lower, upper)
  Proc.new { |answer|
    answer.between?(lower, upper) ? range_answer = answer : range_answer = nil
    [range_answer, "#{answer} must be between #{lower} and #{upper}."]
  }
end