Amazon DynamoDB
开发人员指南 (API 版本 2012-08-10)
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向 DynamoDB (使用适用于 .NET 的 AWS 开发工具包对象持久化模型) 映射任意数据

除支持的 .NET 类型(请参阅受支持数据类型)外,您还可以在应用程序中使用不能直接映射到 DynamoDB 的类型。只要您提供的转换器可数据由任意类型转换为 DynamoDB 类型 (反之亦然),对象持久化模型就支持存储任意类型的数据。转换器代码会在保存和加载数据元期间转换数据。

您可以在客户端创建任意类型,但是,表中存储的数据属于某种 DynamoDB 类型,并且在查询和扫描期间,所有数据比较都是针对 DynamoDB 中存储的数据进行。

以下 C# 代码示例定义包含 BookIdTitleISBN 属性的 Dimension 类。Dimension 属性属于描述 DimensionTypeHeightWidth 属性的 Thickness。该示例代码提供转换器方法(ToEntryFromEntry)在 DimensionType 和 DynamoDB 字符串类型之间转换数据。例如,在保存 Book 实例时,转换器会创建图书 Dimension 字符串 (例如 8.5x11x.05),并且在您检索某一图书时,它还会将该字符串转换为 DimensionType 实例。

该示例将 Book 类型映射到 ProductCatalog 表。为说明起见,它会保存 Book 实例示例、对其进行检索,更新其尺寸以及重新保存更新过的 Book

有关如何测试以下示例的分步说明,请参阅.NET 代码示例

using System; using System.Collections.Generic; using Amazon.DynamoDBv2; using Amazon.DynamoDBv2.DataModel; using Amazon.DynamoDBv2.DocumentModel; using Amazon.Runtime; using Amazon.SecurityToken; namespace com.amazonaws.codesamples { class HighLevelMappingArbitraryData { private static AmazonDynamoDBClient client = new AmazonDynamoDBClient(); static void Main(string[] args) { try { DynamoDBContext context = new DynamoDBContext(client); // 1. Create a book. DimensionType myBookDimensions = new DimensionType() { Length = 8M, Height = 11M, Thickness = 0.5M }; Book myBook = new Book { Id = 501, Title = "AWS SDK for .NET Object Persistence Model Handling Arbitrary Data", ISBN = "999-9999999999", BookAuthors = new List<string> { "Author 1", "Author 2" }, Dimensions = myBookDimensions }; context.Save(myBook); // 2. Retrieve the book. Book bookRetrieved = context.Load<Book>(501); // 3. Update property (book dimensions). bookRetrieved.Dimensions.Height += 1; bookRetrieved.Dimensions.Length += 1; bookRetrieved.Dimensions.Thickness += 0.2M; // Update the book. context.Save(bookRetrieved); Console.WriteLine("To continue, press Enter"); Console.ReadLine(); } catch (AmazonDynamoDBException e) { Console.WriteLine(e.Message); } catch (AmazonServiceException e) { Console.WriteLine(e.Message); } catch (Exception e) { Console.WriteLine(e.Message); } } } [DynamoDBTable("ProductCatalog")] public class Book { [DynamoDBHashKey] //Partition key public int Id { get; set; } [DynamoDBProperty] public string Title { get; set; } [DynamoDBProperty] public string ISBN { get; set; } // Multi-valued (set type) attribute. [DynamoDBProperty("Authors")] public List<string> BookAuthors { get; set; } // Arbitrary type, with a converter to map it to DynamoDB type. [DynamoDBProperty(typeof(DimensionTypeConverter))] public DimensionType Dimensions { get; set; } } public class DimensionType { public decimal Length { get; set; } public decimal Height { get; set; } public decimal Thickness { get; set; } } // Converts the complex type DimensionType to string and vice-versa. public class DimensionTypeConverter : IPropertyConverter { public DynamoDBEntry ToEntry(object value) { DimensionType bookDimensions = value as DimensionType; if (bookDimensions == null) throw new ArgumentOutOfRangeException(); string data = string.Format("{1}{0}{2}{0}{3}", " x ", bookDimensions.Length, bookDimensions.Height, bookDimensions.Thickness); DynamoDBEntry entry = new Primitive { Value = data }; return entry; } public object FromEntry(DynamoDBEntry entry) { Primitive primitive = entry as Primitive; if (primitive == null || !(primitive.Value is String) || string.IsNullOrEmpty((string)primitive.Value)) throw new ArgumentOutOfRangeException(); string[] data = ((string)(primitive.Value)).Split(new string[] { " x " }, StringSplitOptions.None); if (data.Length != 3) throw new ArgumentOutOfRangeException(); DimensionType complexData = new DimensionType { Length = Convert.ToDecimal(data[0]), Height = Convert.ToDecimal(data[1]), Thickness = Convert.ToDecimal(data[2]) }; return complexData; } } }