# 使用 Amazon SDK 查询 DynamoDB 表中的 TTL 项目
<a name="example_dynamodb_QueryFilteredTTL_section"></a>

以下代码示例演示了如何查询 TTL 项目。

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#### [ Java ]

**适用于 Java 的 SDK 2.x**  
查询对表达式进行了筛选，以使用Amazon SDK for Java 2.x 在 DynamoDB 表中收集 TTL 项目。  

```
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
import software.amazon.awssdk.services.dynamodb.model.DynamoDbException;
import software.amazon.awssdk.services.dynamodb.model.QueryRequest;
import software.amazon.awssdk.services.dynamodb.model.QueryResponse;
import software.amazon.awssdk.services.dynamodb.model.ResourceNotFoundException;

import java.util.Map;
import java.util.Optional;

        final QueryRequest request = QueryRequest.builder()
            .tableName(tableName)
            .keyConditionExpression(KEY_CONDITION_EXPRESSION)
            .filterExpression(FILTER_EXPRESSION)
            .expressionAttributeNames(expressionAttributeNames)
            .expressionAttributeValues(expressionAttributeValues)
            .build();

        try (DynamoDbClient ddb = dynamoDbClient != null
            ? dynamoDbClient
            : DynamoDbClient.builder().region(region).build()) {
            final QueryResponse response = ddb.query(request);
            System.out.println("Query successful. Found " + response.count() + " items that have not expired yet.");

            // Print each item
            response.items().forEach(item -> {
                System.out.println("Item: " + item);
            });

            return 0;
        } catch (ResourceNotFoundException e) {
            System.err.format(TABLE_NOT_FOUND_ERROR, tableName);
            throw e;
        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            throw e;
        }
```
+  有关 API 详细信息，请参阅《Amazon SDK for Java 2.x API Reference》**中的 [Query](https://docs.amazonaws.cn/goto/SdkForJavaV2/dynamodb-2012-08-10/Query)。

------
#### [ JavaScript ]

**SDK for JavaScript（v3）**  
查询对表达式进行了筛选，以使用适用于 JavaScript 的 Amazon SDK 在 DynamoDB 表中收集 TTL 项目。  

```
import { DynamoDBClient, QueryCommand } from "@aws-sdk/client-dynamodb";
import { marshall, unmarshall } from "@aws-sdk/util-dynamodb";

export const queryFiltered = async (tableName, primaryKey, region = 'us-east-1') => {
    const client = new DynamoDBClient({
        region: region,
        endpoint: `https://dynamodb.${region}.amazonaws.com`
    });

    const currentTime = Math.floor(Date.now() / 1000);

    const params = {
        TableName: tableName,
        KeyConditionExpression: "#pk = :pk",
        FilterExpression: "#ea > :ea",
        ExpressionAttributeNames: {
            "#pk": "primaryKey",
            "#ea": "expireAt"
        },
        ExpressionAttributeValues: marshall({
            ":pk": primaryKey,
            ":ea": currentTime
        })
    };

    try {
        const { Items } = await client.send(new QueryCommand(params));
        Items.forEach(item => {
            console.log(unmarshall(item))
        });
        return Items;
    } catch (err) {
        console.error(`Error querying items: ${err}`);
        throw err;
    }
}

// Example usage (commented out for testing)
// queryFiltered('your-table-name', 'your-partition-key-value');
```
+  有关 API 详细信息，请参阅《适用于 JavaScript 的 Amazon SDK API Reference》**中的 [Query](https://docs.amazonaws.cn/AWSJavaScriptSDK/v3/latest/client/dynamodb/command/QueryCommand)。

------
#### [ Python ]

**适用于 Python 的 SDK（Boto3）**  
查询对表达式进行了筛选，以使用适用于 Python (Boto3) 的 Amazon SDK 在 DynamoDB 表中收集 TTL 项目。  

```
from datetime import datetime

import boto3


def query_dynamodb_items(table_name, partition_key):
    """

    :param table_name: Name of the DynamoDB table
    :param partition_key:
    :return:
    """
    try:
        # Initialize a DynamoDB resource
        dynamodb = boto3.resource("dynamodb", region_name="us-east-1")

        # Specify your table
        table = dynamodb.Table(table_name)

        # Get the current time in epoch format
        current_time = int(datetime.now().timestamp())

        # Perform the query operation with a filter expression to exclude expired items
        # response = table.query(
        #    KeyConditionExpression=boto3.dynamodb.conditions.Key('partitionKey').eq(partition_key),
        #    FilterExpression=boto3.dynamodb.conditions.Attr('expireAt').gt(current_time)
        # )
        response = table.query(
            KeyConditionExpression=dynamodb.conditions.Key("partitionKey").eq(partition_key),
            FilterExpression=dynamodb.conditions.Attr("expireAt").gt(current_time),
        )

        # Print the items that are not expired
        for item in response["Items"]:
            print(item)

    except Exception as e:
        print(f"Error querying items: {e}")


# Call the function with your values
query_dynamodb_items("Music", "your-partition-key-value")
```
+  有关 API 详细信息，请参阅《Amazon SDK for Python (Boto3) API Reference》**中的 [Query](https://docs.amazonaws.cn/goto/boto3/dynamodb-2012-08-10/Query)。

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有关 Amazon SDK 开发人员指南和代码示例的完整列表，请参阅 [结合使用 DynamoDB 与 Amazon SDK](sdk-general-information-section.md) 本主题还包括有关入门的信息以及有关先前的 SDK 版本的详细信息。