How to query DynamoDB based on Partition Key and Sort Key [Java]?

How to query DynamoDB based on Partition Key and Sort Key [Java]?

To query Amazon DynamoDB based on the Partition Key and Sort Key using Java, you can use the AWS SDK for Java. Here's a simple example using the AWS SDK for DynamoDB:

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 java.util.HashMap; import java.util.Map; public class DynamoDBQueryExample { public static void main(String[] args) { // Replace these values with your AWS credentials and DynamoDB table details String region = "your-region"; String tableName = "your-table-name"; String partitionKey = "your-partition-key-value"; String sortKey = "your-sort-key-value"; // Create a DynamoDB client DynamoDbClient dynamoDbClient = DynamoDbClient.builder() .region(region) .build(); // Create a query request QueryRequest queryRequest = QueryRequest.builder() .tableName(tableName) .keyConditionExpression("#pk = :pk AND #sk = :sk") .expressionAttributeNames(Map.of("#pk", "your-partition-key", "#sk", "your-sort-key")) .expressionAttributeValues(Map.of( ":pk", AttributeValue.builder().s(partitionKey).build(), ":sk", AttributeValue.builder().s(sortKey).build() )) .build(); try { // Execute the query and get the response QueryResponse response = dynamoDbClient.query(queryRequest); // Process the query response (you can iterate through the items in the response) response.items().forEach(item -> System.out.println("Item: " + item)); } catch (DynamoDbException e) { // Handle any exceptions System.err.println("DynamoDB exception: " + e.getMessage()); } finally { // Close the DynamoDB client dynamoDbClient.close(); } } }

Make sure to replace the placeholder values with your actual AWS region, DynamoDB table name, and key values. This example demonstrates a simple query based on the Partition Key and Sort Key values. You can customize the query based on your specific requirements.

Examples

  1. Java DynamoDB Query Using AWS SDK:

    • Description: Learn how to perform a query on DynamoDB using the AWS SDK for Java based on a partition key and sort key.
    • Code:
      AmazonDynamoDB client = AmazonDynamoDBClient.builder().build(); DynamoDbClient dynamoDbClient = DynamoDbClient.builder() .region(Region.US_EAST_1) .build(); DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build())) .build(); PaginatedQueryList<MyItem> results = mapper.query(MyItem.class, queryExpression); for (MyItem item : results) { // Process each item }

  2. Filter DynamoDB Query Results in Java:

    • Description: Add filtering conditions to DynamoDB query results in Java based on partition key and sort key.
    • Code:
      DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .filterExpression("attributeName = :attributeValue") // Add additional filtering conditions .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build()) .put(":attributeValue", AttributeValue.builder().s("desiredValue").build())) .build();

  3. Java DynamoDB Query with Projection Expression:

    • Description: Use projection expressions to specify which attributes to include in DynamoDB query results in Java.
    • Code:
      DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .projectionExpression("attribute1, attribute2") // Specify desired attributes .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build())) .build();

  4. DynamoDB Query with Limit in Java:

    • Description: Limit the number of items returned in a DynamoDB query in Java using the AWS SDK.
    • Code:
      DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build())) .limit(10) // Limit the number of items returned .build();

  5. DynamoDB Query with ScanIndexForward Option in Java:

    • Description: Specify the sort order of DynamoDB query results in Java using the ScanIndexForward option.
    • Code:
      DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build())) .scanIndexForward(false) // Set to false for descending order .build();

  6. DynamoDB Query with ExclusiveStartKey in Java:

    • Description: Use the ExclusiveStartKey option to start a DynamoDB query from a specific key in Java.
    • Code:
      Map<String, AttributeValue> exclusiveStartKey = new HashMap<>(); exclusiveStartKey.put("partitionKey", AttributeValue.builder().s("startPartitionKey").build()); exclusiveStartKey.put("sortKey", AttributeValue.builder().s("startSortKey").build()); DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build())) .exclusiveStartKey(exclusiveStartKey) .build();

  7. DynamoDB Query with ConsistentRead in Java:

    • Description: Enable consistent read in DynamoDB queries in Java to get the most up-to-date results.
    • Code:
      DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build())) .consistentRead(true) // Enable consistent read .build();

  8. Java DynamoDB Query with Filter Expression:

    • Description: Add a filter expression to DynamoDB queries in Java to further filter results after the initial key conditions.
    • Code:
      DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .filterExpression("attributeName = :attributeValue") // Add additional filtering conditions .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build()) .put(":attributeValue", AttributeValue.builder().s("desiredValue").build())) .build();

  9. DynamoDB Query with ProjectionExpression in Java:

    • Description: Use ProjectionExpression to specify which attributes to include in DynamoDB query results in Java.
    • Code:
      DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .projectionExpression("attribute1, attribute2") // Specify desired attributes .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build())) .build();

  10. Java DynamoDB Query with Filter Expression and Limit:

    • Description: Combine filter expression and limit in DynamoDB queries in Java for more controlled and efficient results.
    • Code:
      DynamoDbQueryExpression<MyItem> queryExpression = DynamoDbQueryExpression.builder() .tableName("YourTableName") .keyConditionExpression("partitionKey = :partitionKey and sortKey = :sortKey") .filterExpression("attributeName = :attributeValue") // Add additional filtering conditions .expressionAttributeValues(Collections.singletonMap(":partitionKey", AttributeValue.builder().s("yourPartitionKeyValue").build()) .put(":sortKey", AttributeValue.builder().s("yourSortKeyValue").build()) .put(":attributeValue", AttributeValue.builder().s("desiredValue").build())) .limit(10) // Limit the number of items returned .build();

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