Query Index in DynamoDB Using Java (Guide w/ Code Examples)

You can use the QueryRequest class offered in the DynamoDB SDK to perform a query. You will have to provide a Table Name, Optional Index Name, and a Key Condition Expression. If you've provided an Index Name, DynamoDB will query the index belonging to the table. However, if the index is not found, DynamoDB will throw an error.

The following code example queries the "MyTable" table using the LastNameIndex index for items where the lastName attribute is "Smith". The QueryRequest class is used to specify the index name and the key condition expression, which in this case, is lastName = :val. The expressionAttributeValues map is used to specify the value to be used in the key condition expression, in this case ":val" is mapped to the value Smith.

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.QueryRequest;
import com.amazonaws.services.dynamodbv2.model.QueryResult;

public class QueryIndexExample {

    public static void main(String[] args) {
        AmazonDynamoDB client = AmazonDynamoDBClientBuilder.defaultClient();

        Map<String, AttributeValue> expressionAttributeValues = new HashMap<>();
        expressionAttributeValues.put(":val", new AttributeValue().withS("Smith"));

        QueryRequest queryRequest = new QueryRequest()
                .withTableName("MyTable")
                .withIndexName("LastNameIndex")
                .withKeyConditionExpression("lastName = :val")
                .withExpressionAttributeValues(expressionAttributeValues);

        QueryResult result = client.query(queryRequest);
        result.getItems().forEach(item -> System.out.println(item));
    }
}