Query Hash Key Only in DynamoDB Using Java (Guide w/ Code Examples)

In DynamoDB, a query operation allows you to retrieve items from a table based on their primary key values. The primary key is composed of one or two attributes, a partition key (also known as a "hash key"), and an optional sort key (also known as a "range key").

Querying a table using only the partition key is called a "query by hash key" operation. In Java, you can use the DynamoDBMapper class to perform a query by hash key, by creating a DynamoDBQueryExpression object and specifying the partition key value.

import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBQueryExpression;

public class QueryHashKeyExample {

    public static void main(String[] args) {
        // Create a new DynamoDBMapper
        AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard().build();
        DynamoDBMapper mapper = new DynamoDBMapper(client);

        // Define the hash key value to query
        String hashKeyValue = "123";

        // Define the query expression
        DynamoDBQueryExpression<Product> queryExpression = new DynamoDBQueryExpression<Product>()
            .withHashKeyValues(new Product(hashKeyValue))
            .withConsistentRead(false);

        // Perform the query
        List<Product> items = mapper.query(Product.class, queryExpression);

        // Print the query results
        for (Product item : items) {
            System.out.println(item);
        }
    }
}