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

Rafal Wilinski

Provided by Rafal Wilinski

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); } } }

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