Update Expression in DynamoDB Using Java (Guide w/ Code Examples)

This updates the item in the MyTable table with an id attribute of 123 and sets the "rating" attribute to 5. The UpdateItemRequest class is used to specify the update expression, which is set rating = :val. The expressionAttributeValues map is used to specify the value to be used in the update expression. In this case, :val is mapped to the value 5.

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.UpdateItemRequest;
import com.amazonaws.services.dynamodbv2.model.UpdateItemResult;

public class UpdateExpressionExample {

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

        Map<String, AttributeValue> key = new HashMap<>();
        key.put("id", new AttributeValue().withN("123"));

        Map<String, AttributeValue> expressionAttributeValues = new HashMap<>();
        expressionAttributeValues.put(":val", new AttributeValue().withN("5"));

        UpdateItemRequest updateItemRequest = new UpdateItemRequest()
                .withTableName("MyTable")
                .withKey(key)
                .withUpdateExpression("set rating = :val")
                .withExpressionAttributeValues(expressionAttributeValues);

        UpdateItemResult result = client.updateItem(updateItemRequest);
        System.out.println(result);
    }
}