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

To delete an item from a DynamoDB table using a delete expression in the AWS SDK for Java, you can use the deleteItem method of the DynamoDB class. This method allows you to specify a DeleteExpression object in the DeleteItemRequest to specify a delete condition for the item.

The following code shows how you could use the deleteItem method with a delete expression to delete an item from a table named "myTable" only if the item has an attribute named "attr" with a value of "foo". If the delete condition is not met, the deleteItem method will return.

import software.amazon.awssdk.services.dynamodb.DynamoDBClient;
import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
import software.amazon.awssdk.services.dynamodb.model.DeleteItemRequest;
import software.amazon.awssdk.services.dynamodb.model.DeleteItemResponse;
import software.amazon.awssdk.services.dynamodb.model.DynamoDBException;
import software.amazon.awssdk.services.dynamodb.model.Key;
import software.amazon.awssdk.services.dynamodb.model.KeySchemaElement;
import software.amazon.awssdk.services.dynamodb.model.KeyType;
import software.amazon.awssdk.services.dynamodb.model.DeleteExpression;

import java.util.HashMap;
import java.util.Map;

public class DeleteExpressionExample {
    public static void main(String[] args) {
        // Create a DynamoDB clientDynamoDBClient client = DynamoDBClient.create();

        // The primary key of the item to deleteKey key = Key.builder()
            .partitionKey(KeySchemaElement.builder()
                .attributeName("id")
                .keyType(KeyType.HASH)
                .build())
            .build();

        // The delete condition for the item
        Map<String, AttributeValue> conditionExpressionAttributeValues = new HashMap<>();
        conditionExpressionAttributeValues.put(":attrValue", AttributeValue.builder().s("foo").build());
        String conditionExpression = "attr = :attrValue";

        // Create a DeleteExpression object to specify the delete conditionDeleteExpression deleteExpression = DeleteExpression.builder()
            .expressionAttributeValues(conditionExpressionAttributeValues)
            .conditionExpression(conditionExpression)
            .build();

        // Create a DeleteItemRequest object to specify the item to delete and the delete conditionDeleteItemRequest deleteItemRequest = DeleteItemRequest.builder()
            .tableName("myTable")
            .key(key)
            .deleteExpression(deleteExpression)
            .build();

        try {
            // Delete the item if the delete condition is metDeleteItemResponse deleteItemResponse = client.deleteItem(deleteItemRequest);
            System.out.println("Successfully deleted item with delete condition: " + conditionExpression);
        } catch (DynamoDBException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
    }
}