Error in AWS source code?

Question

In our code, we delete a message from a sqs queue and get the deletResponse.

String deleteResponse = sqsClient.deleteMessage(simBridge2ESBUrl, message.getReceiptHandle()).toString();

The message is deleted after this call but deleteResponse is always {}. So we checked the source code and found DeleteMessageResult::toString function does only return {}.

Below is the AWS source code. The toString() and hashCode() functions seem to be weird. Is there error in the source code or am I doing it wrong? Thanks.

/*
 * Copyright 2010-2016 Amazon.com, Inc. or its affiliates. All Rights
 * Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package com.amazonaws.services.sqs.model;

import java.io.Serializable;

/**
 * 
 */
public class DeleteMessageResult implements Serializable, Cloneable {

    /**
     * Returns a string representation of this object; useful for testing and
     * debugging.
     *
     * @return A string representation of this object.
     *
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("{");
        sb.append("}");
        return sb.toString();
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;

        if (obj instanceof DeleteMessageResult == false)
            return false;
        DeleteMessageResult other = (DeleteMessageResult) obj;
        return true;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int hashCode = 1;

        return hashCode;
    }

    @Override
    public DeleteMessageResult clone() {
        try {
            return (DeleteMessageResult) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new IllegalStateException(
                    "Got a CloneNotSupportedException from Object.clone() "
                            + "even though we're Cloneable!", e);
        }
    }
}

Answer 1

From programming perspective toString() is written correctly. Think about what this function does:

A string representation of this object.

Since DeleteMessageResult class has no properties, there is nothing to return. Same applies to hashCode(). Two objects of DeleteMessageResult are always identical, so they have the same hash every time.

That being said, I do think that DeleteMessageResult should contain ResposeMetadata with unique RequestId as show in API reference:

<DeleteMessageResponse>
    <ResponseMetadata>
        <RequestId>
            b5293cb5-d306-4a17-9048-b263635abe42
        </RequestId>
    </ResponseMetadata>
</DeleteMessageResponse>

So, yes, this class could (probably, should) be patched to fully back the SQS API.