java - AWS 源代码错误？

Question

在我们的代码中，我们从 sqs 队列中删除一条消息并获取 deletResponse。

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

此调用后消息被删除，但 deleteResponse 始终为 {}。所以我们检查了源代码，发现 DeleteMessageResult::toString 函数只返回 {}。

以下是 AWS 源代码。 toString() 和hashCode() 函数看起来很奇怪。源代码有错误还是我做错了？谢谢。

/*
 * 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

从编程的角度来看，toString() 是正确编写的。想想这个函数做了什么:

A string representation of this object.

因为 DeleteMessageResult 类没有属性，所以没有什么可以返回的。这同样适用于 hashCode()。 DeleteMessageResult 的两个对象始终相同，因此它们每次都具有相同的哈希值。

话虽如此，我确实认为 DeleteMessageResult 应该包含具有唯一 RequestId 的 ResposeMetadata，如 API reference 中所示:

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

所以，是的，这个类可以(可能，应该)被修补以完全支持 SQS API。