为什么 Apache CloseableHttpResponse 在关闭时不使用实体? [英] Why does Apache CloseableHttpResponse not consume the entity on close?

问题描述

查看快速入门指南 它给出了以下代码示例:

Looking at the quick start guide it gives the following code example:

CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpGet = new HttpGet("http://targethost/homepage");
CloseableHttpResponse response1 = httpclient.execute(httpGet);
// The underlying HTTP connection is still held by the response object
// to allow the response content to be streamed directly from the network socket.
// In order to ensure correct deallocation of system resources
// the user MUST call CloseableHttpResponse#close() from a finally clause.
// Please note that if response content is not fully consumed the underlying
// connection cannot be safely re-used and will be shut down and discarded
// by the connection manager. 
try {
    System.out.println(response1.getStatusLine());
    HttpEntity entity1 = response1.getEntity();
    // do something useful with the response body
    // and ensure it is fully consumed
    EntityUtils.consume(entity1);
} finally {
    response1.close();
}

上面代码中的两条注释说我们必须为

The two comments in the code above say that we must close the response object for

正确释放系统资源"

和

如果响应内容没有被完全消耗掉，底层连接就不能安全地重用，连接管理器将关闭并丢弃".

"if response content is not fully consumed the underlying connection cannot be safely re-used and will be shut down and discarded by the connection manager".

现在 Apache 非常友好地为我们实现了 CloseableHttpResponse，这意味着我们可以使用 try-with-resources 块.但是close方法只是关闭了响应对象，为什么不也消费实体呢?

Now Apache have very kindly implementend a CloseableHttpResponse for us, which means we can use a try-with-resources block. But the close method only closes the response object, why doesn't it also consume the entity?

推荐答案

因为此时很难说调用者是否打算重用底层连接.在某些情况下，人们可能只想从大型响应正文中读取一小块内容并立即终止连接.

Because it is hard to say at that point whether or not the caller intends to re-use the underlying connection. In some cases one may want to read just a small chunk from a large response body and immediately terminate the connection.

换句话说，同样的事情一遍又一遍地发生:没有一种方法可以让每个人都开心.

In other words, the same thing happens over and over again: there is no one way that can make everyone happy.

该代码片段将确保正确解除资源分配，同时尝试保持底层连接处于活动状态.

The code snippet will do ensure proper de-allocation of resources while trying to keep the underlying connection alive.

CloseableHttpClient httpclient = HttpClients.createDefault();
HttpGet httpGet = new HttpGet("http://targethost/homepage");
CloseableHttpResponse response1 = httpclient.execute(httpGet);
try {
    System.out.println(response1.getStatusLine());
} finally {
    EntityUtils.consume(response1.getEntity());
} 

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