java - Apache HttpClient API 中的 CloseableHttpClient 和 HttpClient 有什么区别？

Question

我正在研究我们公司开发的应用程序。它使用 Apache HttpClient 库。在源代码中，它使用 HttpClient 类来创建实例以连接到服务器。

我想了解 Apache HttpClient 并且我已经经历了 this set of examples .所有示例都使用 CloseableHttpClient 而不是 HttpClient。所以我认为CloseableHttpClient 是HttpClient 的扩展版本。如果是这种情况，我有两个问题:

• 这两者有什么区别？
• 建议在我的新开发中使用哪个类？

Answer 1

• HttpClient API 的主要入口点是 HttpClient 接口(interface)。
• HttpClient最基本的功能是执行HTTP方法。
• HTTP 方法的执行涉及一个或多个 HTTP 请求/HTTP 响应交换，通常由 HttpClient 在内部处理。

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• CloseableHttpClient 是一个抽象类，它是 HttpClient 的基础实现，也实现了 java.io.Closeable。

• 以下是最简单形式的请求执行过程示例:

  CloseableHttpClient httpclient = HttpClients.createDefault();
  HttpGet httpget = new HttpGet("http://localhost/");
  CloseableHttpResponse response = httpclient.execute(httpget);
  try {
      //do something
  } finally {
      response.close();
  }

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• HttpClient resource deallocation: When an instance CloseableHttpClient is no longer needed and is about to go out of scope the connection manager associated with it must be shut down by calling the CloseableHttpClient#close() method.

  CloseableHttpClient httpclient = HttpClients.createDefault();
  try {
      //do something
  } finally {
      httpclient.close();
  }

see the Reference to learn fundamentals.

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@Scadge Since Java 7, Use of try-with-resources statement ensures that each resource is closed at the end of the statement. It can be used both for the client and for each response

try(CloseableHttpClient httpclient = HttpClients.createDefault()){

    // e.g. do this many times
    try (CloseableHttpResponse response = httpclient.execute(httpget)) {
    //do something
    }

    //do something else with httpclient here
}