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📜  Apache HttpClient-使用代理

📅  最后修改于: 2020-11-18 08:29:35             🧑  作者: Mango

代理服务器是客户端和Internet之间的中间服务器。代理服务器提供以下基本功能-

  • 防火墙和网络数据过滤

  • 网络连接共享

  • 资料快取

使用HttpClient库，您可以使用代理发送HTTP请求。请按照下面给出的步骤-

第1步-创建HttpHost对象

通过将代表代理主机名(您需要从中发送请求)的字符串参数传递给其构造函数，实例化org.apache.http包的HttpHost类。

//Creating an HttpHost object for proxy
HttpHost proxyHost = new HttpHost("localhost");

以相同的方式，创建另一个HttpHost对象，以表示需要将请求发送到的目标主机。

//Creating an HttpHost object for target
HttpHost targetHost = new HttpHost("google.com");

第2步-创建HttpRoutePlanner对象

HttpRoutePlanner接口计算到指定主机的路由。通过实例化DefaultProxyRoutePlanner类(此接口的实现)来创建此接口的对象。作为其构造函数的参数，传递上面创建的代理主机-

//creating a RoutePlanner object
HttpRoutePlanner routePlanner = new DefaultProxyRoutePlanner(proxyhost);

步骤3-将路线规划器设置为客户端构建器

使用HttpClients类的custom()方法，创建一个HttpClientBuilder对象，并使用setRoutePlanner()方法为此对象设置上面创建的路由计划器。

//Setting the route planner to the HttpClientBuilder object
HttpClientBuilder clientBuilder = HttpClients.custom();

clientBuilder = clientBuilder.setRoutePlanner(routePlanner);

步骤4-构建CloseableHttpClient对象

通过调用build()方法来构建CloseableHttpClient对象。

//Building a CloseableHttpClient
CloseableHttpClient httpClient = clientBuilder.build();

第5步-创建一个HttpGetobject

通过实例化HttpGet类创建一个HTTP GET请求。

//Creating an HttpGet object
HttpGet httpGet = new HttpGet("/");

第6步-执行请求

execute()方法的变体之一接受HttpHost和HttpRequest对象并执行请求。使用此方法执行请求-

//Executing the Get request
HttpResponse httpResponse = httpclient.execute(targetHost, httpGet);

例

下面的示例演示如何通过代理向服务器发送HTTP请求。在此示例中，我们通过本地主机向google.com发送HTTP GET请求。我们已经打印了响应的标题和响应的正文。

import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.conn.routing.HttpRoutePlanner;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.DefaultProxyRoutePlanner;
import org.apache.http.util.EntityUtils;

public class RequestViaProxyExample {

   public static void main(String args[]) throws Exception{
 
      //Creating an HttpHost object for proxy
      HttpHost proxyhost = new HttpHost("localhost");

      //Creating an HttpHost object for target
      HttpHost targethost = new HttpHost("google.com");
 
      //creating a RoutePlanner object
      HttpRoutePlanner routePlanner = new DefaultProxyRoutePlanner(proxyhost);

      //Setting the route planner to the HttpClientBuilder object
      HttpClientBuilder clientBuilder = HttpClients.custom();
      clientBuilder = clientBuilder.setRoutePlanner(routePlanner);

      //Building a CloseableHttpClient
      CloseableHttpClient httpclient = clientBuilder.build();

      //Creating an HttpGet object
      HttpGet httpget = new HttpGet("/");

      //Executing the Get request
      HttpResponse httpresponse = httpclient.execute(targethost, httpget);

      //Printing the status line
      System.out.println(httpresponse.getStatusLine());

      //Printing all the headers of the response
      Header[] headers = httpresponse.getAllHeaders();
 
      for (int i = 0; i < headers.length; i++) {
         System.out.println(headers[i]);
      }
      
      //Printing the body of the response
      HttpEntity entity = httpresponse.getEntity();

      if (entity != null) {
         System.out.println(EntityUtils.toString(entity));
      }
   }
}

输出

在执行时，以上程序生成以下输出-

HTTP/1.1 200 OK
Date: Sun, 23 Dec 2018 10:21:47 GMT
Server: Apache/2.4.9 (Win64) PHP/5.5.13
Last-Modified: Tue, 24 Jun 2014 10:46:24 GMT
ETag: "2e-4fc92abc3c000"
Accept-Ranges: bytes
Content-Length: 46
Content-Type: text/html

It works!