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
数据缓存
使用HttpClient库,您可以使用代理发送HTTP请求.按照下面给出的步骤&减去;
实例化 HttpHost 类 org.apache.http 包通过将表示代理主机名称的字符串参数(从中需要发送请求)传递给其构造函数.
//Creating an HttpHost object for proxy HttpHost proxyHost = new HttpHost("localhost");
以同样的方式,创建另一个HttpHost对象来表示需要发送请求的目标主机.
//Creating an HttpHost object for target HttpHost targetHost = new HttpHost("google.com");
HttpRoutePlanner 接口计算到指定的主机.通过实例化 DefaultProxyRoutePlanner 类来创建此接口的对象,该类是此接口的实现.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);
使用 custom() HttpClients 类的方法,创建一个 HttpClientBuilder 对象,并使用 setRoutePlanner()为此对象设置上面创建的路径规划器方法.
//Setting the route planner to the HttpClientBuilder object HttpClientBuilder clientBuilder = HttpClients.custom(); clientBuilder = clientBuilder.setRoutePlanner(routePlanner);
通过调用构建 CloseableHttpClient 对象 build()方法.
//Building a CloseableHttpClient CloseableHttpClient httpClient = clientBuilder.build();
通过实例化 HttpGet class.
//Creating an HttpGet object HttpGet httpGet = new HttpGet("/");
执行()方法接受 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);
以下示例演示了如何通过代理向服务器发送HTTP请求.在这个
示例中,我们通过localhost向google.com发送HTTP GET请求.我们打印了响应的标题和响应的主体.
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)); } } }
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 <html><body><h1>It works!</h1></body></html>