HttpClient设置代理

在做爬虫抓取网站数据时，通常可能会遇到一个问题，那就是服务器对访问IP做了一定的限制，比如限制单位时间内的访问次数等。这个时候，我们可以使用代理的方式进行解决。

我们可以使用HttpClient提供的方式进行代理设置，官方给出的代码示例如下：

[code]package org.apache.http.examples.client;

import org.apache.http.HttpHost;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

/**
 * How to send a request via proxy.
 *
 * @since 4.0
 */
public class ClientExecuteProxy {

    public static void main(String[] args)throws Exception {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        try {
            HttpHost target = new HttpHost("localhost", 443, "https");  //这个是目标主机，即您要访问的服务器，比较网站。
            HttpHost proxy = new HttpHost("127.0.0.1", 8080, "http");  //这个是代理信息，即我们要通过哪个代理主机进行代理请求访问。

            RequestConfig config = RequestConfig.custom()
                    .setProxy(proxy)
                    .build();
            HttpGet request = new HttpGet("/");
            request.setConfig(config);

            System.out.println("Executing request " + request.getRequestLine() + " to " + target + " via " + proxy);

            CloseableHttpResponse response = httpclient.execute(target, request);  //执行请求。
            try {
                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());  //打印状态信息
                EntityUtils.consume(response.getEntity());
            } finally {
                response.close();
            }
        } finally {
            httpclient.close();
        }
    }

}