HttpClient模拟登陆

     HTTP协议本来是无状态的，但为了保持会话的状态，使用COOKIE保存Session信息，当向服务器发送请求时会附加一些会话信息，从而能区分不同会话的状态。用户登陆过程，其实简单而言，就是首先验证用户名与密码，然后服务器生成会话信息保存到本地，最后用户凭借会话信息能够访问类似用户信息等需登陆的网页。

    HttpClient4.5通过COOKIEStore保存用户的会话信息，还提供HttpClientContext保存用户连接的信息。下面是一个使用HttpClient模拟知乎登陆的简单案例。

import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
 
import org.apache.http.Consts;
import org.apache.http.NameValuePair;
import org.apache.http.client.COOKIEStore;
import org.apache.http.client.config.COOKIESpecs;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.COOKIE.COOKIE;
import org.apache.http.impl.client.BasicCOOKIEStore;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
 
/**
 * 模拟登陆知乎
 */
public class ZhiHuTest {
 
  public static void main(String[] args) throws java.text.ParseException {
    String name = "username";
    String password = "password"
     
    // 全局请求设置
    RequestConfig globalCOnfig= RequestConfig.custom().setCOOKIESpec(COOKIESpecs.STANDARD).build();
    // 创建COOKIE store的本地实例
    COOKIEStore COOKIEStore = new BasicCOOKIEStore();
    // 创建HttpClient上下文
    HttpClientContext cOntext= HttpClientContext.create();
    context.setCOOKIEStore(COOKIEStore);
 
    // 创建一个HttpClient
    CloseableHttpClient httpClient = HttpClients.custom().setDefaultRequestConfig(globalConfig)
        .setDefaultCOOKIEStore(COOKIEStore).build();
 
    CloseableHttpResponse res = null;
 
    // 创建本地的HTTP内容
    try {
      try {
        // 创建一个get请求用来获取必要的COOKIE，如_xsrf信息
        HttpGet get = new HttpGet("http://www.zhihu.com/");
 
        res = httpClient.execute(get);
        // 获取常用COOKIE,包括_xsrf信息,放在发送请求之后
        System.out.println("访问知乎首页后的获取的常规COOKIE:===============");
        for (COOKIE c : COOKIEStore.getCOOKIEs()) {
          System.out.println(c.getName() + ": " + c.getValue());
        }
        res.close();
 
        // 构造post数据
        List valuePairs = new LinkedList();
        valuePairs.add(new BasicNameValuePair("email", name));
        valuePairs.add(new BasicNameValuePair("password", password));
        valuePairs.add(new BasicNameValuePair("remember_me", "true"));
        UrlEncodedFormEntity entity = new UrlEncodedFormEntity(valuePairs, Consts.UTF_8);
        entity.setContentType("application/x-www-form-urlencoded");
 
        // 创建一个post请求
        HttpPost post = new HttpPost("https://www.zhihu.com/login/email");
        // 注入post数据
        post.setEntity(entity);
        res = httpClient.execute(post);
 
        // 打印响应信息，查看是否登陆是否成功
        System.out.println("打印响应信息===========");
        HttpClientUtils.printResponse(res);
        res.close();
         
        //放在post请求之后,获取的是响应头的Set-COOKIE 
        System.out.println("登陆成功后,新的COOKIE:===============");
        for (COOKIE c : context.getCOOKIEStore().getCOOKIEs()) {
          System.out.println(c.getName() + ": " + c.getValue());
        }
 
        // 构造一个新的get请求，用来测试登录是否成功
        HttpGet newGet = new HttpGet("http://www.zhihu.com/question/following");
        res = httpClient.execute(newGet, context);
        String cOntent= EntityUtils.toString(res.getEntity());
        System.out.println("登陆成功后访问的页面===============");
        System.out.println(content);
        res.close();
 
      } finally {
        httpClient.close();
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}