Detailed explanation of the example of HttpClient simulating a browser to initiate a request after logging in in java web

package com.artsoft.demo;

import java.io.FileOutputStream; 
 
import org.apache.http.HttpEntity; 
import org.apache.http.HttpResponse; 
import org.apache.http.client.CookieStore; 
import org.apache.http.client.methods.HttpGet; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.apache.http.impl.conn.PoolingClientConnectionManager; 
import org.apache.http.util.EntityUtils; 
 
/** 
 * TODO(用一句话描述该文件的作用) 
 * 
 * @title: HttpClientDemo.java 
 * @author zhangjinshan-ghq 
 * @date 2014-6-11 14:59:04 
 */ 
 
public class HttpClientDemo 
{ 
 
  /** 
   * The main method. 
   * 
   * @param args the arguments 
   * @throws Exception the exception 
   */ 
  public static void main(String[] args) throws Exception 
  { 
    getResoucesByLoginCookies(); 
  } 
 
  /** 
   * 根据登录Cookie获取资源 
   * 一切异常均未处理，需要酌情检查异常 
   * 
   * @throws Exception 
   */ 
  private static void getResoucesByLoginCookies() throws Exception 
  { 
    HttpClientDemo demo = new HttpClientDemo(); 
    String username = "......";// 登录用户 
    String password = "......";// 登录密码 
 
    // 需要提交登录的信息 
    String urlLogin = "http://hx.buscoming.cn/Api/Security/Logon?UserCode=" + username + "&Password=" + password; 
 
    // 登录成功后想要访问的页面 可以是下载资源 需要替换成自己的iteye Blog地址 
    String urlAfter = "http://hx.buscoming.cn/Api/Security/GetLoginAccount";
 
    DefaultHttpClient client = new DefaultHttpClient(new PoolingClientConnectionManager()); 
 
    /** 
     * 第一次请求登录页面 获得cookie 
     * 相当于在登录页面点击登录，此处在URL中 构造参数， 
     * 如果参数列表相当多的话可以使用HttpClient的方式构造参数 
     * 此处不赘述 
     */ 
    HttpPost post = new HttpPost(urlLogin); 
    HttpResponse response = client.execute(post); 
    HttpEntity entity = response.getEntity(); 
    CookieStore cookieStore = client.getCookieStore(); 
    client.setCookieStore(cookieStore); 
 
    /** 
     * 带着登录过的cookie请求下一个页面，可以是需要登录才能下载的url 
     * 此处使用的是iteye的博客首页，如果登录成功，那么首页会显示【欢迎XXXX】 
     * 
     */ 
    HttpGet get = new HttpGet(urlAfter); 
    response = client.execute(get); 
    entity = response.getEntity(); 
 
    /** 
     * 将请求结果放到文件系统中保存为 myindex.html,便于使用浏览器在本地打开 查看结果 
     */ 
 
    String pathName = "d:\\index.html"; 
    writeHTMLtoFile(entity, pathName); 
  } 
 
  /** 
   * Write htmL to file. 
   * 将请求结果以二进制形式放到文件系统中保存为.html文件,便于使用浏览器在本地打开 查看结果 
   * 
   * @param entity the entity 
   * @param pathName the path name 
   * @throws Exception the exception 
   */ 
  public static void writeHTMLtoFile(HttpEntity entity, String pathName) throws Exception 
  { 
 
    byte[] bytes = new byte[(int) entity.getContentLength()]; 
 
    FileOutputStream fos = new FileOutputStream(pathName); 
 
    bytes = EntityUtils.toByteArray(entity); 
 
    fos.write(bytes); 
 
    fos.flush(); 
 
    fos.close(); 
  } 
 
}