最近一直帮老板写爬虫，写累了就寻思着找点乐子，碰巧平时喜欢逛豆瓣，就打算写一个自动回帖机器人，废话不多说我们进入正题:

主要用到2个开源工具：Jsoup和httpclient

Step 1:模拟登陆

public static boolean login() throws IOException{
String captcha_id=downloadPic(login_url,"D:\\yz.png");//下载验证码图片到本地
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("请输入验证码:");
String yan = br.readLine();
HttpPost httppost = new HttpPost(login_url);
List params = new ArrayList();
params.add(new BasicNameValuePair("captcha-id", captcha_id));//用firebug自己找
params.add(new BasicNameValuePair("captcha-solution", yan));//验证码
params.add(new BasicNameValuePair("form_email", form_email));//用户名
params.add(new BasicNameValuePair("form_password", form_password));//密码
params.add(new BasicNameValuePair("redir", redir));//跳转地址，一般是自己主页
params.add(new BasicNameValuePair("source", "main"));
params.add(new BasicNameValuePair("login", "登录"));
httppost.setEntity(new UrlEncodedFormEntity(params));
CloseableHttpResponse response = httpclient.execute(httppost);//执行这个post

    int statuts\_code=response.getStatusLine().getStatusCode();//获得服务器返回状态码

    if(statuts\_code!=302){  
        System.err.println("登录失败~");  
        return false;  
    }

    else{  
        System.err.println("登录成功~");  
    }  
    httppost.releaseConnection();  
    return true;  
}

Step 2:利用火狐浏览器的firebug插件查看发帖时post哪些参数给服务器

一般是这4个参数：ck、rv_comment、start、submit_btn

发帖代码如下：

public static boolean startPost(String url) {//参数url即为帖子地址

    try{  
       String html=getPageHtml(url);  
       Pattern p=Pattern.compile("呃...你想要的东西不在这儿");  
       Matcher m=p.matcher(html);  
       if(m.find()){  
           return false;  
       }

       Pattern p3=Pattern.compile("该话题已被小组管理员设为不允许回应");  
       Matcher m3=p3.matcher(html);  
       if(m3.find()){  
           return false;  
       }

       Pattern p2=Pattern.compile("请输入上图中的单词");  
       Matcher m2=p2.matcher(html);  
       if(m2.find()){  
           System.out.println("要输验证码了~暂停10分钟");  
           Thread.sleep(600000);  
           return false;  
       }

    HttpPost httppost = new HttpPost(url+"add\_comment#last");  
    httppost.addHeader("Connection", "keep-alive");  
    List<NameValuePair> params2 = new ArrayList<NameValuePair>();  
    params2.add(new BasicNameValuePair("ck", "xNxg"));//这个参数很重要一定要自己用firebug查看，否则发不了贴  
    params2.add(new BasicNameValuePair("rv\_comment","你的评论内容"));//  
    params2.add(new BasicNameValuePair("start", "0"));  
    params2.add(new BasicNameValuePair("submit\_btn", "加上去"));  
    httppost.setEntity(new UrlEncodedFormEntity(params2,"utf-8"));  
    CloseableHttpResponse response = httpclient.execute(httppost);  
    int status\_code=response.getStatusLine().getStatusCode();

    if(status\_code==302){  
        System.out.println("评论成功~ "+url);//评论成功  
    }  
    else{  
        System.out.println("评论失败~ "+url);//评论失败  
    }  
    httppost.releaseConnection();  
    Thread.sleep(1500);  
    }catch(Exception e){  
        return false;  
    }

    return true;  

}

完整代码请查看我的GitHub:   https://github.com/wqpod2g/Douban

感谢这篇帖子的作者：http://www.cnblogs.com/lzzgym/p/3322685.html