如何用Java实现模拟登录Discuz!论坛并下载返回的html代码？

以这个论坛为例：http://www.qiluyiyou.com，我现在想要用Java实现登录后获取返回的html代码，这是我的Java代码：package org.shaw;import java.io.IOException;
import java.io.UnsupportedEncodingException;
import org.apache.commons.httpclient.Cookie;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpException;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.httpclient.methods.PostMethod;public class BaiyouBBS
{
    static final String LOGON_SITE = "www.qiluyiyou.com";    static final int LOGON_PORT = 80;    public Cookie[] login(String name, String pas)
    {
        HttpClient client = new HttpClient();
        client.getHostConfiguration().setHost(LOGON_SITE, LOGON_PORT);
        PostMethod post = new PostMethod("http://www.qiluyiyou.com/logging.php?action=login");
        NameValuePair loginfield = new NameValuePair("loginfield", "username");
        NameValuePair username = new NameValuePair("username", name);
        NameValuePair password = new NameValuePair("password", pas);
        NameValuePair referer = new NameValuePair("referer", "http://www.qiluyiyou.com/index.php");
        NameValuePair questionid = new NameValuePair("questionid", "0");
        NameValuePair answer = new NameValuePair("answer", "");
        NameValuePair cookietime = new NameValuePair("cookietime", "2592000");
        post.setRequestBody(new NameValuePair[] { loginfield, username, password, referer, questionid, answer, cookietime });
        try
        {
            client.executeMethod(post);
        }
        catch (HttpException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        String responseString = null;
        try
        {
            responseString = new String(
                                        post.getResponseBodyAsString().getBytes(
                                                "gbk"));
            System.out.println(responseString);
        }
        catch (UnsupportedEncodingException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        Cookie[] cookies = client.getState().getCookies();
        client.getState().addCookies(cookies);
        post.releaseConnection();
        return null;
    }    public static void main(String[] args)
    {
        new BaiyouBBS().login("zzzxxxzzz", "zzzxxxzzz");
    }}结果每次返回的html代码都是登录页面的代码，本人百思不得其解。求高人写一个可以实现上述功能的Demo，本人感激不尽！分不多，只有30，全都用了，求各位高手解答！