import org.apache.commons.httpclient.Cookie;  
import org.apache.commons.httpclient.HttpClient;  
import org.apache.commons.httpclient.cookie.CookiePolicy;  
import org.apache.commons.httpclient.NameValuePair;  
import org.apache.commons.httpclient.methods.GetMethod;  
import org.apache.commons.httpclient.methods.PostMethod;


public class TestLogin {
     public static void main(String[] args) {  
            // 登陆 Url  
            String loginUrl = "http://139.196.40.80:3000/login";  
            // 需登陆后访问的 Url  
            String dataUrl = "http://139.196.40.80:3000/index";  
      
            HttpClient httpClient = new HttpClient();  
      
            // 模拟登陆，按实际服务器端要求选用 Post 或 Get 请求方式  
            PostMethod postMethod = new PostMethod(loginUrl);  
      
            // 设置登陆时要求的信息，用户名和密码  
            NameValuePair[] data = http://www.mamicode.com/{ new NameValuePair("username", "lixiuming"),  
                    new NameValuePair("password", "lixiuming") };  
            postMethod.setRequestBody(data);  
            try {  
                // 设置 HttpClient 接收 Cookie,用与浏览器一样的策略  
                httpClient.getParams().setCookiePolicy(  
                        CookiePolicy.BROWSER_COMPATIBILITY);  
                httpClient.executeMethod(postMethod);  
                // 获得登陆后的 Cookie  
                Cookie[] cookies = httpClient.getState().getCookies();  
                StringBuffer tmpcookies = new StringBuffer();  
                for (Cookie c : cookies) {  
                    tmpcookies.append(c.toString() + ";");
                   
                }
                // 进行登陆后的操作1581,1602,1603,1610,1609,1608,1607,1606,1605,1620,1619,1617,1616,1622,1626,1642,1648,1647,1657  
                GetMethod getMethod = new GetMethod(dataUrl);  
                // 每次访问需授权的网址时需带上前面的 cookie 作为通行证  
                getMethod.setRequestHeader("cookie", tmpcookies.toString());  
                // 你还可以通过 PostMethod/GetMethod 设置更多的请求后数据  
                // 例如，referer 从哪里来的，UA 像搜索引擎都会表名自己是谁，无良搜索引擎除外  
                postMethod.setRequestHeader("Referer", "http://139.196.40.80:3000/index");  
                postMethod.setRequestHeader("User-Agent", "www Spot");  
                httpClient.executeMethod(getMethod);  
                // 打印出返回数据，检验一下是否成功  
                String text = getMethod.getResponseBodyAsString();  
                System.out.println(text);  
            } catch (Exception e) {  
                e.printStackTrace();  
            }  
        }
}

httpClient 保持session