下面主要說明 Form-Based 的驗證方式的演示程式碼，如果登陸時需要一個驗證碼的話，那只有自己想辦法怎麼得到這個碼了：

package com.example.demo;

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

public class HttpClientLogin {
    public
    static void main(String[] args) {
        //登陸 Url
        String loginUrl = "http://192.168.1.100:8080/xx/login.do";

        //需登陸後訪問的 Url
        String dataUrl = "http://192.168.1.100:8999/xx/user_info.html?userid=123456";

        HttpClient httpClient = new HttpClient();

        //模擬登陸，按實際伺服器端要求選用 Post 或 Get 請求方式
        PostMethod postMethod = new PostMethod(loginUrl);

        //設定登陸時要求的資訊，一般就使用者名稱和密碼，驗證碼自己處理了
        NameValuePair[] data = {
                new NameValuePair("username", "aaa"),
                new NameValuePair("password", "123456"),
                new NameValuePair("code", "anyany")
        };

        postMethod.setRequestBody(data);

        try {
            //設定 HttpClient 接收 Cookie,用與瀏覽器一樣的策略
            httpClient.getParams().setCookiePolicy(CookiePolicy.BROWSER_COMPATIBILITY);

            httpClient.executeMethod(postMethod);

            //獲得登陸後的 Cookie
            Cookie[] cookies = httpClient.getState().getCookies();

            String tmpcookies = "";
            for (Cookie c : cookies) {
                tmpcookies += c.toString() + ";";
            }

            //進行登陸後的操作
            GetMethod getMethod = new GetMethod(dataUrl);

            //每次訪問需授權的網址時需帶上前面的 cookie 作為通行證
            getMethod.setRequestHeader("cookie", tmpcookies);

            //你還可以通過 PostMethod/GetMethod 設定更多的請求後資料
            //例如，referer 從哪裡來的，UA 像搜尋引擎都會表名自己是誰，無良搜尋引擎除外,這個也可以不要
//            postMethod.setRequestHeader("Referer", "http://localhost:8080");
//            postMethod.setRequestHeader("User-Agent", "aaa Spot");

            httpClient.executeMethod(getMethod);

            //打印出返回資料，檢驗一下是否成功
            String text = getMethod.getResponseBodyAsString();
            System.out.println(text);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
 

要引入jar包

<dependency>
	<groupId>commons-httpclient</groupId>
	<artifactId>commons-httpclient</artifactId>
	<version>3.0.1</version>
</dependency>