jar包验证码

1.将 jcaptcha.jar file into the WEB-INF/lib
2.创建ServletDemo4

package com.lanou3g.test;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.dsna.util.images.ValidateCode;

/**
 * Servlet implementation class ServletDemo4
 */
@WebServlet("/ServletDemo4")
public class ServletDemo4 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

//清空浏览器缓存
        response.setHeader("param", "no-cache");  
        response.setHeader("cache-control", "no-cache");  
        response.setIntHeader("expires", 0); 

        //生成一个宽为110，高为25，4个数字，5条干扰线的验证码
        ValidateCode validateCode = new ValidateCode(110, 25, 4, 5);
        validateCode.write(response.getOutputStream());

    }
}

3.创建Html








   

        username：


        password：


        code：
        看不清，换一张