Servlet:

package cn.bdqn.servlet;

import javax.imageio.ImageIO;

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 java.awt.*;

import java.awt.font.ImageGraphicAttribute;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Random;

@WebServlet(name = "Servlet",urlPatterns = "/yanCode")

public class Servlet extends HttpServlet {

    public void doPost(javax.servlet.http.HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        this.doGet(request,response);

    }

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

        String s="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

        Random random = new Random();

        int width=500;

        int height=50;

        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

        Graphics graphics = image.getGraphics();//相当于画笔

        //画背景

        graphics.setColor(Color.gray);

        graphics.fillRect(0,0,width,height);

        graphics.setColor(Color.black);

        for (int i = 0; i <4 ; i++) {

            int index = random.nextInt(s.length());

            String c = s.substring(index, index + 1);

            graphics.drawString(c,width/5*(i+1),15);

        }

        ImageIO.write(image,"jpg",response.getOutputStream());

    }

}

　　jsp:

<%--

  Created by IntelliJ IDEA.

  User: Administrator

  Date: 2017/10/10

  Time: 13:04

  To change this template use File | Settings | File Templates.

--%>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

  <head>

    <title>验证码</title>

  </head>

  <body>

  <img src="yanCode" alt="验证码"  style="width: 500px;height:50px">

  <input type="button" value="看不清,更换验证码" id="btn" onclick="changeCode();">

  <script type="text/javascript" src="js/jquery.min.js">

  </script>

  <script type="text/javascript" >

      function changeCode() {

          $("img").attr('src', 'yanCode?ts=' + new Date().getTime());

      }

  </script>

  </body>

</html>

巴特西

java实现网页验证码

Servlet:

jsp:

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