常用操作之点击图片动态生成验证码

最新推荐文章于 2023-03-10 16:31:06 发布

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#验证码 #动态

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博客提及login.jsp页面，表单提交后会请求到servlet页面，涉及网页表单提交与页面跳转的信息技术内容。

login.jsp页面

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2019/6/18
  Time: 15:58
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
    <script>
        function changeImg(){
            //发送请求获取验证码的图片,设置img图片
            //如果直接这样设定有问题,再次返回此页面，验证码不改变，因为每次会读取缓存下的, 添加盐值,告诉浏览器每次请求都是一次新的请求,不要读缓存
            document.getElementById("img").src="checkcode?time="+new Date().getTime();
        }
    </script>
</head>
<body>
<h1>用户登录</h1>
${error}
<form action="LoginServlet" method="post">
    用户名 <input type="text" name="username" ><br/>
    密&nbsp;&nbsp;&nbsp;&nbsp;码 <input type="text" name="password" ><br/>
    验证码 <input type="text" name="checkcode" ><br/>
    &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <img id="img" src="checkcode" onclick="changeImg()"> <a href="" onclick="changeImg()">看不清换一张</a><br/>
    <input type="submit">
</form>
</body>
</html>

表单提交后请求到的servlet页面

package web;

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.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
//在浏览器生成一个验证码
@WebServlet("/checkcode")
public class CheckCodeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //  创建画布
        int width = 120;
        int height = 40;
        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //  获得画笔
        Graphics g = bufferedImage.getGraphics();
        //  填充背景颜色
        g.setColor(Color.white);
        g.fillRect(0, 0, width, height);
        //  绘制边框
        g.setColor(Color.red);
        g.drawRect(0, 0, width - 1, height - 1);
        //  生成随机字符
        //  准备数据
        String data = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
        //  准备随机对象
        Random r = new Random();
        //  声明一个变量 保存验证码
        String code = "";
        //  书写4个随机字符
        for (int i = 0; i < 4; i++) {
            //  设置字体
            g.setFont(new Font("宋体", Font.BOLD, 28));
            //  设置随机颜色
            g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));

            String str = data.charAt(r.nextInt(data.length())) + "";
            g.drawString(str, 10 + i * 28, 30);

            //  将新的字符 保存到验证码中
            code = code + str;
        }
        //  绘制干扰线
        for (int i = 0; i < 6; i++) {
            //  设置随机颜色
            g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));

            g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height));
        }

        //  将验证码 打印到控制台
        System.out.println(code);

        //  将验证码放到session中
        request.getSession().setAttribute("code", code);

        //  将画布显示在浏览器中
        ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}