动态生成验证码的简单实现

拼搏现实的明天。 2023-07-08 05:54 11阅读 0赞

> 功能描述：生成一张验证码并输出到页面上；点击验证码或文字，更换验证码

简单来说，就分三步：**生成一张图片 -> 美化图片 -> 将图片输出到页面**；话不多说，看代码：

*  验证码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.image.BufferedImage;
    import java.io.IOException;
    import java.util.Random;
    
    @WebServlet("/checkCodeServlet")
    public class CheckCodeServlet extends HttpServlet {
        
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            int width = 100;
            int height = 50;
    
            //1.创建一个对象，在内存中代表验证码图片对象
            BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
    
            //2.美化图片
            //2.1填充背景色
            Graphics g = image.getGraphics();//画笔对象
            g.setColor(Color.PINK);//设置画笔颜色
            g.fillRect(0,0,width,height);//填充背景色
            //2.2画边框(边框本来有1px的宽度)
            g.setColor(Color.BLUE);
            g.drawRect(0,0,width-1,height-1);
            //2.3写验证码
            //2.3.1生成随机的验证码
            String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
            	//生成随机角标
            Random ran = new Random();
            for(int i = 1; i <= 4; i++){
        
                int index = ran.nextInt(str.length());
                char ch = str.charAt(index);
                g.drawString(ch+"",width/5*i,height/2);//写验证码
            }
            //2.3.2画干扰线
            g.setColor(Color.CYAN);
            for(int i = 0; i < 10; i++){
        //随机生成坐标点
                int x1 = ran.nextInt(width);
                int x2 = ran.nextInt(width);
                int y1 = ran.nextInt(height);
                int y2 = ran.nextInt(height);
                g.drawLine(x1,y1,x2,y2);
            }
    
            //3.将图片输出到页面展示
            ImageIO.write(image,"jpg",response.getOutputStream());//将内存中的图片写到任意流里面去
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            this.doPost(request,response);
        }
    }

*  写一个html页面(JSP也可以)，显示验证码

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
        <script>
            /**
             *  给超链接和图片绑定单击事件
             */
            window.onload = function () {
        
                //1.获取图片对象
                var img = document.getElementById("checkCode");
                //2.绑定单击事件
                img.onclick = function () {
        
                    var date = new Date().getTime();
                    img.src = "/Response/checkCodeServlet?"+date;//加时间戳
                }
                var link = document.getElementById("change");
                link.onclick = img.onclick;
            }
        </script>
    </head>
    <body>
        <img id="checkCode" src="/Response/checkCodeServlet">
        <a id="change" href="">看不清？换一张</a>
    </body>
    </html>