JavaWeb使用Response和Servlet生成验证码案例_黑马javaweb案例

末蓝、 2023-09-23 14:59 75阅读 0赞

> 黑马程序员JavaWeb网课案例笔记  
> 比较初级的验证码生成

### 文章目录 ###

*  一、验证码简介
 *  二、代码展示
 *  案例升级

# 一、验证码简介 #

验证码的本质：是一个图片，但是是存在内存的图片。（还是字母东倒西歪的图片）  
目的：防止恶意的表单注册

# 二、代码展示 #

1、生成验证码的逻辑CheckCodeServlet

package cn.itcast.web.servlet;
    
    import javax.imageio.ImageIO;
    import javax.servlet.ServletException;
    import javax.servlet.ServletOutputStream;
    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.创建一对象，在内存中生成图片(验证码图片对象)
            BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);//参数：宽，高，图片类型
    
    
            //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);//前两个参数x，y为起始点
    
            //2.2画边框
            g.setColor(Color.BLUE);
            g.drawRect(0,0,width - 1,height - 1);
            //设置字体大小。好像没成
            Font font = new Font("copperplate",Font.BOLD,50);
            g.setFont(font);
    
            String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
            //生成随机角标(下标)
            Random ran = new Random();
    
            //四位验证码，循环四次
            for (int i = 1; i <= 4; i++) {
        
                int index = ran.nextInt(str.length());
                //获取字符
                char ch = str.charAt(index);//随机字符
                //2.3写验证码
                g.drawString(ch+"",width/5*i,height/2);
            }
    
    
            //2.4画干扰线
            g.setColor(Color.GREEN);
            //随机生成坐标点
            for (int i = 0; i < 10; i++) {
        //画十条线
                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());
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            this.doPost(request,response);
        }
    }

简单的页面展示，单击切换验证码

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>验证码</title>
    
        <script>
            /*
                分析：
                    点击超链接或者图片，需要换一张
                    1.给超链接和图片绑定单击事件
    
                    2.重新设置图片的src属性值
             */
        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(){
                //加时间戳
                var date = new Date().getTime();
    
                img.src = "/day15/checkCodeServlet?"+date;//后面加一个永不重复的无意义的数，欺骗电脑缓存。因为？后没用
            }
    
            var a = document.getElementById("change");
            a.onclick = function (){
                var data = new Date().getTime();
                a.href = "/day15/checkCodeServlet?"+date;
            }
    
        }
    
    
        </script>
    
    
    </head>
    <body>
    
        
        <img id="checkCode" src="/day15_response_war_exploded/checkCodeServlet" />
    
        <a id="change" href="">看不清换一张？</a>
    
    </body>
    </html>

# 案例升级 #

[JavaWeb实现简单的带有验证码的用户判断登录案例][JavaWeb]  
来源：B站黑马程序员JavaWeb网课

[JavaWeb]: https://blog.csdn.net/mfysss/article/details/127831197?csdn_share_tail=%7B%22type%22:%22blog%22,%22rType%22:%22article%22,%22rId%22:%22127831197%22,%22source%22:%22mfysss%22%7D