session的典型案例三:实现一次性验证码

灰太狼 2022-06-07 03:17 142阅读 0赞

生成验证码的工具类：

package com.sa.util;
    import java.awt.Color;
    import java.awt.Font;
    import java.awt.Graphics2D;
    import java.awt.image.BufferedImage;
    import java.io.IOException;
    import java.util.Random;
    
    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 javax.servlet.http.HttpSession;
    
    import com.sun.image.codec.jpeg.JPEGCodec;
    import com.sun.image.codec.jpeg.JPEGImageEncoder;
    
    /**
     * 验证码图片生成Servlet类，直接调用该Servlet即可使用
     * 取值的时候调用session.getAttribute("code")得到生成的值
     * @author <a href="mailto:weijunqiang2010@gmail.com">Ajunboys</a>
     *
     */
    @WebServlet("/verifycode")
    public class VerifyCodeUtil extends HttpServlet {
        private static final long serialVersionUID = 1L;
    
        static final char[] dictionary = {
                '2','3','4','5','6','7','8','9'
                ,'a','b','c','d','e','f','g','h','i','j'
                ,'k','m','n','p','q','r','s','t'
                ,'u','v','w','x','y','z'
                ,'A','B','C','D','E','F','G','H','J'
                ,'K','L','M','N','P','Q','R','S','T'
                ,'U','V','W','X','Y','Z'
                /*'1','l','0','O','o','#','@','$','%','&','(',')','|','/','*'//暂时不用特殊字符(包括：数字1,0；字母：l,o,O)
                ,'^','!','~','\\'*/
        };
        static Random random = new Random();
    
        /**
         * 产生n[4,4+]个随机数
         * @param n
         * @return
         */
        static String getRandomString(int n){
            StringBuffer buffer = new StringBuffer();
            if (n < 4) {
                n = 4;
            }
            for (int i = 0; i < n; i++) {
                buffer.append(dictionary[random.nextInt(dictionary.length)]);
            }
            return buffer.toString();
        }
    
        /**
         * 随机颜色
         * @return
         */
        static Color getRandomColor(){
            return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255));
        }
    
        /**
         * 颜色反色
         * @param c
         * @return
         */
        static Color getReverseColor(Color c){
            return new Color(255 - c.getRed(), 255 - c.getGreen(), 255 - c.getBlue());
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doPost(request, response);
        }
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            response.setContentType("image/jpeg");
    
            String randomString = getRandomString(6);
    
            request.getSession(true).setAttribute("code", randomString);
    
            int width = 100; //验证码图片宽度
            int height = 30; //验证码图片高度
    
            Color color = getRandomColor();
    
            Color reverse = getReverseColor(color);
    
            //创建一个彩图
            BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    
            //绘图对象
            Graphics2D g = bi.createGraphics();
    
            g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));
            g.setColor(color);
            g.fillRect(0, 0, width, height);
            g.setColor(reverse);
            g.drawString(randomString, 18, 20);
    
            //绘制最多100个噪音点
            for (int i = 0, n = random.nextInt(100); i < n; i++) {
                g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
            }
    
            ServletOutputStream out = response.getOutputStream();
    
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
    
            encoder.encode(bi);
    
            out.flush();
    
            out.close();
        }
    
    }

登录页面：

<%--
      Created by IntelliJ IDEA.
      User: 123
      Date: 2017/10/9
      Time: 8:57
      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>
        <script>
    
            function reload() {
                console.log(1);
                var img = document.getElementById("img");
                img.src = "<%=request.getContextPath()%>/verifycode?num="+Math.random();
                //img.src=img.src
            }
        </script>
    </head>
    <body>
        <form action="<%=request.getContextPath()%>/loginServlet" method="post">
            name:<input type="text" name="name"/>
            password:<input type="password" name="password"/>
            verify:<input type="text" name="verify"/>
            <img src="<%=request.getContextPath()%>/verifycode" id="img"/>
            <a href="javascript:reload();">看不清,换一张?</a>
            <input type="submit" value="提交">
        </form>
    </body>
    </html>

逻辑判断：

package com.sa.servlet;
    
    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.io.IOException;
    
    //@WebServlet(name = "loginServlet")
    public class LoginServlet extends HttpServlet {
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            System.out.println(1);
            String verifyCode=(String) request.getParameter("verify");
              String code=(String) request.getSession().getAttribute("code");
              if(code.equalsIgnoreCase(verifyCode)){
                  response.sendRedirect(request.getContextPath()+"/pages/success.jsp");
              }else{
                  response.sendRedirect(request.getContextPath()+"/pages/failed.jsp");
              }
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        }
    }

测试：

![Center][]

![Center 1][]

[Center]: /images/20220607/33ffc15480eb48a09ac61d2bd675f4ed.png
[Center 1]: /images/20220607/d56510d68c9e47d89232cf8cedbc3522.png