JavaWeb_HttpSession之验证码

￡神魔★判官ぃ 2023-08-17 17:40 81阅读 0赞

## 使用HttpSession实现验证码 ##

**1）基本原理：和表单重复提交一致：**

**　　>在原表单页面，生成一个验证码的图片，生成图片的同时，需要把该图片中的字符串放入session中。**

**　　>在原表单页面，定义一个文本域，用于输入验证码。**

**提交到servlet**

**　　>在目标的Servlet中:获取session和表单域中的验证码的值**

**　　>比较两个值是否一致：若一致，受理请求，且把Session域中的验证码的属性清除**

**　　>若不一致，则直接通过重定向的方式返回原表单页面，并提示用户"验证码错误"**

**index.jsp**

<%--
      Created by IntelliJ IDEA.
      User: dell
      Date: 2019/7/11
      Time: 17:31
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
    <font color="red">
    <%= session.getAttribute("message") == null? "" :session.getAttribute("message") %>
    </font>
    <form action="<%= request.getContextPath()%>/CheckCodeServlet" method="post">
        name: <input type="text" name="name">
        checkCode: <input type="text" name="CHECK_CODE_PARAM_NAME">
        <img src="<%= request.getContextPath()%>/ValidateColorServlet" alt="">
        <input type="submit" value=" Submit">
    </form>
    </body>
    </html>

**效果图：**

**![1642540-20190711175756872-431857427.png][]**

**验证码servlet**

package com.demo.servlet;
    
    import javax.imageio.ImageIO;
    import javax.servlet.ServletException;
    import javax.servlet.ServletOutputStream;
    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;
    
    public class ValidateColorServlet extends HttpServlet {
    
        public static final String CHECK_CODE_KEY="CHECK_CODE_KEY";
    
        //设置验证图片的宽度, 高度, 验证码的个数
        private int width = 152;
        private int height = 40;
        private int codeCount = 4;
    
        //验证码字体的高度
        private int fontHeight = 4;
    
        //验证码中的单个字符基线. 即：验证码中的单个字符位于验证码图形左上角的 (codeX, codeY) 位置处
        private int codeX = 0;
        private int codeY = 0;
    
        //验证码由哪些字符组成
        char [] codeSequence = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz23456789".toCharArray();
    
        //初始化验证码图形属性
        public void init(){
            fontHeight = height - 2;
            codeX = width / (codeCount + 2);
            codeY = height - 4;
        }
    
        public void service(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            //定义一个类型为 BufferedImage.TYPE_INT_BGR 类型的图像缓存
            BufferedImage buffImg = null;
            buffImg = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
    
            //在 buffImg 中创建一个 Graphics2D 图像
            Graphics2D graphics = null;
            graphics = buffImg.createGraphics();
    
            //设置一个颜色, 使 Graphics2D 对象的后续图形使用这个颜色
            graphics.setColor(Color.WHITE);
    
            //填充一个指定的矩形: x - 要填充矩形的 x 坐标; y - 要填充矩形的 y 坐标; width - 要填充矩形的宽度; height - 要填充矩形的高度
            graphics.fillRect(0, 0, width, height);
    
            //创建一个 Font 对象: name - 字体名称; style - Font 的样式常量; size - Font 的点大小
            Font font = null;
            font = new Font("", Font.BOLD, fontHeight);
            //使 Graphics2D 对象的后续图形使用此字体
            graphics.setFont(font);
    
            graphics.setColor(Color.BLACK);
    
            //绘制指定矩形的边框, 绘制出的矩形将比构件宽一个也高一个像素
            graphics.drawRect(0, 0, width - 1, height - 1);
    
            //随机产生 15 条干扰线, 使图像中的认证码不易被其它程序探测到
            Random random = null;
            random = new Random();
            graphics.setColor(Color.GREEN);
            for(int i = 0; i < 15; i++){
                int x = random.nextInt(width);
                int y = random.nextInt(height);
                int x1 = random.nextInt(20);
                int y1 = random.nextInt(20);
                graphics.drawLine(x, y, x + x1, y + y1);
            }
    
            //创建 randomCode 对象, 用于保存随机产生的验证码, 以便用户登录后进行验证
            StringBuffer randomCode;
            randomCode = new StringBuffer();
    
            for(int i = 0; i < codeCount; i++){
                //得到随机产生的验证码数字
                String strRand = null;
                strRand = String.valueOf(codeSequence[random.nextInt(36)]);
    
                //把正在产生的随机字符放入到StringBuffer中
                randomCode.append(strRand);
    
                //用随机产生的颜色将验证码绘制到图像中
                graphics.setColor(Color.BLUE);
                graphics.drawString(strRand, (i + 1)* codeX, codeY);
            }
            //在把存放有所有随机字符的StringBuffer对应的字符串放入到HttpSession中
            request.getSession().setAttribute(CHECK_CODE_KEY,randomCode.toString());
    
    
            //禁止图像缓存
            response.setHeader("Pragma", "no-cache");
            response.setHeader("Cache-Control", "no-cache");
            response.setDateHeader("Expires", 0);
    
            //将图像输出到输出流中
            ServletOutputStream sos = null;
            sos = response.getOutputStream();
            ImageIO.write(buffImg, "jpeg", sos);
            sos.close();
        }
    }

**CheckCodeServlet**

package com.demo.servlet;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    public class CheckCodeServlet  extends HttpServlet {
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
            //1.获取请求参数：CHECK_CODE_PARAM_NAME
            String paramCode = req.getParameter("CHECK_CODE_PARAM_NAME");
            //2.湖区session中CHECK_CODE_KEY属性值
            String sessionCode = (String) req.getSession().getAttribute("CHECK_CODE_KEY");
    
            System.out.println(paramCode);
            System.out.println(sessionCode);
    
            //3.比对，看是否一致，若一致说明验证码正确，若不一致，验证码错误
            if (!(paramCode!=null&&paramCode.equals(sessionCode))){
                req.getSession().setAttribute("message","验证码不一致");
                resp.sendRedirect(req.getContextPath()+"/check/index.jsp");
                return;
            }
            System.out.println("受理请求！");
        }
    }

![1642540-20190711180049574-550426123.png][]

![1642540-20190711180134132-1203867057.png][]

**区分大小写**

![1642540-20190711180248791-1460176170.png][]

转载于:https://www.cnblogs.com/yangHS/p/11171719.html

[1642540-20190711175756872-431857427.png]: /images/20230808/73832c13a8ec42c69adf1cb39cc20350.png
[1642540-20190711180049574-550426123.png]: /images/20230808/697fa684bc204bf7adffb36c6b6534c4.png
[1642540-20190711180134132-1203867057.png]: /images/20230808/fe00aed34ef7412d82469497107c6e12.png
[1642540-20190711180248791-1460176170.png]: /images/20230808/8b27509f5e384727b575ee091b87efd9.png