JavaWeb (三) 登陆页面验证码的实现

    在进行登陆的时候，往往会需要输入验证码，那么验证码是怎么实现的呢?

    首先我们的验证码图片是在JSP页面中展示的，所以先从JSP页面入手。

    流程：登录界面->后台生成图片和这个图片对应的数字（把数字存入session）->前台的jsp页面获得图片所对应的数字->当用户点击提交后判断用户输入的与存储的数字是否一样。

  1. 登录主页面（login.jsp）
  2. <%@ page language="java" contentType="text/html; charset=UTF-8"  
  3.     pageEncoding="UTF-8"%>  
  4. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
  5. <html>  
  6. <head>  
  7. <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">  
  8. <title>登录</title>  
  9. <script type="text/javascript">  
  10.     function refresh() {  
  11.         //IE存在缓存,需要new Date()实现更换路径的作用  
  12.         document.getElementById("image").src="../login/image.jsp?"+new Date();  
  13.     }  
  14. </script>  
  15. </head>  
  16. <body>  
  17.     <form action="../login/check.jsp" method="post" id="loginForm" name="loginForm">  
  18.         用户名：<input type="text" name="userName">  
  19.         密码：<input type="password" name="userPwd">  
  20.         验证码：<input type="text" name="code" maxlength="4">  
  21.         <img id="image" border="0"  onclick="refresh()" src="../login/image.jsp" title="点击更换图片">  
  22.         <input type="submit" value="登录">  
  23.     </form>  
  24. </body>  
  25. </html>  

     2. 验证码生成jsp(image.jsp)

  1. <%@page import="javax.imageio.ImageIO"%>  
  2. <%@page import="java.awt.Font"%>  
  3. <%@page import="java.awt.Graphics"%>  
  4. <%@page import="java.awt.image.BufferedImage"%>  
  5. <%@page import="java.util.Random"%>  
  6. <%@page import="java.awt.Color"%>  
  7. <%@ page language="java" contentType="image/JPEG; charset=UTF-8"  
  8.     pageEncoding="UTF-8"%>  
  9. <%!  
  10.     //获取随机颜色  
  11.     Color getRandColor(int fc,int bc){  
  12.     Random random = new Random();  
  13.     if(fc>255) fc=255;  
  14.     if(bc>255) bc=255;  
  15.     int r = fc + random.nextInt(bc - fc);  
  16.     int g = fc + random.nextInt(bc - fc);  
  17.     int b = fc + random.nextInt(bc - fc);  
  18.     return new Color(r,g,b);  
  19.     }  
  20. %>  
  21. <%  
  22.     //设置页面不缓存   
  23.     response.setHeader("Pragma", "No-cache");  
  24.     response.setHeader("Cache-Control", "no-cache");     
  25.     response.setDateHeader("Expires", 0);  
  26.     //在内存中创建图像  
  27.     int width = 60;  
  28.     int height = 20;  
  29.     BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);  
  30.     //获取图形上下文  
  31.     Graphics g = image.getGraphics();  
  32.     //随机类  
  33.     Random random = new Random();  
  34.     //设定背景  
  35.     g.setColor(getRandColor(200, 250));  
  36.     g.fillRect(0, 0, width, height);  
  37.     //设定字体  
  38.     g.setFont(new Font("Times New Roman",Font.PLAIN,18));  
  39.    //随机产生干扰线  
  40.    g.setColor(getRandColor(160, 200));     
  41.    for (int i = 0; i < 100; i++) {     
  42.         int x = random.nextInt(width);     
  43.         int y = random.nextInt(height);     
  44.         int xl = random.nextInt(12);     
  45.         int yl = random.nextInt(12);     
  46.         g.drawLine(x, y, x + xl, y + yl);     
  47.    }   
  48.    //随机产生4位验证码  
  49.    String[] codes = {"2","3","4","5","6","7","8","9","A","B","C","D","E","F","G","H","J","K","L","M","N","P","Q","R","S","T","U","V","W","X","Y","Z"};  
  50.    String code = "";  
  51.    for(int i=0;i<4;i++){  
  52.        String str = codes[random.nextInt(codes.length)];  
  53.        code += str;  
  54.        // 将认证码显示到图象中  
  55.        g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));  
  56.        //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成     
  57.        g.drawString(str, 13 * i + 6, 16);     
  58.    }  
  59.     // 将认证码存入SESSION     
  60.    session.setAttribute("code", code);  
  61.    // 图象生效     
  62.    g.dispose();     
  63.    // 输出图象到页面     
  64.    ImageIO.write(image, "JPEG", response.getOutputStream());  
  65.    //加上下面代码,运行时才不会出现java.lang.IllegalStateException: getOutputStream() has already been called ..........等异常  
  66.    response.getOutputStream().flush();    
  67.    response.getOutputStream().close();    
  68.    response.flushBuffer();    
  69.    out.clear();    
  70.    out = pageContext.pushBody();   
  71. %>  

     3. 验证码检查页面（check.jsp：检查验证码是否输入正确）

  72. <%@ page language="java" contentType="text/html; charset=UTF-8"  
  73.     pageEncoding="UTF-8"%>  
  74. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
  75. <html>  
  76. <head>  
  77. <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">  
  78. <title>验证</title>  
  79. <script type="text/javascript">  
  80.     function same(){  
  81.         loginForm.action = "login/login_login";  
  82.         loginForm.submit();  
  83.     }  
  84.     function different(){  
  85.         alert("请输入正确的验证码");  
  86.         location.href = "login.jsp";  
  87.     }  
  88. </script>  
  89. </head>  
  90. <body>  
  91.     <%  
  92.     String userName = request.getParameter("userName");  
  93.     String password = request.getParameter("userPwd");  
  94.     %>  
  95.     <form id="loginForm" name="loginForm" method="post">  
  96.         <input type="hidden" id="userName" value=<%=userName %>  name="user.userName">  
  97.         <input type="hidden" id="userPwd" value=<%=password %> name="user.userPwd">  
  98.     </form>  
  99.     <%  
  100.         String rand = session.getAttribute("code").toString();  
  101.         String input = request.getParameter("code");  
  102.         if(rand.equals(input)){  
  103.             out.println("<script language='javascript'>same();</script>");  
  104.         }else{  
  105.             out.print("<script language='javascript'>different();</script>");  
  106.         }  
  107.     %>  
  108. </body>  
</html>  
 

 最近学习了博主：孤傲苍狼的写法，在这里把它记录下来。

代码如下：

package com.qq.image;

/**
 * @Description:
 * @Author: ZHENGZHIQIANG
 * @CreateTime: 2019-03-25 16:45
 */

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
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;
/**
 * 生成随机图片，用来作为验证码
 */
@WebServlet("/imageServlet")
public class ImageServlet extends HttpServlet {
    private static final long serialVersionUID = 3038623696184546092L;

    public static final int WIDTH = 120;//生成的图片的宽度
    public static final int HEIGHT = 30;//生成的图片的高度

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

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String createTypeFlag = request.getParameter("createTypeFlag");//接收客户端传递的createTypeFlag标识
        //1.在内存中创建一张图片
        BufferedImage bi = new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_RGB);
        //2.得到图片
        Graphics g = bi.getGraphics();
        //3.设置图片的背影色
        setBackGround(g);
        //4.设置图片的边框
        setBorder(g);
        //5.在图片上画干扰线
        drawRandomLine(g);
        //6.写在图片上随机数
        //String random = drawRandomNum((Graphics2D) g,"ch");//生成中文验证码图片
        //String random = drawRandomNum((Graphics2D) g,"nl");//生成数字和字母组合的验证码图片
        //String random = drawRandomNum((Graphics2D) g,"n");//生成纯数字的验证码图片
        //String random = drawRandomNum((Graphics2D) g,"l");//生成纯字母的验证码图片
        String random = drawRandomNum((Graphics2D) g,createTypeFlag);//根据客户端传递的createTypeFlag标识生成验证码图片
        //7.将随机数存在session中
        request.getSession().setAttribute("checkcode", random);
        //8.设置响应头通知浏览器以图片的形式打开
        response.setContentType("image/jpeg");//等同于response.setHeader("Content-Type", "image/jpeg");
        //9.设置响应头控制浏览器不要缓存
        response.setDateHeader("expries", -1);
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "no-cache");
        //10.将图片写给浏览器
        ImageIO.write(bi, "jpg", response.getOutputStream());
    }

    /**
     * 设置图片的背景色
     * @param g
     */
    private void setBackGround(Graphics g) {
        // 设置颜色
        g.setColor(Color.WHITE);
        // 填充区域
        g.fillRect(0, 0, WIDTH, HEIGHT);
    }

    /**
     * 设置图片的边框
     * @param g
     */
    private void setBorder(Graphics g) {
        // 设置边框颜色
        g.setColor(Color.BLUE);
        // 边框区域
        g.drawRect(1, 1, WIDTH - 2, HEIGHT - 2);
    }

    /**
     * 在图片上画随机线条
     * @param g
     */
    private void drawRandomLine(Graphics g) {
        // 设置颜色
        g.setColor(Color.GREEN);
        // 设置线条个数并画线
        for (int i = 0; i < 5; i++) {
            int x1 = new Random().nextInt(WIDTH);
            int y1 = new Random().nextInt(HEIGHT);
            int x2 = new Random().nextInt(WIDTH);
            int y2 = new Random().nextInt(HEIGHT);
            g.drawLine(x1, y1, x2, y2);
        }
    }

    /**
     * 画随机字符
     * @param g
     * @param createTypeFlag
     * @return
     * String... createTypeFlag是可变参数，
     * Java1.5增加了新特性：可变参数：适用于参数个数不确定，类型确定的情况，java把可变参数当做数组处理。注意：可变参数必须位于最后一项
     */
    private String drawRandomNum(Graphics2D g,String... createTypeFlag) {
        // 设置颜色
        g.setColor(Color.RED);
        // 设置字体
        g.setFont(new Font("宋体", Font.BOLD, 20));
        //常用的中国汉字
        String baseChineseChar = "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";
        //数字和字母的组合
        String baseNumLetter = "0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ";
        //纯数字
        String baseNum = "0123456789";
        //纯字母
        String baseLetter = "ABCDEFGHJKLMNOPQRSTUVWXYZ";
        //createTypeFlag[0]==null表示没有传递参数
        if (createTypeFlag.length > 0 && null != createTypeFlag[0]) {
            if (createTypeFlag[0].equals("ch")) {
                // 截取汉字
                return createRandomChar(g, baseChineseChar);
            }else if (createTypeFlag[0].equals("nl")) {
                // 截取数字和字母的组合
                return createRandomChar(g, baseNumLetter);
            }else if (createTypeFlag[0].equals("n")) {
                // 截取数字
                return createRandomChar(g, baseNum);
            }else if (createTypeFlag[0].equals("l")) {
                // 截取字母
                return createRandomChar(g, baseLetter);
            }
        }else {
            // 默认截取数字和字母的组合
            return createRandomChar(g, baseNumLetter);
        }

        return "";
    }

    /**
     * 创建随机字符
     * @param g
     * @param baseChar
     * @return 随机字符
     */
    private String createRandomChar(Graphics2D g,String baseChar) {
        StringBuffer sb = new StringBuffer();
        int x = 5;
        String ch ="";
        // 控制字数
        for (int i = 0; i < 4; i++) {
            // 设置字体旋转角度
            int degree = new Random().nextInt() % 30;
            ch = baseChar.charAt(new Random().nextInt(baseChar.length())) + "";
            sb.append(ch);
            // 正向角度
            g.rotate(degree * Math.PI / 180, x, 20);
            g.drawString(ch, x, 20);
            // 反向角度
            g.rotate(-degree * Math.PI / 180, x, 20);
            x += 30;
        }
        return sb.toString();
    }
}
package com.qq.image;

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;

/**
 * @Description:
 * @Author: ZHENGZHIQIANG
 * @CreateTime: 2019-03-25 16:46
 */
@WebServlet("/CheckServlet")
public class CheckServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String clientCheckcode = request.getParameter("validateCode");//接收客户端浏览器提交上来的验证码
        String serverCheckcode = (String) request.getSession().getAttribute("checkcode");//从服务器端的session中取出验证码
        if (clientCheckcode.equals(serverCheckcode)) {//将客户端验证码和服务器端验证比较，如果相等，则表示验证通过
            System.out.println("验证码验证通过！");
        }else {
            System.out.println("验证码验证失败！");
        }
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <title>在Form表单中使用验证码</title>
    <script type="text/javascript">
        //刷新验证码
        function changeImg(){
            document.getElementById("validateCodeImg").src="/imageServlet?"+Math.random();
        }
    </script>
</head>

<body>
<form action="/CheckServlet" method="post">
    验证码：<input type="text" name="validateCode"/>
    <img alt="验证码看不清，换一张" src="/imageServlet" id="validateCodeImg" onclick="changeImg()">
    <a href="javascript:void(0)" onclick="changeImg()">看不清，换一张</a>
    <br/>
    <input type="submit" value="提交">
</form>
</body>
</html>

 

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原文地址：https://www.cnblogs.com/zqoceean/p/9461490.html