Java 验证码的实现

港控/mmm° 2022-06-08 14:24 253阅读 0赞

**java 验证码的实现**  
  
**1、绘制出一个随机验证码的Java类。**

package com.utils;
    
    import javax.imageio.ImageIO;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.awt.*;
    import java.awt.image.BufferedImage;
    import java.util.ArrayList;
    import java.util.Random;
    
    public class VerifyCode {
    
        private static ArrayList<Character> randString = new ArrayList<>();//随机产生的字符表
    
        static {//初始化验证码可选字符
            for (char i = 'a'; i <= 'z'; i++)
                randString.add(i);
            for (char i = 'A'; i <= 'Z'; i++)
                randString.add(i);
            for (char i = '0'; i <= '9'; i++)
                randString.add(i);
        }
    
        public static final String VERIFY_CODE_KEY = "VERIFY_CODE_KEY";//放到session中的key
        private static int width = 95;// 图片宽
        private static int height = 25;// 图片高
        private static int lineSize = 40;// 干扰线数量
        private static int stringNum = 4;// 随机产生字符数量
    
    
        private static Random random = new Random();
    
    
        /*
         * 获取随机字符
         */
        private static String getRandomString() {
            return String.valueOf(randString.get(random.nextInt(randString.size())));
        }
    
    
        /*
         * 获得字体
         */
        private static Font getFont() {
            return new java.awt.Font("Fixedsys", Font.BOLD, 20);
        }
    
    
        /*
         * 获得随机颜色
         */
        private static Color getRandColor(int fc, int bc) {
            if (fc > 255) fc = 255;
            if (bc > 255) bc = 255;
            int r = fc + random.nextInt(bc - fc - 16);
            int g = fc + random.nextInt(bc - fc - 14);
            int b = fc + random.nextInt(bc - fc - 18);
            return new Color(r, g, b);
        }
    
    
        /**
         * 生成随机图片
         */
        public static void getVerifydcode(HttpServletRequest request,
                                       HttpServletResponse response) {
            HttpSession session = request.getSession();
            // BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
            BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
            Graphics g = image.getGraphics();// 产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作
            g.fillRect(0, 0, width, height);
            g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
            g.setColor(getRandColor(110, 133));
            // 绘制干扰线
            for (int i = 0; i <= lineSize; i++) {
                drowLine(g);
            }
            // 绘制随机字符
            String randomString = "";
            for (int i = 1; i <= stringNum; i++) {
                randomString = drowString(g, randomString, i);
            }
            //将生成的随机字符串保存到session中，而jsp界面通过session.getAttribute("RANDOMCODEKEY")，
            //获得生成的验证码，然后跟用户输入的进行比较
            session.setAttribute(VERIFY_CODE_KEY, randomString);
            g.dispose();
            try {
                // 将内存中的图片通过流动形式输出到客户端
                ImageIO.write(image, "JPEG", response.getOutputStream());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
    
        /*
         * 绘制字符串
         */
        private static String drowString(Graphics g, String randomString, int i) {
            g.setFont(getFont());
            g.setColor(new Color(random.nextInt(101), random.nextInt(111), random
                    .nextInt(121)));
            String rand = String.valueOf(getRandomString());
            randomString += rand;
            g.translate(random.nextInt(3), random.nextInt(3));
            g.drawString(rand, 13 * i, 16);
            return randomString;
        }
    
    
        /*
         * 绘制干扰线
         */
        private static void drowLine(Graphics g) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            int xl = random.nextInt(13);
            int yl = random.nextInt(15);
            g.drawLine(x, y, x + xl, y + yl);
        }
    }

**2、创建一个servlet（用于请求生成验证码 VerifyCodeServlet.java）**

public class VerifyCodeServlet extends HttpServlet {
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            response.setContentType("image/jpeg");//设置相应类型,告诉浏览器输出的内容为图片
            response.setHeader("Pragma", "No-cache");//设置响应头信息，告诉浏览器不要缓存此内容
            response.setHeader("Cache-Control", "no-cache");//设置响应头信息，告诉浏览器不要缓存此内容
            response.setDateHeader("Expire", 0);//0为立刻过期，不让页面缓存该数据。
            try {
                //使用RandomValidateCode类绘制眼验证码并输出响应到response中
                VerifyCode.getVerifydcode(request, response);//输出验证码图片方法
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

**3、web.xml配置**

<servlet>
            <servlet-name>UserServlet</servlet-name>
            <servlet-class>com.servlet.UserServlet</servlet-class>
        </servlet>
        <servlet-mapping>
            <servlet-name>UserServlet</servlet-name>
            <url-pattern>login.user</url-pattern>
        </servlet-mapping>
    	
      <servlet>
            <servlet-name>VerifyCodeServlet</servlet-name>
            <servlet-class>com.servlet.VerifyCodeServlet</servlet-class>
        </servlet>
        <servlet-mapping>
            <servlet-name>VerifyCodeServlet</servlet-name>
            <url-pattern>/verifycode</url-pattern>
        </servlet-mapping>

**4、登录servlet验证(UserServlet.java)**

private void login(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            HttpSession session = request.getSession();
            String verifyCode = request.getParameter("verifyCode");//得到用户提交的验证码
            Object attribute = session.getAttribute(VerifyCode.VERIFY_CODE_KEY);//从session中取出生成的验证码
    		//如果用户提交的验证码为空，或者验证码忽略大小写比较不相等则退回到登录界面
            if (verifyCode == null || !verifyCode.equalsIgnoreCase(String.valueOf(attribute))) {
                request.setAttribute("tip", "验证码错误");
                request.getRequestDispatcher("/login.jsp").forward(request, response);
            }else{
    		//登录成功可以进行后续操作
    	}
    }

**5、登录页面login.jsp**

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>登录</title> 
        <script type="text/javascript">
            onload = function () {
                document.getElementById("img_vc").addEventListener("click", function (event) {
                    event.target.src = "/context/verifycode?" + Math.random(); //添加随机数是请求地址发生变化点击验证码图片重新获取验证码
                })
            }
        </script>
    </head>
    <body>
    
    <div id="content">
        <form id="from_login" action="login.user" method="post">
            <div>
                <input name="name" placeholder="用户名">
            </div>
            <div>
                <input name="psw" placeholder="密码">
            </div>
            <div>
                <input name="verifyCode" placeholder="验证码">
                <img id="img_vc" src="/context/verifycode" alt="获取验证码">
            </div>
            <div>
                <button id="btn_login" type="submit">登录</button>
            </div>  
        </form>
    </div>
    </body>
    </html>

**6、验证码截图**

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[Center]: /images/20220608/d00990a82cc041378e1407889fcd3507.png