(Java 功能篇) Java 验证码

- 日理万妓 2023-10-10 10:49 41阅读 0赞

为了防止用户恶意,或者使用软件外挂提交一些内容,就得用验证码来阻止,虽然这个会影响用户体验,但为了避免一些问题很多网站都使用了验证码;今天下午参考文档弄了一个验证码,这里分享一下;这是一个web工程,首先是页面,这里只是一个显示验证码页面index.jsp,使用默认生成的就可以了,表单没有做提交,如下

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <title>验证码</title>
        <script type="text/javascript">
        function refresh(obj) {
            obj.src = "imageServlet?"+Math.random();
        }
        </script>
      </head>
      <body>
        <form action="checkServlet" method="post">
            <label>输入验证码</label><br/>
            <input type="text" name="randomCode"/><img title="点击更换" onclick="javascript:refresh(this);" src="imageServlet"><br/>
            <input type="submit" value="submit">
        </form>
      </body>
    </html>

下面是后台代码,这里是一个Servlet,不要忘记在web.xml中配置请求url

package com.wf.web;
    
    import java.io.IOException;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class ImageServlet extends HttpServlet {
    
        private static final long serialVersionUID = 1L;
    
        public 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");
            response.setDateHeader("Expire", 0);
            RandomValidateCode randomValidateCode = new RandomValidateCode();
            try {
                randomValidateCode.getRandcode(request, response);//输出图片方法
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request, response);
        }
    
    }

这个类是生成验证码的方法,如下

package com.wf.web;
    
    import java.awt.Color;
    import java.awt.Font;
    import java.awt.Graphics;
    import java.awt.image.BufferedImage;
    import java.util.Random;
    
    import javax.imageio.ImageIO;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    
    public class RandomValidateCode {
    
        public static final String RANDOMCODEKEY = "RANDOMVALIDATECODEKEY";//放到session中的key
        private Random random = new Random();
        private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生的字符串
        
        private int width = 80;//图片宽
        private int height = 26;//图片高
        private int lineSize = 40;//干扰线数量
        private int stringNum = 4;//随机产生字符数量
        /*
         * 获得字体
         */
        private Font getFont(){
            return new Font("Fixedsys",Font.CENTER_BASELINE,18);
        }
        /*
         * 获得颜色
         */
        private 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 void getRandcode(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.ROMAN_BASELINE,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);
            }
            session.removeAttribute(RANDOMCODEKEY);
            session.setAttribute(RANDOMCODEKEY, randomString);
            System.out.println(randomString);
            g.dispose();
            try {
                ImageIO.write(image, "JPEG", response.getOutputStream());//将内存中的图片通过流动形式输出到客户端
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        /*
         * 绘制字符串
         */
        private 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(random.nextInt(randString.length())));
            randomString +=rand;
            g.translate(random.nextInt(3), random.nextInt(3));
            g.drawString(rand, 13*i, 16);
            return randomString;
        }
        /*
         * 绘制干扰线
         */
        private 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);
        }
        /*
         * 获取随机的字符
         */
        public String getRandomString(int num){
            return String.valueOf(randString.charAt(num));
        }
    }

这里附带吧web.xml也加上吧,希望对初学者有帮助

<?xml version="1.0" encoding="UTF-8"?>
    <web-app version="2.5" 
        xmlns="http://java.sun.com/xml/ns/javaee" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
        http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
      <servlet>
        <servlet-name>ImageServlet</servlet-name>
        <servlet-class>com.wf.web.ImageServlet</servlet-class>
      </servlet>
    
      <servlet-mapping>
        <servlet-name>ImageServlet</servlet-name>
        <url-pattern>/imageServlet</url-pattern>
      </servlet-mapping>
      <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
      </welcome-file-list>
    </web-app>

就这么多,验证码是保存在session中的,或者cookie也行,但都要必须及时清除