Java生成验证码

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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

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