【开发技术】Java生成验证码

Java生成验证码

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="data: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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【开发技术】Java生成验证码

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