简单验证码生成

Java

import java.awt.Color;  
import java.awt.Font;  
import java.awt.Graphics;  
import java.awt.image.BufferedImage;  
import java.io.IOException;  
import java.util.Random;  
  
import javax.imageio.ImageIO;  
import javax.servlet.ServletException;  
import javax.servlet.http.HttpServlet;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
import javax.servlet.http.HttpSession;  
  
public class AuthImageServlet extends HttpServlet {  
  
   
    private static final long serialVersionUID = 1L;
    private static final String CONTENT_TYPE = "text/html; charset=utf-8";     
    //设置字母的大小,大小     
    private Font mFont = new Font("Times New Roman", Font.PLAIN, 17);     
    public void init() throws ServletException     
    {     
        super.init();     
    }     
    Color getRandColor(int fc,int bc)     
    {     
        Random random = new Random();     
        if(fc>255) fc=255;     
        if(bc>255) bc=255;     
        int r=fc+random.nextInt(bc-fc);     
        int g=fc+random.nextInt(bc-fc);     
        int b=fc+random.nextInt(bc-fc);     
        return new Color(r,g,b);     
    }     
    
    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException     
    {     
        response.setHeader("Pragma","No-cache");     
        response.setHeader("Cache-Control","no-cache");     
        response.setDateHeader("Expires", 0);     
        //表明生成的响应是图片     
        response.setContentType("image/jpeg");     
             
        int width=80, height=18;     
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);     
             
        Graphics g = image.getGraphics();     
        Random random = new Random();     
        g.setColor(getRandColor(200,250));     
        g.fillRect(1, 1, width-1, height-1);     
        g.setColor(new Color(102,102,102));     
        g.drawRect(0, 0, width-1, height-1);     
        g.setFont(mFont);     
    
        g.setColor(getRandColor(160,200));     
    
        //画随机线     
        for (int i=0;i<155;i++)     
        {     
            int x = random.nextInt(width - 1);     
            int y = random.nextInt(height - 1);     
            int xl = random.nextInt(6) + 1;     
            int yl = random.nextInt(12) + 1;     
            g.drawLine(x,y,x + xl,y + yl);     
        }     
    
        //从另一方向画随机线     
        for (int i = 0;i < 70;i++)     
        {     
            int x = random.nextInt(width - 1);     
            int y = random.nextInt(height - 1);     
            int xl = random.nextInt(12) + 1;     
            int yl = random.nextInt(6) + 1;     
            g.drawLine(x,y,x - xl,y - yl);     
        }     
    
        //生成随机数,并将随机数字转换为字母     
        String sRand="";     
        for (int i=0;i<4;i++)     
        {     
            int itmp = random.nextInt(26) + 65;     
            char ctmp = (char)itmp;     
            sRand += String.valueOf(ctmp);     
            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));     
            g.drawString(String.valueOf(ctmp),15*i+10,16);     
        }     
    
        HttpSession session = request.getSession(true);     
        session.setAttribute("rand",sRand);     
        g.dispose();     
        ImageIO.write(image, "JPEG", response.getOutputStream());     
    }     
    
}  

web.xml

<?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>AuthImageServlet</servlet-name>  
    <servlet-class>com.util.servlet.AuthImageServlet</servlet-class>  
  </servlet>  
  <servlet-mapping>  
    <servlet-name>AuthImageServlet</servlet-name>  
    <url-pattern>/servlet/AuthImageServlet</url-pattern>  
  </servlet-mapping>  
 
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

jsp

<%@ 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 changeCode() {
        var imgNode = document.getElementById("vimg");
        imgNode.src = "servlet/AuthImageServlet?t=" + Math.random(); // 防止浏览器缓存的问题       
    }
</script>
</head>

<body>
    <form action="checkServlet" method="post">
        <label>输入验证码</label><br />
        <input type="text" name="randomCode" />
        <img id="vimg" title="点击更换" onclick="changeCode();" src="servlet/AuthImageServlet"><br/> 
        <input type="submit" value="submit">
    </form>
</body>
</html>