jsp实现验证码JSP彩色验证码的实现

image.jsp---------------------------------------------------------------------- 
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%> 
<% 
String path = request.getContextPath; 
String basePath = request.getScheme+"://"+request.getServerName+":"+request.getServerPort+path+"/"; 
%> 

<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %> 
<%! 
Color getRandColor( fc, bc){//给定范围获得随机颜色 
Random random =  Random; 
(fc>255) fc=255; 
(bc>255) bc=255; 
 r=fc+random.nextInt(bc-fc); 
 g=fc+random.nextInt(bc-fc); 
 b=fc+random.nextInt(bc-fc); 
  Color(r,g,b); 
} 
%> 
<% 
//设置页面不缓存Cache 
response.Header("Pragma","No-cache"); 
response.Header("Cache-Control","no-cache"); 
response.DateHeader("Expires", 0); 

// 在内存中创建图象 
 width=60, height=20; 
BufferedImage image =  BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); 

// 获取图形上下文 

Graphics g = image.getGraphics; 

//生成随机类 
Random random =  Random; 

// 设定背景色 
g.Color(getRandColor(200,250)); 
g.fillRect(0, 0, width, height); 

//设定字体 
g.Font( Font("Times New Roman",Font.PLAIN,18)); 

//画边框 
//g.Color( Color); 
//g.drawRect(0,0,width-1,height-1); 


// 随机产生155条干扰线使图象中认证码不易被其它探测到 
g.Color(getRandColor(160,200)); 
for ( i=0;i<155;i) 
{ 
 x = random.nextInt(width); 
 y = random.nextInt(height); 
 xl = random.nextInt(12); 
 yl = random.nextInt(12); 
g.drawLine(x,y,x+xl,y+yl); 
} 

// 取随机产生认证码(4位数字) 
String sRand="";