JSP验证码的实现

       最近看SSH需要使用验证码，所以在网上找了一下。这个代码在网上已经流传很久了，大部分都大同小异，贴出来以备后用。
      代码如下(image.jsp)：
<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" %>
<%
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, width, height);
g.setColor(Color.black);
g.drawRect(0,0,width-1,height-1);
String rand =""+ (Math.random()*10000);
rand = rand.substring(0,rand.indexOf("."));
switch(rand.length())
{
case 1: rand = "000"+rand; break;
case 2: rand = "00"+rand; break;
case 3: rand = "0"+rand; break;
default: rand = rand.substring(0,4); break;
}
session.setAttribute("rand",rand);
g.setColor(Color.black);
Integer tempNumber = new Integer(rand);
String numberStr = tempNumber.toString();
g.setFont(new Font("Atlantic Inline",Font.PLAIN,18));
String Str = numberStr.substring(0,1);
g.drawString(Str,8,17);
Str = numberStr.substring(1,2);
g.drawString(Str,20,15);
Str = numberStr.substring(2,3);
g.drawString(Str,35,18);
Str = numberStr.substring(3,4);
g.drawString(Str,45,15);
Random random = new Random();
for (int i=0;i<250;i++)
{
int x = random.nextInt(width);
int y = random.nextInt(height);
g.drawOval(x,y,0,0);
}
g.dispose();
ImageIO.write(image,"JPEG", response.getOutputStream());
%>  
使用时通过<img alt="验证码" src="image.jsp">调用。