简单验证码

<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<%@page import="java.awt.image.BufferedImage"%>
<%@page import="java.awt.*"%>
<%@page import="java.io.OutputStream"%>
<%@page import="com.sun.image.codec.jpeg.JPEGImageEncoder"%>
<%@page import="com.sun.image.codec.jpeg.JPEGCodec"%>
<%
//设置页面不缓存
response.setHeader("pragma","no-cache");
response.setHeader("cache-control","no-cache");
response.setDateHeader("expires",0);
response.setContentType("Image/gif");
 %>
<%
String s="";
int width=80,height=23;
char[] code=new char[]{
 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z',
 'a','b','c','d','e','f','g','h','i','j','k','l','m','n','p','q','r','s','t','u','v','w','x','y','z',
 '2','3','4','5','6','7','8','9'
};
Random random=new Random();
String strCode;
for(int i=0;i<4;i++)
{
	strCode=String.valueOf(code[random.nextInt(code.length)]);
	s=s+strCode;
}
//把得到的字符保存到session种
session.setAttribute("code",s);
//定义图像buffer
BufferedImage bufferedImage=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics2D gra=bufferedImage.createGraphics();
//填充背景颜色
gra.setColor(Color.white);
gra.fillRect(0,0,width,height);
gra.setFont(new Font("宋体",Font.BOLD+Font.ITALIC,20));  //设置字体样式
//画边框
gra.setColor(Color.blue);
gra.drawRect(0,0,width-1,height-1);
//产生干扰线
int x1=0,y1=0,x2=0,y2=0;
for(int i=0;i<30;i++)
{
x1=random.nextInt(100);
y1=random.nextInt(100);
x2=random.nextInt(100);
y2=random.nextInt(100);
gra.setColor(Color.black);
gra.drawLine(x1,y1,x1+x2,y1+y2);
}
//画出每个字符
char c;
for(int i=0;i<4;i++)
{
c=s.charAt(i);
gra.setColor(getColor());
gra.drawString(c+"",i*20+4,20);
}
OutputStream toClient=response.getOutputStream();
JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(toClient);
encoder.encode(bufferedImage);
toClient.close();
out.clear();
out=pageContext.pushBody();
 %>
 <%!
 private Color getColor()
 {
 Random random=new Random();
 int red=0,green=0,blue=0;
 red=random.nextInt(100);
 green=random.nextInt(100);
 blue=random.nextInt(100);
 return new Color(red,green,blue);
 }
 
  %>