JSP生成验证码

<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<% //引用命名空间，并设置该页面的类型为图片类型 %>
<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
//利用随机数产生颜色（bc必须大于fc）
Color getRandColor(int fc,int bc)
{
 Random random = new Random();
 if(fc>255) fc=255;
 if(bc>255) bc=255;
 //产生三个随机数，然后定义出一种颜色
 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);
}
%>
<%
 out.clear();//这句针对resin服务器，如果是tomacat可以不要这句
 
 //response.setHeader("Pragma","No-cache");
 //response.setHeader("Cache-Control","no-cache");
 //response.setDateHeader("Expires", 0);
 int width=60, height=20;
 //设置图片的宽度、高度和图片类型。
 BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_BGR);
 Graphics g = image.getGraphics();
 Random random = new Random();
 //设置画笔的颜色
 g.setColor(getRandColor(200,250));
 //画一个矩形边框
 g.fillRect(0, 0, width, height);
 //设置画笔的字体
 g.setFont(new Font("Times New Roman",Font.PLAIN,18));
 g.setColor(getRandColor(160,200));
 //画干扰线
 for (int i=0;i<155;i++)
 {
  int x = random.nextInt(width);
  int y = random.nextInt(height);
  int xl = random.nextInt(12);
  int yl = random.nextInt(12);
  g.drawLine(x,y,x+xl,y+yl);
 }
 String sRand="";
 //将文字画入图片内
 for (int i=0;i<4;i++){
  String rand=String.valueOf(random.nextInt(10));
  sRand+=rand;
  g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
  g.drawString(rand,13*i+6,16);
 }
 // 将认证码存入SESSION
 session.setAttribute("rand",sRand);
 //释放资源，输出图片
 g.dispose();
 ImageIO.write(image, "JPEG", response.getOutputStream());
%>