用jsp生成随机验证码

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<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page contentType="image/jpeg"
import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%!Color getRandColor(int fc,int fb)
{

Random random = new Random();

if(fc>255) fc=255;

if(fb>255) fb=255;

int r=fc+random.nextInt(fb-fc);

int g=fc+random.nextInt(fb-fc);

int b=fc+random.nextInt(fb-fc);

return new Color(r,g,b);

} //获取随机颜色%>

<%
//去除页面缓存
response.setHeader("Pragma", "No-cache");

response.setHeader("Cache-Control", "no-cache");

response.setDateHeader("Expires", 0);

int width = 80; //定义验证码图片的长度

int height = 25; //定义验证码图片的宽度

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(0, 0, width, height);

g.setFont(new Font("Times New Roman", Font.PLAIN, 20));

//定义字体形式

g.setColor(getRandColor(160, 200));

for (int i = 0; i < 155; i++)

{

int i_x = random.nextInt(width);

int i_y = random.nextInt(height);

int i_xl = random.nextInt(12);

int i_yl = random.nextInt(12);

g.drawLine(i_x, i_y, i_x + i_xl, i_y + i_yl);

}

//用线条画背景

String s_Rand = "";

for (int i = 0; i < 4; i++)

{
  String rand ="";
  if(i<2){
   rand=String.valueOf((char)(random.nextInt(57)+65));//前两位字母
  }else{
   rand= String.valueOf(random.nextInt(10));//后两位数字
  }
  s_Rand += rand;

g.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));

//g.drawString(rand, 13 * i + 6, 16);
g.drawString(rand, 18 * i + 6, 20);

}

//产生4位随机码

session.setAttribute("rand", s_Rand);

//将验证码存入Session中

g.dispose();

ImageIO.write(image, "JPEG", response.getOutputStream());

//输出验证图片

out.clear();

out = pageContext.pushBody();
%>