jsp

[color=brown][/color] [/size][size=medium]<%@ page language="java" import="java.awt.*,java.util.*,java.awt.image.*,javax.imageio.*" pageEncoding="GBK"%>
<%@ page import="java.io.OutputStream" %> 
<%!
Color getRandColor(int fc,int bc){//给定范围获得随机颜色
        Random random = new Random();
        if(fc>255) fc=255;
        if(bc>255) bc=255;
        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);
        }
%>
<%
try{ 
//设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
OutputStream os=response.getOutputStream(); 
// 在内存中创建图象
int width=100, height=20;
BufferedImage image = new 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 = new Random();

// 设定背景色
g.setColor(getRandColor(180,250));
g.fillRect(0, 0, width, height);
//用于随机的字体的集合
String[] fontNames = {"Times New Roman","Book antiqua","Arial","Ludovicos","Sans-serif"};  
       
//画边框
g.setColor(new Color(0,0,0));
g.drawRect(0,0,width-1,height-1);


// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(getRandColor(160,200));
for (int i=0;i<90;i++)
{
int x = random.nextInt(width);
int y = random.nextInt(height);
        int xl = random.nextInt(14);
        int yl = random.nextInt(12);
g.drawLine(x,y,x+xl,y+yl);
}

// 取随机产生的认证码(4位数字)
String sRand="";
for (int i=0;i<5;i++){
//设置字体
g.setFont(new Font(fontNames[random.nextInt(5)] , Font.ITALIC , height));
String rand = null;
if(random.nextInt(10) > 5){
rand = String.valueOf((char)(random.nextInt(10) + 48));
} else {
rand = String.valueOf((char) (random.nextInt(26) + 65));
}
sRand += rand;
    // 将认证码显示到图象中
    g.setColor(new Color(random.nextInt(100),random.nextInt(80),random.nextInt(80)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
    g.drawString(rand,15*i+10,16);
}

// 将认证码存入SESSION
session.setAttribute("rand",sRand);


// 图象生效
g.dispose();

// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
//注意看以下几句的使用  
os.flush();  
os.close();  
os=null;  
response.flushBuffer();  
out.clear();  
out = pageContext.pushBody(); 
}  
catch(IllegalStateException e)  
{  
System.out.println(e.getMessage());  
e.printStackTrace();  
}
%>