jsp 验证码

<%@page import="javax.swing.ImageIcon"%>
<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%@page import="java.awt.geom.AffineTransform"%>
<%!
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);
    }
%>
<%
//设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

// 在内存中创建图象
int width=120, height=40;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文
Graphics2D g =  (Graphics2D)image.getGraphics();

//生成随机类
Random random = new Random();

// 设定背景色
g.setColor(getRandColor(200,250)); 
//g.setColor(new Color());
//g.drawRect(0,0,width-1,height-1)
g.fillRect(0, 0, width, height);

//设定字体
g.setFont(new Font("Times New Roman",Font.PLAIN, 32));
//画边框
// 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));


// 取随机产生的认证码(4位数字)
/*
for(int i=0; i < sRand.length(); i++) {
    String rand=String.valueOf(sRand.charAt(i));
    // 将认证码显示到图象中
    g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//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, 13*i + 6, 16);
}
*/
 char[]c={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','0','1','2','3','4','5','6','7','8'};
String sRand = "";
BasicStroke bs=new BasicStroke(1.5f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);    //创建一个供画笔选择线条粗细的对象
        g.setStroke(bs);
for (int i=0;i<6;i++){
    String rand=String.valueOf(c[random.nextInt(c.length)]);
    sRand+=rand;
    // 将认证码显示到图象中
    g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//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
    for (int j=0;j<2;j++)
    {
        int x = random.nextInt(width/6*(i+1));
        int y = random.nextInt(width/6*(i+1));
        int xl = random.nextInt(width);
        int yl = random.nextInt(width);
        g.drawLine(x,y,x+xl,y+yl);
    }
        AffineTransform at = new AffineTransform();
        int number = random.nextInt(3)-1;
        double role = number*random.nextDouble()*(Math.PI/4);
        at.setToRotation(role,18*i+2,24); //role:旋转角度,后面两个参数是设置围绕坐标点旋转
        g.setTransform(at);
        g.drawString(rand, 18*i+2, 24);
}
// 将认证码存入SESSION
session.setAttribute("validateCode",sRand);
// 图象生效
g.dispose();
// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
out.clear();   
out = pageContext.pushBody();  
%>