jsp验证码

<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*,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=80, height=30;

BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文

//Graphics g = image.getGraphics();

Graphics2D g = image.createGraphics();

//生成随机类

Random random = new Random();

// 设定背景色

g.setColor(getRandColor(200,250));

g.fillRect(0, 0, width, height);

//设定字体

g.setFont(new Font("Times New Roman",Font.PLAIN,18));

//画边框

//g.setColor(new Color());

//g.drawRect(0,0,width-1,height-1);

// 随机产生188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<188;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);

}

// 取随机产生的认证码(4-6位数字)

int rdm = (int)(Math.random()*3+4);

String sRand="";

for (int i=0;i<rdm;i++){

String rand=String.valueOf(random.nextInt(10));

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

/*

*图片旋转

*/

AffineTransform at = new AffineTransform();

int number = random.nextInt(3)-1;

double role = number*random.nextDouble()*(Math.PI/2);

at.setToRotation(role,10*i,16);

g.setTransform(at);

/*

*图片旋转

*/

g.drawString(rand,10*i,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());

%>