JSP生成验证码源程序

<%@ page contentType="image/jpeg" import="java.awt.*,

java.awt.image.*,java.util.*,javax.imageio.*" %>

<%

// 在内存中创建图象

int width=60, height=20;

BufferedImage image = new BufferedImage(width, height,

BufferedImage.TYPE_INT_RGB);

// 获取图形上下文

Graphics g = image.getGraphics();

// 设定背景色

g.setColor(new Color(0xDCDCDC));

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

//画边框

g.setColor(Color.black);

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

// 取随机产生的认证码(4位数字)

String rand = request.getParameter("rand");

rand = rand.substring(0,rand.indexOf("."));

switch(rand.length())

{

case 1: rand = "000"+rand; break;

case 2: rand = "00"+rand; break;

case 3: rand = "0"+rand; break;

default: rand = rand.substring(0,4); break;

}

// 将认证码存入SESSION

session.setAttribute("rand",rand);

// 将认证码显示到图象中

g.setColor(Color.black);

Integer tempNumber = new Integer(rand);

String numberStr = tempNumber.toString();

g.setFont(new Font("Atlantic Inline",Font.PLAIN,18));

String Str = numberStr.substring(0,1);

g.drawString(Str,8,17);

Str = numberStr.substring(1,2);

g.drawString(Str,20,15);

Str = numberStr.substring(2,3);

g.drawString(Str,35,18);

Str = numberStr.substring(3,4);

g.drawString(Str,45,15);

// 随机产生88个干扰点，使图象中的认证码不易被其它程序探测到

Random random = new Random();

for (int i=0;i<20;i++)

{

int x = random.nextInt(width);

int y = random.nextInt(height);

g.drawOval(x,y,0,0);

}

// 图象生效

g.dispose();

// 输出图象到页面

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

%>