java servlet/jsp随机验证码

package com.banding.web.util;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Random;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;

import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class Image extends HttpServlet {

//public static final long serialVersionUID = 1L ;

//private static final String CONTENT_TYPE = "text/html; charset=GBK";

public 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);

}

//Initialize global variables

public void init() throws ServletException {

}

//Process the HTTP Get request

public void doGet(HttpServletRequest request, HttpServletResponse response) throws

ServletException, IOException {

//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 = 60, 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(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 < 155; 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位数字)

String sRand = "";

for (int i = 0; i < 4; 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

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

}

// 将认证码存入SESSION

request.getSession().setAttribute("rand", sRand);

// 图象生效

g.dispose();

// 输出图象到页面

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

JPEGImageEncoder encode = JPEGCodec.createJPEGEncoder(response.

getOutputStream());

encode.encode(image);

}

//Clean up resources

public void destroy() {

}

}

上面的代码可以直接用，在web.xml中配置好以后就可以在浏览器中访问这个servlet，能得到下面的效果

若要在jsp页面中使用这个验证码 只需用一个 <img src="那个servlet的地址" />

这样就好了