servlet写的验证码

package com.wsx;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.PrintWriter;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class CreateCode extends HttpServlet {/** * Constructor of the object. */public CreateCode() {super();}/** * Destruction of the servlet. <br> */public void destroy() {super.destroy(); // Just puts "destroy" string in log// Put your code here}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html ;charset=utf-8");//防止浏览器缓存随机图片        response.setDateHeader("Expires", -1);        response.setHeader("Cache-Control", "no-cache");        response.setHeader("Pragna", "no-cache");        //通知客户机以图片方式打开发送过去的数据        response.setHeader("Content-Type", "image/jpeg");        //1、在内存中创建一副图片        BufferedImage image=new BufferedImage(80,30,BufferedImage.TYPE_INT_RGB);        //2、向图片上写数据        Graphics g=image.getGraphics();//获得画笔        //设置背景色        g.setColor(Color.WHITE);        g.fillRect(0, 0, 80,30);//矩形框        //3、设置写入数据的颜色和字体        g.setColor(Color.BLACK);        g.setFont(new Font(null,Font.BOLD,20));        //4、向图片上写数据        String num=makeNum();        request.getSession().setAttribute("checkcode", num);        g.drawString(num, 0,20);        //把写好的数据的图片输出给浏览器        ImageIO.write(image, "jpg", response.getOutputStream());        //该函数用于生成7位数字       } public String makeNum() {     Random r=new Random();          //999999用来产生7位数，因此你可以修改999999来生成你要的验证码位数     String num=r.nextInt(9999999)+"";     StringBuffer sb=new StringBuffer();     //如果不够7位前面补0     for(int i=0;i<7-num.length();i++){     sb.append("0");     }     num=sb.toString()+num;     return num;     }public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}/** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */public void init() throws ServletException {// Put your code here}}

使用方法：

<img src='验证码的url'>   out.println("验证码:<input type='text' name='checkcode'/><img src='/mycheckcode/CreateCode'/><br/>");