javaee添加验证码

package com.zh.code;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferStrategy;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Random;

import javax.imageio.ImageIO;

import javax.jms.Session;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

public class CreateCode extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html");

        response.setHeader("Content", "image/jpeg");

        //7.禁止浏览器缓存 随机图片

        response.setDateHeader("Expires", -1);

        response.setHeader("Cache-Control", "no-cache");

        response.setHeader("Pragma", "no-cache");

        //1.创建一个图片的内在 bufferedImage

        //BufferedImage image=new BufferedImage(80, 30, BufferedImage.TYPE_INT_ARGB);

        BufferedImage image=new BufferedImage(50,30 , BufferedImage.TYPE_INT_BGR);

        //

        //2.得到image的画笔

        Graphics g=image.getGraphics();

        g.setColor(Color.CYAN);

        g.fillRect(0, 0, 50, 30);

        //在上面写数字

        g.setColor(Color.BLACK);

        g.setFont(new Font(null,Font.BOLD,20));

        String num=this.getCodeNum();

        g.drawString(num, 0, 20);

        //把得到的 验证码存在session中

        request.getSession().setAttribute("code", num);

        //3.图片发送

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

    }

    //返回的随机数据字符串

    public String getCodeNum(){

        Random randow=new Random();

        String num=randow.nextInt(9999)+"";

        StringBuffer stringBuffer=new StringBuffer("");

        for(int i=0;i<4-num.length();i++){

            stringBuffer.append("0");

        }

        num+=stringBuffer;

        return num;

    }

    /**

     * The doPost method of the servlet. <br>

     *

     * This method is called when a form has its tag value method equals to post.

     *

     * @param request the request send by the client to the server

     * @param response the response send by the server to the client

     * @throws ServletException if an error occurred

     * @throws IOException if an error occurred

     */

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html");

        this.doGet(request, response);

    }

}