Session应用之验证码

 1 package com.aeolia.view;
 2 
 3 import java.awt.Color;
 4 import java.awt.Font;
 5 import java.awt.image.BufferedImage;
 6 import java.io.IOException;
 7 import javax.imageio.ImageIO;
 8 import javax.servlet.ServletException;
 9 import javax.servlet.http.HttpServlet;
10 import javax.servlet.http.HttpServletRequest;
11 import javax.servlet.http.HttpServletResponse;
12 
13 public class CheckCode extends HttpServlet {
14     public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
15 
16         //禁止浏览器缓存随即图片
17         response.setDateHeader("Expires", -1);
18         response.setHeader("Cache-Control", "no-cache");
19         response.setHeader("Pragma", "no-cahce");
20         //通知客户机以图片方式打开发送过去的数据
21         response.setHeader("Content-Type","image/jpeg");
22         //在内存中创建一幅图片
23         java.awt.image.BufferedImage image=new BufferedImage(80,30,BufferedImage.TYPE_INT_RGB);
24         //向图片上写数据
25         java.awt.Graphics g=image.getGraphics();
26         //设置背景色
27         g.setColor(Color.white);
28         //设置矩形框
29         g.fillRect(0,0,80,30);
30         //设置背景色写入数据的字体和颜色
31         g.setColor(Color.red);
32         g.setFont(new Font(null,Font.BOLD,20));
33         //向图片上写数据
34         String nums=makeNums();
35         request.getSession().setAttribute("checkcode", nums);
36         g.drawString(nums, 0,20);
37         //把写好的数据的图片输出给浏览器
38         ImageIO.write(image, "jpg", response.getOutputStream());
39     }
40     private String makeNums() {
41         java.util.Random r=new java.util.Random();
42         String nums=r.nextInt(9999)+"";
43         StringBuffer sb=new StringBuffer(nums);
44         for(int i=0;i<4-nums.length();i++){
45             sb.append("0");
46         }
47         return sb.toString();
48     }
49     public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
50 
51         this.doGet(request, response);
52     }
53 }