Java EE登陆界面生成随机数防止恶意注册或者登录

1. package cn.com;  
2.   
3.   
4. import java.awt.Color;  
5. import java.awt.Font;  
6. import java.awt.Graphics;  
7. import java.awt.Graphics2D;  
8. import java.awt.image.BufferedImage;  
9. import java.io.IOException;  
10. import java.util.Random;  
11.   
12. import javax.imageio.ImageIO;  
13. import javax.servlet.ServletException;  
14. import javax.servlet.http.HttpServlet;  
15. import javax.servlet.http.HttpServletRequest;  
16. import javax.servlet.http.HttpServletResponse;  
17.   
18. public class ResponseDemoRandom extends HttpServlet {  
19.     private static final long serialVersionUID = 1L;  
20.     public static final int WIDTH=120;  
21.     public static final int HEIGHT=25;  
22.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  
23.         BufferedImage image=new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);  
24.         Graphics g=image.getGraphics();  
25.         //设置背景色  
26.         setBackGround(g);  
27.           
28.         //设置边框  
29.         setBorder(g);  
30.           
31.         //画干扰线  
32.         drawRandomLine(g);  
33.           
34.         //写随机数  
35.         drawRandomNum((Graphics2D)g);  
36.           
37.         response.setContentType("image/jpeg");  
38.         response.setDateHeader("expries", -1);  
39.         response.setHeader("Cache-Control", "no-control");  
40.         response.setHeader("prama", "no-control");  
41.         ImageIO.write(image, "jpg", response.getOutputStream());  
42.     }  
43.   
44.     private void drawRandomNum(Graphics2D g) {  
45.         g.setColor(Color.PINK);  
46.         g.setFont(new Font("宋体",Font.BOLD,20));  
47.         int x=10;  
48.         for(int i=0;i<4;i++)  
49.         {  
50.             int degree=new Random().nextInt()%30;  
51.             int num=new Random().nextInt(9);  
52.             String str=num+"";  
53.             g.rotate(degree*Math.PI/180, x, 20);  
54.             g.drawString(str, x, 20);  
55.             g.rotate(-degree*Math.PI/180, x, 20);  
56.             x+=30;  
57.         }  
58.           
59.     }  
60.   
61.     private void drawRandomLine(Graphics g) {  
62.         g.setColor(Color.blue);  
63.         for(int i=0;i<5;i++)  
64.         {  
65.             int x1=new Random().nextInt(WIDTH-4)+2;  
66.             int y1=new Random().nextInt(HEIGHT-4)+2;  
67.               
68.             int x2=new Random().nextInt(WIDTH-2);  
69.             int y2=new Random().nextInt(HEIGHT-2);  
70.               
71.             g.drawLine(x1, y1, x2, y2);  
72.               
73.         }  
74.           
75.     }  
76.   
77.     private void setBorder(Graphics g) {  
78.         g.setColor(Color.GREEN);  
79.         g.drawRect(1, 1, WIDTH-2, HEIGHT-2);  
80.     }  
81.   
82.     private void setBackGround(Graphics g) {  
83.         g.setColor(Color.gray);  
84.         g.fillRect(0, 0, WIDTH, HEIGHT);  
85.     }  
86.   
87.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  
88.         doGet(request,response);  
89.     }  
90.   
91. }