本文是一个很简单的向网页上输出验证码的实现喲！通过注释解释清楚了每一步！
Myeclipse下的Package Explorer显示文件结构如下：
ResponseDemo.java实现了输出随机图片的功能：
1 package com.yyz.response;
2
3 import java.awt.Color;
4 import java.awt.Font;
5 import java.awt.Graphics;
6 import java.awt.image.BufferedImage;
7 import java.io.IOException;
8 import java.util.Random;
9
10 import javax.imageio.ImageIO;
11 import javax.servlet.ServletException;
12 import javax.servlet.http.HttpServlet;
13 import javax.servlet.http.HttpServletRequest;
14 import javax.servlet.http.HttpServletResponse;
15 //输出随机图片
16 public class ResponseDemo extends HttpServlet {
17
18 public void doGet(HttpServletRequest request, HttpServletResponse response)
19 throws ServletException, IOException {
20 //6.设置头，控制浏览器不要缓存图片数据
21 response.setHeader("Expires", "-1");
22 response.setHeader("Cache-Control", "no-cache");
23 response.setHeader("Pragma", "no-cache");
24
25 //5.通知浏览器以图片方式打开
26 response.setHeader("Content-type", "image/jpeg");
27 //1.在内存中创建一副图片
28 BufferedImage image = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
29 //2.得到图片
30 Graphics g = image.getGraphics();
31 //修改图片背景色
32 g.setColor(Color.WHITE);
33 g.fillRect(0, 0,80, 20);
34 //3.向图片上写数据
35 g.setColor(Color.BLUE);
36 g.setFont(new Font(null,Font.BOLD,20));
37 g.drawString(nakeNum(), 0, 20);
38 //随机画出9条干扰线
39 Random rand = new Random();
40 for(int i = 0;i<9;i++){
41 g.setColor(Color.BLACK);
42 int x1 = rand.nextInt(80);
43 int y1 = rand.nextInt(20);
44 int x2 = rand.nextInt(80);
45 int y2 = rand.nextInt(20);
46 g.drawLine(x1, y1, x2, y2);
47 }
48 //4.将图片写给浏览器
49 ImageIO.write(image, "jpeg", response.getOutputStream());
50
51 }
52
53 private String nakeNum() {
54 Random r = new Random();
55 String num = r.nextInt(9999999)+"";//产生0-9999999的数字，但有可能不足7位，如123
56 StringBuffer sb = new StringBuffer();
57 for(int i = 0;i<7-num.length();i++){
58 sb.append("0");
59 }
60 return sb.toString()+num;
61 }
62
63 public void doPost(HttpServletRequest request, HttpServletResponse response)
64 throws ServletException, IOException {
65 doGet(request,response);
66 }
67 }
register.html是一个简单的注册页面，通过img标签执行ResponseDemo.java:
1 <!DOCTYPE html> 2 <html> 3 <head> 4 <title>register.html</title> 5 <meta name="keywords" content="keyword1,keyword2,keyword3"> 6 <meta name="description" content="this is my page"> 7 <meta name="content-type" content="text/html; charset=UTF-8"> 8 </head> 9 <body> 10 <form action=""> 11 用户名：<input type="text" name="username"> 12 密码：<input type="password" name="password"> 13 认证码：<input type="text" name="checkcode"><img src="/day06/servlet/ResponseDemo"> 14 <input type="submit " value="注册"> <br> 15 <br> 16 </body> 17 </html>
最后附上测试结果：
输出随机图片时，图片上若想要输出中文，可以用一个字符数组存储多个汉字（直接存汉字的编码也行），然后用Random产生的随机数做下标取出对应中文，再产生要写上图片的字符串即可。
时间： 2024-10-06 22:27:09