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1. 创建一个servlet
1 package ztq.servlet.study; 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 16 public class ServletDemo1 extends HttpServlet { 17 public void doGet(HttpServletRequest request, HttpServletResponse response) 18 throws ServletException, IOException { 19 //通知浏览器不要缓存 20 response.setHeader("Expires", "-1"); 21 response.setHeader("Cache-Control", "no-cache"); 22 response.setHeader("Pragma", "no-cache"); 23 24 int width = 120; 25 int height = 25; 26 //创建一副内存图像 27 BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); 28 29 //得到属于该图像的画笔 30 Graphics g = bi.getGraphics(); 31 32 //画边框 33 g.setColor(Color.BLACK); 34 g.drawRect(0, 0, width, height); 35 36 //填充背景色 37 g.setColor(Color.GRAY); 38 g.fillRect(1, 1, width - 2, height - 2); 39 40 //画随机干扰线 41 g.setColor(Color.GREEN); 42 Random r = new Random(); 43 for(int i = 0; i < 10; i++){ 44 g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height)); 45 } 46 47 //画随机数字 48 g.setColor(Color.RED); 49 g.setFont(new Font("宋体", Font.BOLD|Font.ITALIC, 20)); 50 int x = 23; 51 for(int i = 0; i < 4; i++){ 52 g.drawString(r.nextInt(10) + "", x, 20); 53 x += 20; 54 } 55 56 //输出到浏览器的页面上 57 ImageIO.write(bi, "jpg", response.getOutputStream()); 58 59 } 60 public void doPost(HttpServletRequest request, HttpServletResponse response) 61 throws ServletException, IOException { 62 doGet(request, response); 63 } 64 }
2. 创建一个Html页面
1 <!DOCTYPE html> 2 <html> 3 <head> 4 <title>登录</title> 5 6 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 7 <meta http-equiv="description" content="this is my page"> 8 <meta http-equiv="content-type" content="text/html; charset=UTF-8"> 9 10 <!--<link rel="stylesheet" type="text/css" href="./styles.css">--> 11 12 </head> 13 14 <body> 15 <form action = "" method = "post"> 16 用户名：<input type = "text" name = "username" /><br /><br /> 17 密码： <input type = "password" name = "password" /><br /><br /> 18 验证码：<input type = "text" name = "code" /> 19 <img src = "/JavaWeb_Servlet_Study/servlet/ServletDemo1"> 20 <a href = "javascript:toRefresh()">看不清</a><br /><br /> 21 <input type = "submit" value = "登录" /> 22 </form> 23 <script type = "text/javascript"> 24 function toRefresh(){ 25 document.location.href = "login.html"; 26 } 27 </script> 28 </body> 29 </html>
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原文地址：http://www.cnblogs.com/zhangtianq/p/5918152.html
