CheckCodeServlet.java
1 import java.awt.Color; 2 import java.awt.Font; 3 import java.awt.Graphics; 4 import java.awt.image.BufferedImage; 5 import java.io.IOException; 6 import java.util.Random; 7 import javax.imageio.ImageIO; 8 import javax.servlet.ServletException; 9 import javax.servlet.annotation.WebServlet; 10 import javax.servlet.http.HttpServlet; 11 import javax.servlet.http.HttpServletRequest; 12 import javax.servlet.http.HttpServletResponse; 13 14 /** 15 * 验证码 16 */ 17 @WebServlet("/checkCodeServlet") 18 public class CheckCodeServlet extends HttpServlet { 19 public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { 20 21 //服务器通知浏览器不要缓存 22 response.setHeader("pragma","no-cache"); 23 response.setHeader("cache-control","no-cache"); 24 response.setHeader("expires","0"); 25 26 //在内存中创建一个长80，宽30的图片，默认黑色背景 27 //参数一：长 28 //参数二：宽 29 //参数三：颜色 30 int width = 80; 31 int height = 30; 32 BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); 33 34 //获取画笔 35 Graphics g = image.getGraphics(); 36 //设置画笔颜色为灰色 37 g.setColor(Color.GRAY); 38 //填充图片 39 g.fillRect(0,0, width,height); 40 41 //产生4个随机验证码，12Ey 42 String checkCode = getCheckCode(); 43 //将验证码放入HttpSession中 44 request.getSession().setAttribute("CHECKCODE_SERVER",checkCode); 45 46 //设置画笔颜色为黄色 47 g.setColor(Color.YELLOW); 48 //设置字体的小大 49 g.setFont(new Font("黑体",Font.BOLD,24)); 50 //向图片上写入验证码 51 g.drawString(checkCode,15,25); 52 53 //将内存中的图片输出到浏览器 54 //参数一：图片对象 55 //参数二：图片的格式，如PNG,JPG,GIF 56 //参数三：图片输出到哪里去 57 ImageIO.write(image,"PNG",response.getOutputStream()); 58 } 59 /** 60 * 产生4位随机字符串 61 */ 62 private String getCheckCode() { 63 String base = "0123456789ABCDEFGabcdefg"; 64 int size = base.length(); 65 Random r = new Random(); 66 StringBuffer sb = new StringBuffer(); 67 for(int i=1;i<=4;i++){ 68 //产生0到size-1的随机值 69 int index = r.nextInt(size); 70 //在base字符串中获取下标为index的字符 71 char c = base.charAt(index); 72 //将c放入到StringBuffer中去 73 sb.append(c); 74 } 75 return sb.toString(); 76 } 77 public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 78 this.doGet(request,response); 79 } 80 }
test.jsp
1 <%@ page contentType="text/html;charset=UTF-8" language="java" %> 2 <!DOCTYPE html> 3 <html lang="zh-CN"> 4 <head> 5 <meta charset="utf-8"/> 6 <title>登录</title> 7 <script type="text/javascript"> 8 function refreshCode() { 9 document.getElementById("vcode").src = "${pageContext.request.contextPath}/checkCodeServlet?time="+ new Date().getTime(); 10 } 11 </script> 12 </head> 13 <body> 14 15 <label for="vcode">验证码：</label> 16 <input type="text" name="verifycode" id="verifycode" placeholder="请输入验证码" style=" 120px;"/> 17 <a href="javascript:refreshCode()"> 18 <img src="${pageContext.request.contextPath}/checkCodeServlet" title="看不清点击刷新" id="vcode"/> 19 </a> 20 21 </body> 22 </html>