基于ajax实现验证码功能

来源：宝玛科技网

本文实例为大家分享了ajax实现验证码功能的具体代码，供大家参考，具体内容如下

首先创建一个验证码：

<%@ page contentType="image/jpeg; charset=utf-8" 
 language="java" import="java.util.*,java.awt.*,java.awt.image.*,javax.imageio.*" 
 pageEncoding="UTF-8"%> 
<!-- 以上导入awt和awt.image包 --> 
<%! 
 //获取随机颜色 
 public Color getColor(){ 
 Random random = new Random(); 
 //使用rgb()随机产生颜色 
 int r = random.nextInt(256); 
 int g = random.nextInt(256); 
 int b = random.nextInt(256); 
 
 return new Color(r,g,b); 
 } 
 
 //获取随机数字 产生一个4位数 
 public String getNum(){ 
 String str = ""; 
 Random random = new Random(); 
 for(int i = 0;i < 4;i++){ 
 str += random.nextInt(10); //0-9 
 } 
 return str; 
 } 
%> 
 
<% 
 /* 清除缓存 */ 
 response.setHeader("pragma", "mo-cache"); 
 response.setHeader("cache-control", "no-cache"); 
 response.setDateHeader("expires", 0); 
 //产生矩形框 
 BufferedImage image = new BufferedImage(80,30,BufferedImage.TYPE_INT_RGB); 
 //获取画笔工具 
 Graphics g = image.getGraphics(); 
 //设置矩形框的颜色 
 g.setColor(new Color(200,200,200)); 
 //设置坐标和宽高 
 g.fillRect(0, 0, 80, 30); 
 
 //随机产生干扰线 
 for(int i = 0;i < 30;i++){ 
 Random random = new Random(); 
 int x = random.nextInt(80); 
 int y = random.nextInt(30); 
 int x1 = random.nextInt(x + 10); 
 int y1 = random.nextInt(y + 10); 
 //设置随机颜色 
 g.setColor(getColor()); 
 //画出来 
 g.drawLine(x, y, x1, y1); 
 } 
 
 //字的颜色和数字 
 g.setFont(new Font("Microsoft YaHei",Font.BOLD,16)); 
 g.setColor(Color.BLACK); 
 //获取随机数字 
 String checkNum = getNum(); 
 
 //给字拼接空格 
 StringBuffer sb = new StringBuffer(); 
 for(int i = 0;i < checkNum.length();i++){ 
 sb.append(checkNum.charAt(i) + " "); 
 } 
 //画出数字 
 g.drawString(sb.toString(), 15, 20); 
 //存入session域中 
 session.setAttribute("CHECKNUM", checkNum); //例如1010 
 //将图像以jpeg的形式通过字节流

输出 ImageIO.write(image, "jpeg", response.getOutputStream()); //清除缓存 out.clear(); //放入body中 out = pageContext.pushBody(); %>

将验证码压缩成图片，在checkcode.jsp中引用,并在该页面中利用ajax向服务器发送数据

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> 
<% 
String path = request.getContextPath(); 
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 
%> 
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<html> 
 <head> 
 <base href="<%=basePath%>" rel="external nofollow" > 
 
 <title>验证码</title> 
 
 <meta http-equiv="pragma" content="no-cache"> 
 <meta http-equiv="cache-control" content="no-cache"> 
 <meta http-equiv="expires" content="0"> 
 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 
 <meta http-equiv="description" content="This is my page"> 
 <style type="text/css"> 
 table{ 
 margin: 100px auto; 
 } 
 
 </style> 
 </head> 
 
 <body> 
 <table border="0" align="center"> 
 <tr> 
 <td>验证码</td> 
 <td><input type="text" name="checkcode" id="checkcodeID" maxlength="4" size="4"></td> 
 <td><img 加载失败" src="image.jsp"></td> 
 <td id="show">√√√</td> 
 </tr> 
 </table> 
 </body> 
 <script type="text/javascript"> 
 //去除空格 
 function trim(str){ 
 //从左侧开始替换空格 
 str = str.replace(/^\s*/,""); 
 //从左侧开始替换空格 
 str = str.replace(/\s$/,""); 
 return str; 
 } 
 
 </script> 
 
 <script type="text/javascript"> 
 //创建ajax对象 
 function createAjax(){ 
 var ajax = null; 
 try{ 
 ajax = new ActiveXObject("microsoft.xmlhttp"); 
 }catch(e){ 
 try{ 
 ajax = new XMLHttpRequest(); 
 }catch(e1){ 
 alert("请更换浏览器"); 
 } 
 } 
 return ajax; 
 } 
 </script> 
 
 
 <script type="text/javascript"> 
 document.getElementById("checkcodeID").onkeyup = function(){ 
 var checkcode = this.value; 
 //去除空格 
 checkcode = trim(checkcode); 
 if(checkcode.length == 4){ 
 //获取ajax对象 
 var ajax = createAjax(); 
 //获取去空格的内容 
 
 var method = "POST"; 
 var url = "${pageContext.request.contextPath}/CheckcodeServlet?time="+new Date().getTime(); 
 //准备发送异步请求 
 ajax.open(method, url); 
 //设置请求头POST提交方式才需要 
 ajax.setRequestHeader("content-type", "application/x-www-form-urlencoded"); 
 //拼接实体内容 
 var content = "checkcode=" + checkcode; 
 //发送请求 
 ajax.send(content); 
 
 //监听服务器状态变化 
 ajax.onreadystatechange = function(){ 
 if(ajax.readyState == 4){ 
 if(ajax.status == 200){ 
 //获取服务器内容 
 var tip = ajax.responseText; 
 //获取图片路径 然后进行放入td中 
 var img = document.createElement("img"); 
 img.src = tip; 
 img.style.width = "14px"; 
 img.style.height = "14px"; 
 var td = document.getElementById("show"); 
 td.innerHTML = ""; 
 td.appendChild(img); 
 } 
 } 
 } 
 
 } 
 
 } 
 </script> 
</html>

然后编写服务端,接收输入的信息，判断是否与验证码相互匹配,将对应的图片的路径以输出流的方式输出

public class CheckcodeServlet extends HttpServlet { 
 @Override 
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) 
 throws ServletException, IOException { 
 req.setCharacterEncoding("utf-8"); 
 resp.setContentType("text/html;charset=utf-8"); 
 //图片路径 
 String tip = "images/MsgError.gif"; 
 
 String checkcode = req.getParameter("checkcode"); 
 //测试 
 System.out.println(checkcode); 
 //获取session域中的数字 
 String checkcodeService = (String) req.getSession().getAttribute("CHECKNUM"); 
 //判断 
 if (checkcode.equals(checkcodeService)) { 
 tip = "images/MsgSent.gif"; 
 } 
 //

输出路径 PrintWriter pw = resp.getWriter(); pw.write(tip); pw.flush(); pw.close(); } }

当输入第4个数字的时候就会出现提示
运行结果: