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java中登陆时的验证码(jcaptcha)

java.jcaptcha 
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<%@ page language="java" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    
    <title>我的jsp项目</title>
    <script type="text/javascript" src="http://lib.sinaapp.com/js/jquery/1.7.2/jquery.min.js"></script>
    <style type="text/css">
    	span{
    		color:red;
    	}
    </style>
  </head>
  
  <body>
  	<c:choose>
  		<c:when test="${param.code == '10001'}">
  			<div style="color:red">用户名或密码错误</div>
  		</c:when>
  		<c:when test="${param.code == '10003' }">
  			<div style="color:red">验证码错误</div>
  		</c:when>
  		<c:otherwise>
  			xxxx
  		</c:otherwise>
  	</c:choose>
 	
  	<form action="login.jspx" method="post" id="myform">
  		UserName: <input type="text" name="username"/><span id="name_error"></span> <br/>
  		Password: <input type="password" name="password"/><span id="pwd_error"></span> <br/>
  		验证码:<input type="text" name="captcha"/>
  		<a href="javascript:;" if="changeVailidata"> <img src="jcaptcha.jpg" id="jcaptcha"></a>
  		<input type="submit" value="Login" id="btn"/>
  	</form>
  	
  
  	<script type="text/javascript">
  		$(document).ready(function(){
  		
  		$("#changeVailidata").click(funcition()){
  			$("#jcaptchar").attr("src","jcaptcha.jpg");
  		})
  			$("#btn").click(function(){
  				var name = $("input[name='username']").val();
  				var pwd = $("input[name='password']").val();
  				if(name.trim() == "") {
  					$("#name_error").html("请输入用户名");
  					return;
  				}
  				if(pwd == "") {
  					$("#pwd_error").html("请输入密码");
  					return;
  				}
  				$("#myform").submit();
  				
  			});
  			
  		});
  	
  	</script>
  </body>
</html>


 这里写的验证码用的是jcaptcha插件；到网上可以下载到他的jar包；


 


 以上是验证码配合登陆时，在jsp中的写法；


下面是当在servlet中接受验证码：


 


public class LoginServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		String captcha = request.getParameter("captcha");//接受jsp中传过来的验证码；
                //这里必须这么写才能生成验证码；jcaptcha的官网里面有详细的介绍;
		if (SimpleImageCaptchaServlet.validateResponse(request, captcha)) {
			String name = request.getParameter("username");
			String pwd = request.getParameter("password");
			//服务端的验证
			if(name == null || pwd == null) {
				response.sendRedirect("index.jsp");
				return;
			}

			System.out.println("Name:" + name + "\tpwd:" + pwd);
			
			//2.验证用户名和密码是否正确
			UserDao dao = new UserDao();
			User user = dao.findByNameAndPwd(name, pwd);
			if(user != null) {				
				
				//Servlet中获取session
				HttpSession session = request.getSession();
				
				session.setAttribute(Const.USER_IN_SESSION, user);
				response.sendRedirect("prod.jspx");// 登陆成功，重定向跳转到prod.jspx;
			} else {
				response.sendRedirect("index.jspx?code=10001");
			}
		}else {
			response.sendRedirect("index.jspx?code=10003");
		}
	}

}


  


  

    
    
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