1.login.jsp

<%@ 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%>">
    
    <title>My JSP 'index.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
    <style type="text/css">
    body{font-size:16px;}
    </style>
    <script type="text/javascript">
    function mycheck(){
    if(form1.userName.value==""){
    alert("用户名不能为空，请输入用户名");
    form1.userName.focuse();
    return;
    }
    if(form1.password.value==""){
    alert("密码不能为空，请输入密码");
    form1.password.focus();
    return;
    }
    if(form1.validationCode.value==""){
    alert("验证码不能为空，请输入验证码");
    form1.validationCode.focus();
    return;
    }
    if(form1.validationCode.value!=form1.validationCode1.value){
    alert("请输入正确的验证码");
    form1.validationCode.focus();
    return;
    }
    form1.submit1();
    }
    </script>
  </head>
  
  <body bgcolor="pink">
   <form action="loginCheck.jsp" name="form1" method="post">
   用户名：<input type="text" name="userName" size="24"><br>
   密&nbsp;&nbsp;&nbsp;&nbsp;码：<input type="password" name="password" size="24"><br>
   验证码：<input type="text" name="validationCode" onKeyDown="if(event.keyCode==13){form1.submit.focus();}"size="4">
  <%
  int intmethod1=(int)((((Math.random())*5))+1);
  int intmethod2=(int)((((Math.random())*5))+1);
  int intmethod3=(int)((((Math.random())*5))+1);
  int intmethod4=(int)((((Math.random())*5))+1);
  
  String intsum=intmethod1+""+intmethod2+intmethod3+intmethod4;
   %> 
   <input type="hidden" name="validationCode1" value="<%=intsum%>">
   <img style="height:20px;weight:20px" src="<%=intmethod1 %>.png">
   <img style="height:20px;weight:20px" src="<%=intmethod2 %>.png">
   <img style="height:20px;weight:20px" src="<%=intmethod3 %>.png">
   <img style="height:20px;weight:20px" src="<%=intmethod4 %>.png">
   <br>
   <br>
   <input type="submit" name="submit1" value="登录" onClick="mycheck()">
   &nbsp;
   <input type="reset" value="重置">
   </form>
    
     <br>
  </body>
</html>

2.loginCheck.jsp

<%@ 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%>">
    
    <title>My JSP 'index.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
    
  </head>
  
  <body  bgcolor="pink">
  <%
  request.setCharacterEncoding("utf-8");
  String name=request.getParameter("userName");
  String password=request.getParameter("password");
  if(request.getParameter("validationCode1").equals(request.getParameter("validationCode"))){
  if(name.equals("xiaojunzi")&&(password.equals("123456"))){
  session.setAttribute("userName", name);
  response.sendRedirect("main.jsp");
  }else{
  response.sendRedirect("login.jsp");
  }
  }else{
  response.sendRedirect("login.jsp");
  }
   %>

     <br>
  </body>
</html>

3.main.jsp

<%@ 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%>">
    
    <title>My JSP 'index.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
    
  </head>
  
  <body  bgcolor="pink">
  <%
 String name=(String)session.getAttribute("userName");
   %>
您好<%=name %>,欢迎您访问<br>
<a href="exit.jsp">【退出系统】</a>
     <br>
  </body>
</html>

exit.jsp

<%@ 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%>">
    
    <title>My JSP 'index.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
    
  </head>
  
  <body>
  <%
session.invalidate();
response.sendRedirect("login.jsp");
   %>
     <br>
  </body>
</html>

5.图片