完美的“咖啡豆”——JavaBean技术
为了简化JSP页面，提高Java程序代码的重用性及灵活性，可以在JSP中采用HTML与Java程序相分离的策略，将Java代码单独封装成一个处理某种业务逻辑的类。然后在JSP中调用此类，此类就是一个JavaBean组件。
下面，以登录界面的实现为例展示JavaBean的优势所在
上图是实现本次任务的Java Web工程结构图，其中Users.java中封装了用户名和密码两个属性，UsersDAO.java文件实现输入的登录名和密码的正确性判断。
而WEB-INF文件下的login.jsp搭建登录页面，dologin.jsp判断和处理登录信息，login_success.jsp为登录成功页面，login_failure.jsp为登录失败页面。
UsersDAO.java
package com.dao;
import com.po.Users;
//用户的业务逻辑类
public class UsersDAO {
//用户登录方法
public boolean usersLogin(Users u)
{
/*
* 如果用户名输入“小健”，密码输入“123456”则认为输入正确，返回true
* 否则，返回false
*/
if("小健".equals(u.getUsername())&&"123456".equals(u.getPassword()))
{
return true;
}
else
{
return false;
}
}
}
Users.java
package com.po;
//用户类
public class Users {
private String username;
private String password;
public Users()
{
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
login.jsp
<pre name="code" class="html"><%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <html> <head> <!-- Page title --> <title>登录界面</title> <!-- End of Page title --> <!-- Libraries --> <link type="text/css" href="css/login.css" rel="stylesheet" /> <link type="text/css" href="css/smoothness/jquery-ui-1.7.2.custom.html" rel="stylesheet" /> <script type="text/javascript" src="js/jquery-1.3.2.min.js"></script> <script type="text/javascript" src="js/easyTooltip.js"></script> <script type="text/javascript" src="js/jquery-ui-1.7.2.custom.min.js"></script> <!-- End of Libraries --> </head> <body> <div id="container"> <div class="logo"> <a href="#"><img src="images/logo.png" alt="" /></a> </div> <div id="box"> <form action="dologin.jsp" method="post"> <p class="main"> <label>用户名: </label> <input name="username" value="" /> <label>密码: </label> <input type="password" name="password" value=""> </p> <p class="space"> <input type="submit" value="登录" class="login" style="cursor: pointer;"/> </p> </form> </div> </div> </body> </html>
dologin.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
request.setCharacterEncoding("utf-8");
%>
<jsp:useBean id="loginUser" class="com.po.Users" scope="page"/>
<jsp:useBean id="userDAO" class="com.dao.UsersDAO" scope="page"/>
<jsp:setProperty property="*" name="loginUser"/>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
//如果用户和密码都正确，则userLogin()方法返回true，跳转到登陆成功页面，否则跳转到登录失败页面
if(userDAO.usersLogin(loginUser))
{
session.setAttribute("loginUser", loginUser.getUsername());
request.getRequestDispatcher("login_success.jsp").forward(request, response);
}
else
{
response.sendRedirect("login_failure.jsp");
}
%>
login_success.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<html>
<head>
<!-- Page title -->
<title>欢迎登录</title>
<!-- End of Page title -->
<!-- Libraries -->
<link type="text/css" href="css/login.css" rel="stylesheet" />
<link type="text/css" href="css/smoothness/jquery-ui-1.7.2.custom.html" rel="stylesheet" />
<script type="text/javascript" src="js/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="js/easyTooltip.js"></script>
<script type="text/javascript" src="js/jquery-ui-1.7.2.custom.min.js"></script>
<!-- End of Libraries -->
</head>
<body>
<div id="container">
<div class="logo">
<a href="#"><img src="images/8.jpg" alt="" /></a>
</div>
<div id="box">
<%
String loginUser = "";
if(session.getAttribute("loginUser")!=null)
{
loginUser = session.getAttribute("loginUser").toString();
}
%>
<br>
<br>
<Strong>欢迎您<font color="red"><%=loginUser%></font>,登录成功！</Strong>
</div>
</div>
</body>
</html>login_failure.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <html> <head> <!-- Page title --> <title>登录失败</title> <!-- End of Page title --> <!-- Libraries --> <link type="text/css" href="css/login.css" rel="stylesheet" /> <link type="text/css" href="css/smoothness/jquery-ui-1.7.2.custom.html" rel="stylesheet" /> <script type="text/javascript" src="js/jquery-1.3.2.min.js"></script> <script type="text/javascript" src="js/easyTooltip.js"></script> <script type="text/javascript" src="js/jquery-ui-1.7.2.custom.min.js"></script> <!-- End of Libraries --> </head> <body> <div id="container"> <div class="logo"> <a href="#"><img src="images/9.jpg" alt="" /></a> </div> <br> <div id="box"><strong> 登录失败！请检查用户或者密码!<br><br> <a href="login.jsp">返回登录</strong></a> </div> </div> </body> </html>
任务效果
