JavaBean四个作用域范围的详解
一 说明
使用useBeans的scope属性可以用来指定javabean的作用范围。
二 四个作用范围
三 代码
1、login.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+"/";%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" rel="external nofollow" > <title>My JSP 'login.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" rel="external nofollow" rel="external nofollow" rel="external nofollow" > --> </head> <body> <h1>系统登录</h1> <hr> <form name="loginForm" action="dologin.jsp?mypass=999999" method="post"> <table> <tr> <td>用户名：</td> <td><input type="text" name="username" value=""/></td> </tr> <tr> <td>密码：</td> <td><input type="password" name="password" value=""/></td> </tr> <tr> <td colspan="2" align="center"><input type="submit" value="登录"/></td> </tr> </table> </form> </body></html>
2、dologin.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+"/";%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" rel="external nofollow" > <title>My JSP 'dologin.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" rel="external nofollow" rel="external nofollow" rel="external nofollow" > --> </head> <body> <jsp:useBean id="myUsers" class="com.po.Users" scope="page"/> <h1>setProperty动作元素</h1> <hr> <!--根据表单自动匹配所有的属性 --> <%-- <jsp:setProperty name="myUsers" property="*"/> --%> <!--根据表单匹配所有部分的属性 --> <%-- <jsp:setProperty name="myUsers" property="username"/> --%> <!--根表单无关，通过手工赋值给属性 --> <%-- <jsp:setProperty name="myUsers" property="username" value="lisi"/> <jsp:setProperty name="myUsers" property="password" value="888888"/> --%> <!--通过URL传参数给属性赋值 --> <jsp:setProperty name="myUsers" property="username"/> <jsp:setProperty name="myUsers" property="password" param="mypass"/> <!-- 使用传统的表达式方式来获取用户名和密码 --> <%-- 用户名：<%=myUsers.getUsername() %><br> 密码：<%=myUsers.getPassword() %><br> --%> <!-- 使用getProperty方式来获取用户名和密码 --> 用户名：<jsp:getProperty name="myUsers" property="username"/> <br> 密码：<jsp:getProperty name="myUsers" property="password"/><br> <br> <br> <a href="testScope.jsp" rel="external nofollow" >测试javabean的四个作用域范围</a> <% request.getRequestDispatcher("testScope.jsp").forward(request, response); %> </body></html>
3、testScope.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%><%@ page import="com.po.Users"%><% 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" rel="external nofollow" rel="external nofollow" > <title>My JSP 'testScope.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" rel="external nofollow" rel="external nofollow" rel="external nofollow" > --> </head> <body> <h1>Javabean的四个作用域范围</h1> <hr> <jsp:useBean id="myUsers" class="com.po.Users" scope="page" /> 用户名：<jsp:getProperty name="myUsers" property="username" /><br> 密码：<jsp:getProperty name="myUsers" property="password" /><br> <!-- 使用内置对象获取用户名和密码 --> <hr> <%-- 用户名：<%=((Users)application.getAttribute("myUsers")).getUsername()%><br> 密码：<%=((Users)application.getAttribute("myUsers")).getPassword() %><br> --%> <%-- 用户名：<%=((Users)session.getAttribute("myUsers")).getUsername()%><br> 密码：<%=((Users)session.getAttribute("myUsers")).getPassword() %><br> --%> <%-- 用户名：<%=((Users)request.getAttribute("myUsers")).getUsername()%><br> 密码：<%=((Users)request.getAttribute("myUsers")).getPassword() %><br> --%> <% String username = ""; String password = ""; if (pageContext.getAttribute("myUsers") != null) { username = ((Users) pageContext.getAttribute("myUsers")) .getUsername(); password = ((Users) pageContext.getAttribute("myUsers")) .getPassword(); } %> 用户名：<%=username%><br> 密码：<%=password%><br> </body></html>
四 测试结果
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