Detailed explanation of the four scopes in JavaBean
This article mainly introduces the relevant information on the detailed explanation of the four scopes of JavaBean. I hope this article can help everyone. Friends in need can refer to the following
The four scopes of JavaBean Detailed explanation
One explanation
The scope attribute of useBeans can be used to specify the scope of javabean.
Two or four scopes
Three codes
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><%@ 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>Four test results
The above is the detailed content of Detailed explanation of the four scopes in JavaBean. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1378
52
Usage of typedef struct in c language
May 09, 2024 am 10:15 AM
typedef struct is used in C language to create structure type aliases to simplify the use of structures. It aliases a new data type to an existing structure by specifying the structure alias. Benefits include enhanced readability, code reuse, and type checking. Note: The structure must be defined before using an alias. The alias must be unique in the program and only valid within the scope in which it is declared.
How to solve variable expected in java
May 07, 2024 am 02:48 AM
Variable expected value exceptions in Java can be solved by: initializing variables; using default values; using null values; using checks and assignments; and knowing the scope of local variables.
Advantages and disadvantages of closures in js
May 10, 2024 am 04:39 AM
Advantages of JavaScript closures include maintaining variable scope, enabling modular code, deferred execution, and event handling; disadvantages include memory leaks, increased complexity, performance overhead, and scope chain effects.
What does include mean in c++
May 09, 2024 am 01:45 AM
The #include preprocessor directive in C++ inserts the contents of an external source file into the current source file, copying its contents to the corresponding location in the current source file. Mainly used to include header files that contain declarations needed in the code, such as #include <iostream> to include standard input/output functions.
C++ smart pointers: a comprehensive analysis of their life cycle
May 09, 2024 am 11:06 AM
Life cycle of C++ smart pointers: Creation: Smart pointers are created when memory is allocated. Ownership transfer: Transfer ownership through a move operation. Release: Memory is released when a smart pointer goes out of scope or is explicitly released. Object destruction: When the pointed object is destroyed, the smart pointer becomes an invalid pointer.
Can the definition and call of functions in C++ be nested?
May 06, 2024 pm 06:36 PM
Can. C++ allows nested function definitions and calls. External functions can define built-in functions, and internal functions can be called directly within the scope. Nested functions enhance encapsulation, reusability, and scope control. However, internal functions cannot directly access local variables of external functions, and the return value type must be consistent with the external function declaration. Internal functions cannot be self-recursive.
There are several situations where this in js points to
May 06, 2024 pm 02:03 PM
In JavaScript, the pointing types of this include: 1. Global object; 2. Function call; 3. Constructor call; 4. Event handler; 5. Arrow function (inheriting outer this). Additionally, you can explicitly set what this points to using the bind(), call(), and apply() methods.
The difference between let and var in vue
May 08, 2024 pm 04:21 PM
In Vue, there is a difference in scope when declaring variables between let and var: Scope: var has global scope and let has block-level scope. Block-level scope: var does not create a block-level scope, let creates a block-level scope. Redeclaration: var allows redeclaration of variables in the same scope, let does not.
