JSP对属性的操作

Bertha 。 2022-06-08 10:24 166阅读 0赞

属性操作相关方法：

Object getAttribute(String name) ;

Enumeration getAttributeNames() ;

void removeAttribute(String name) ;

void setAttribute(String name, Object o)

pageContext,request,session,application  对象都有这些方法。这四个对象也称为域对象。

pageContext ：属性的作用范围仅限于当前JSP页面

request：属性的作用范围仅限于同一个请求

session：属性的作用范围限于一次会话（浏览器打开直到关闭，称为一次会话）

application：属性的作用范围限于当前WEB应用。只要在一处设置属性，其他各处都可以获取到。

测试：

index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
 <%
 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>page1</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">
 	
 </head>
 
 <body>
 <%request.setAttribute("name", "sasa");
 application.setAttribute("addr", "beijing");
 pageContext.setAttribute("gender", "man");
 session.setAttribute("age", "18");
 %>
 
 request:<%=request.getAttribute("name") %>
 
 application:<%=application.getAttribute("addr") %>
 
 pageContext:<%=pageContext.getAttribute("gender") %>
 
 session:<%=session.getAttribute("age") %>
 
 <a href="/MyLab2/index2.jsp">index2</a>
 <a href="index3">index3</a>
 </body>
 </html>

index2.jsp

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
 <%
 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>page2</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">
 	
 </head>
 
 <body>
 <%--request.setAttribute("name", "sasa");
 application.setAttribute("addr", "beijing");
 pageContext.setAttribute("gender", "man");
 session.setAttribute("age", "18");
 --%>
 
 request:<%=request.getAttribute("name") %>
 
 application:<%=application.getAttribute("addr") %>
 
 pageContext:<%=pageContext.getAttribute("gender") %>
 
 session:<%=session.getAttribute("age") %>
 
 
 </body>
 </html>

index3Servlet:

package com.sa.servlet;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import javax.websocket.Session;
    
    import org.apache.catalina.core.ApplicationContext;
    
    public class Index3Servlet extends HttpServlet {
       @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    		throws ServletException, IOException {
    	// TODO Auto-generated method stub
    	//1. 在servlet中无法获得pageContext对象
    	   PrintWriter out=resp.getWriter();  
    	   String name=(String) req.getAttribute("name");
    	   out.println("name:"+name);
    	   String addr=(String) getServletContext().getAttribute("addr");
    	   out.println("addr:"+addr);
    	   HttpSession session=req.getSession();
    	   String age= (String) session.getAttribute("age");
    	   out.println("age"+age);
    }
    }

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[Center]: /images/20220608/0368996e389d48f19f7aab50b60d5fb3.png
[Center 1]: /images/20220608/a2ca637ea20c4541aa9181bd7f86e02a.png
[Center 2]: /images/20220608/ec3e05ca23f84811b45b2e98300e1c9e.png