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Four types of object scopes in JSPs

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Page: The current pages, that is, as long as the other pages are not valid, can be approximated to understand the Java this object

Request: A session, a simple understanding is the scope of a request is valid, for example, if the forward way to jump, the forward target page can still get the property value in request, for example, if the page jump by redirect way, The value in request disappears because redirect is equivalent to a re-issued request

Session: Browser process, as long as the current page is not closed (not forced by the browser to clear), regardless of how the jump is valid (also can be said to exist in a session cycle)

Application: Server, data is valid as long as the server is not restarted (not enforced by the program)

pagescope.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<%@ page import="java.util.*" %>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<body>

<%

Set data for two page ranges Key->value

Pagecontext.setattribute ("name", "Page_barry");

Pagecontext.setattribute ("Age", 21);

%>

<%

Take value

String Name= (String) pagecontext.getattribute ("name");

int age= (Integer) Pagecontext.getattribute ("Age");

%>

<font> Name: <%=name%></font>

<font> Age: <%=age%></font>

</body>

pagecontext01.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<%@ page import="java.util.*" %>

<%@ page errorpage="error.jsp" %>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<%

Pagecontext.setattribute ("NAME0", "PageInfo");

Request.setattribute ("Name1", "Requestinfo");

Session.setattribute ("Name2", "Sessioninfo");

Application.setattribute ("Name3", "ApplicationInfo");

Out.println ("Use pagecontext<br/>");

Out.println ("attribute value in page:" +pagecontext.getattribute ("NAME0") + "<br/>");

Out.println ("attribute value in Request:" +pagecontext.getrequest (). getattribute ("name1") + "<br/>");

Out.println ("attribute value in session:" +pagecontext.getsession (). getattribute ("name2") + "<br/>");

Out.println ("attribute value in Application:" +pagecontext.getservletcontext (). getattribute ("Name3") + "<br/>");

%>

</body>

pagescope_2.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<%@ page import="java.util.*" %>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<body>

<%

Set data for two page ranges Key->value

Pagecontext.setattribute ("name", "Page_barry");

Pagecontext.setattribute ("Age", 21);

%>

<jsp:forward page="pagetarget_2.jsp"></jsp:forward>

</body>

pagetarget_2.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<%@ page import="java.util.*" %>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<body>

<%

Take value

String Name= (String) pagecontext.getattribute ("name");

int age= (Integer) Pagecontext.getattribute ("Age");

%>

<font> Name: <%=name%></font>

<font> Age: <%=age%></font>

</body>

requestscope.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<%

Set data for two request ranges Key->value

Request.setattribute ("name", "Request_barry");

Request.setattribute ("Age", 12);

%>

<jsp:forward page="requesttarget.jsp"></jsp:forward>

</body>

requesttarget.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<%@ page import="java.util.*" %>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<%

Take value

String Name= (String) request.getattribute ("name");

int age= (Integer) Request.getattribute ("Age");

Get header information

Enumeration Enu=request.getheadernames ();

while (Enu.hasmoreelements ()) {

String Headername= (String) enu.nextelement ();

String Headervalue=request.getheader (headername);

%>

<%

}

%>

<font> name <%=name%></font><br>

<font> Age <%=age%></font>

</body>

requestscope_2.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<%

Set data for two request ranges Key->value

Request.setattribute ("name", "Request_barry");

Request.setattribute ("Age", 12);

%>

<%response.sendredirect ("requesttarget_2"); %>

</body>

requesttarget_2.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<%@ page import="java.util.*" %>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<%

Take value

String Name= (String) request.getattribute ("name");

int age= (Integer) Request.getattribute ("Age");

Get header information

Enumeration Enu=request.getheadernames ();

while (Enu.hasmoreelements ()) {

String Headername= (String) enu.nextelement ();

String Headervalue=request.getheader (headername);

%>

<%

}

%>

<font> name <%=name%></font><br>

<font> Age <%=age%></font>

</body>

sessionscope.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<%

Set the data for the two session range Key->value

Session.setattribute ("name", "Session_barry");

Session.setattribute ("Age", 12);

%>

The

</body>

sessiontarget.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<%

String Name= (String) session.getattribute ("name");

Integer age= (integer) Session.getattribute ("Age");

%>

<font> name <%=name%></font><br>

<font> Age <%=age%></font>

</body>

applicationscope.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<%

Set data for two application ranges Key->value

Application.setattribute ("name", "Application_barry");

Application.setattribute ("Age", 12);

%>

The

</body>

applicationtarget.jsp

<%@ page language="java" contenttype="text/html; Charset=utf-8 "

pageencoding="Utf-8"%>

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

<meta http-equiv="Content-type" content= "text/html; Charset=utf-8 ">

<title>insert title here</title>

<body>

<%

Take value

String Name= (String) application.getattribute ("name");

int age= (Integer) Application.getattribute ("Age");

%>

<font> name <%=name%></font><br>

<font> Age <%=age%></font>

</body>

Four types of object scopes in JSPs

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

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