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Web Component Certification (OCEJWCD)

JSTL: remove object from scope

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posted 17 years ago

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Hi,

I have four objects in four different scopes
[page,request,session,application].

And I use:
<c:remove var="popy"/>

In the absence of the scope attribute it removes the objects from all the
four scopes.

If it is required to remove the object from the session
scope won't <c:remove var="popy"/> be correct answer too, because it
starts from page and goes on goes on, finding and removing objects of that
name from the scopes?

Please confirm this!

Thanks,

cmbhatt

khushhal yadav

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Posts: 242

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posted 17 years ago

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No Chandra

Because the requirement is to remove it from session.
Not from all the scopes.

Just imagine of the havoc, it can create in a running application.
If by mistake
instead of writing <c:remove var="popy" scope="session"/>
you write <c:remove var="popy"/>

Objects in the other scopes might being used somewhere else in the application.

So it always better to be specific.

And in exam, I think it will depend on the number of options to be choosen.

Regards,
Khushhal

rgrds,
Khushhal

Chandra Bhatt

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posted 17 years ago

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Thanks khushhal,

Yeah it is was I was looking for! It would depend on how many options
we have to choose, but we should be very specific. Alright!

Thanks,

cmbhatt

Srinivasan thoyyeti

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posted 17 years ago

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Chandra,

You are absolutely correct.

Given options
1. <c:remove var="poppy"/>
2. <c:remove var="poppy" scope=session/>

if (asked to select one which will delete poppy from session only) {
then choose 2.
}
else{
if (asked to select two from following which can delete poppy from session) then choose 1,2.
}
[ August 14, 2007: Message edited by: Srinivasan thoyyeti ]

Thanks & Regards, T.Srinivasan
SCWCD 1.4(89%), SCJP 5.0(75%)

Chandra Bhatt

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posted 17 years ago

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Yeah Srinivasan,

That would be right way to handle with that sort of question.

Your wise description made it more clear!

Thanks,
[ August 14, 2007: Message edited by: Chandra Bhatt ]

cmbhatt

Michael Ku

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posted 17 years ago

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Chandra, thank you for your post that pointed out the in the absence of a scope attribute in the <c:remove> tag, the scope is all scopes. On page 448 pf HFSJ it says that the default scope is page. I missed the correction in the errata of the book

{448} 2nd handwritten comment;
The scope is optional, and like always - page is the default scope.
should be:
The scope is optional, and when not specified the attribute is removed from all scopes.

In appreciation of your post, I have written a JSP that points out what you wrote. Here it is

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
 
<HTML>
<HEAD>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
 
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 
<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<META name="GENERATOR" content="IBM Software Development Platform">
<META http-equiv="Content-Style-Type" content="text/css">
<LINK href="theme/Master.css" rel="stylesheet"
type="text/css">
<TITLE>Remove Tag Test</TITLE>
</HEAD>
<BODY>
 
 setting String object into all 4 scopes using same key name 
<c:set var="popy" value=" I am in page scope"></c:set>
<c:set var="popy" scope="request" value=" I am in request scope"></c:set>
<c:set var="popy" scope="session" value=" I am in session scope"></c:set>
<c:set var="popy" scope="application" value=" I am in appliation scope"></c:set>
 
 Where am I? ${popy}
<c:if test="${empty popy}" >popy is nowhere to be found</c:if>
 
 Removing popy from page scope
<c:remove var="popy" scope="page"/>
 
 Where am I? ${popy}
<c:if test="${empty popy}" >popy is nowhere to be found</c:if>
 
 Removing popy from request scope
<c:remove var="popy" scope="request"/>
 
 Where am I? ${popy}
<c:if test="${empty popy}" >popy is nowhere to be found</c:if>
 Removing popy from session scope
<c:remove var="popy" scope="session"/>
 
 Where am I? ${popy}
<c:if test="${empty popy}" >popy is nowhere to be found</c:if>
 Removing popy from application scope
<c:remove var="popy" scope="application"/>
 
 
 Where am I? ${popy}
<c:if test="${empty popy}" >popy is nowhere to be found</c:if>
 starting over... 
 setting String object into all 4 scopes using same key name 
<c:set var="popy" value=" I am in page scope"></c:set>
<c:set var="popy" scope="request" value=" I am in request scope"></c:set>
<c:set var="popy" scope="session" value=" I am in session scope"></c:set>
<c:set var="popy" scope="application" value=" I am in appliation scope"></c:set>
 
 Where am I? ${popy}
<c:if test="${empty popy}" >popy is nowhere to be found</c:if>
 
 Removing popy from page scope
<c:remove var="popy" scope="page"/>
 
 Where am I? ${popy}
<c:if test="${empty popy}" >popy is nowhere to be found</c:if>
 Removing popy again without using a scope
<c:remove var="popy" />
 
 Where am I? ${popy}
 
<c:if test="${empty popy}" >popy is nowhere to be found</c:if>

</BODY>
</HTML>

Once again, thanks

Chandra Bhatt

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Posts: 1710

posted 17 years ago

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Thank you Michael,

I appreciate you!

cmbhatt

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