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From Dan Gross <dan.gr...@sun.com>
Subject Re: How to determing the relationship between tags
Date Wed, 05 Dec 2001 22:05:40 GMT
If you use an include directive, like:

<%@ include file="pageContainingTag2.jsp" %>

instead of a JSP include, then findAncestorWithClass() will work.

--Dan

Martin Cooper wrote:

>One thing to be aware of with findAncestorWithClass() is that it works only
>within the JSP page. This is not surprising in itself. However, if you want
>to be able to have the nested tag in an included page, you can't use this
>mechanism to find the parent.
>
>That is, with this code in the page:
>
>  <mytags:tag1 ... >
>      <mytags:tag2 ... />
>  </mytags:tag1>
>
>tag2 can find tag1 using findAncestorWithClass() just fine. However, with
>this:
>
>  <mytags:tag1 ... >
>      <jsp:include page="pageContainingTag2.jsp" />
>  </mytags:tag1>
>
>tag2 will be unable to find tag1 using findAncestorWithClass().
>
>It may not always be necessary to be able to do this, but I point it out
>because we had this issue with the Struts HTML tags. The various <html:*>
>tags need to refer to their containing <html:form> tag. However, if the form
>gets very large, and the page breaks the limit on the size of a compiled
>method, you are forced to split the form across pages. To make this work in
>Struts, the doStartTag() method in <html:form> stores a reference to itself
>as a request attribute, the nested tags use that, and then doEndTag() cleans
>it up.
>
>--
>Martin Cooper
>
>
>----- Original Message -----
>From: Shawn Bayern <bayern@essentially.net>
>To: Tag Libraries Users List <taglibs-user@jakarta.apache.org>;
><bo@groupserve.com>
>Sent: Wednesday, December 05, 2001 12:20 PM
>Subject: Re: How to determing the relationship between tags
>
>
>>On Wed, 5 Dec 2001, bo wrote:
>>
>>>I wonder if I can determine the relationship among tags, such as tag A
>>>should be within tag B etc. Is that possible? Thanks!
>>>
>>You can use a TagLibraryValidator class to enforce arbitrary
>>characteristics of the XML view of a JSP page, including specific
>>relationships among tags.  For an example of a SAX-based approach to
>>validation, see the JstlCoreTLV class in the "Standard" taglib.
>>
>>Tags can also, at runtime, gain access to their parent tag handlers.  The
>>most convenient mechanism for doing this is, in most cases, the static
>>TagSupport.findAncestorWithClass() method, part of the JSP API.
>>
>>Hope that helps,
>>
>>Shawn
>>
>>
>>--
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>
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>
>
>
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