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From commons-...@jakarta.apache.org
Subject [jira] Commented: (JELLY-85) TagScript doesn't clear its cached tags after run()
Date Sun, 12 Sep 2004 23:12:38 GMT
The following comment has been added to this issue:

     Author: Hans Gilde
    Created: Sun, 12 Sep 2004 4:11 PM
       Body:
Having looked at this some more, this TagScript should not clear its cache after run().

The cache reuses a Tag implementation between several runs of the same script, in the same
thread. It does not reuse the same Tag implementation multiple times within the same script.

The cache is a ThreadLocal object that is a member variable of TagScript. A seperate TagScript
object is always created for every instance of a tag encountered in an XML document. So, there
is no choice but to have a Tag implementation for every XML element in the document.

What the cache does do is ensure that the second time you run the script in the same thread,
it will not create a second set of Tag implementations.
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View this comment:
  http://issues.apache.org/jira/browse/JELLY-85?page=comments#action_53051

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View the issue:
  http://issues.apache.org/jira/browse/JELLY-85

Here is an overview of the issue:
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        Key: JELLY-85
    Summary: TagScript doesn't clear its cached tags after run()
       Type: Bug

     Status: Unassigned
   Priority: Major

    Project: jelly
 Components: 
             core / taglib.core
   Versions:
             1.0-beta-4

   Assignee: 
   Reporter: Scott Howlett

    Created: Tue, 16 Sep 2003 8:16 PM
    Updated: Sun, 12 Sep 2004 4:11 PM

Description:
TagScript caches the tags it generates in a ThreadLocal. At the beginning of run() it checks
to see if the context wants to cache tags - if not, it clears the cache and regenerates it.

But there is no corresponding check and cache clearing at the end of run(). So if a tag holds
onto some significant resource, that resource will hang around until the thread goes away
or until the tag is run again.

I am using Jelly Swing extensively, and various tags end up attached to the AWT Event thread
for the lifetime of my application.

As a quick fix, I have a patch that simply repeats the check-and-clear-cache behavior at the
end of TagScript.run(). I also have a patch that adds this behavior to StaticTagScript, whose
run() never seems to clear cached tags.

I am probably just unclear, but it seems to me that there is a deeper issue as well - the
context is being asked whether it wants to cache tags, but the result of this question affects
the TagScript, which is really independent of the context. It seems like if context wants
to cache tags, perhaps the ThreadLocal used for their storage ought to belong to the context
somehow.


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