Problems with page maps stored in session
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Key: WICKET-3108
URL: https://issues.apache.org/jira/browse/WICKET-3108
Project: Wicket
Issue Type: Bug
Affects Versions: 1.4.12
Reporter: Jeremy Thomerson
Assignee: Jeremy Thomerson
Priority: Minor
A client engaged me to assist in fixing multiple problems they found while
writing a custom page map eviction strategy for page maps that have not been
accessed in a while. Digging into the first problem revealed a few others.
I'd like someone who is more familiar than me with the session and page map
stuff to review this before I commit it. The quick start attached demonstrates
the problems. I have yet to write test cases that can be added to the suite to
replicate these issues.
PROBLEM 1:
If you call IPageMap.remove(), the page map is not actually removed because
it's in the dirty objects list, which means that it gets set back on the
session in the requestDetached() method. The quickstart demonstrates this in a
link for ease of demonstration, but in reality, it applies even if someone is
doing custom page map eviction in their request cycle somewhere.
PROBLEM 2:
It seems to be a safe assumption that every page map that is used in the
session should also be in usedPageMaps, and that this map should always be
exactly in sync with what's actually in your session (as attributes). Right
now, they are not in sync. First, the default page map was not added to
usedPageMaps in the dirtyPageMap(IPageMap) method. Second, when page maps are
created, they are not dirtied (which means they are not in the usedPageMaps
collection), although they are set as attributes on the session immediately.
This causes a problem in the newPageMap(String) method with actually adhering
to the max number you set.
PROBLEM 3:
If you have a bunch of popup links on a page, they can create more page maps
than are allowed, and the number of page maps stored in the session grows
beyond the limit of what you've specified. The real unanswered question I have
is this: must we really create the page map when the link is first rendered?
Or could we wait until it is clicked?
NOTE: the fix for problems 2 and 3 relies on the fix for problem 1 being
committed, because the call to pm.remove() in newPageMap(IPageMap) will not
work without the fix for problem 1
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