MarkupCache messed up when using MergedMarkup (e.g. for Page markup
inheritance) together with IResourceStreams that do NOT also implement
IFixedLocationResourceStream
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Key: WICKET-2764
URL: https://issues.apache.org/jira/browse/WICKET-2764
Project: Wicket
Issue Type: Bug
Components: wicket
Affects Versions: 1.4.6
Reporter: Christian Oldiges
Priority: Minor
For a project that requires markup reloading and a custom markup directory
structure we have implemented a custom IResourceStreamLocator.
This implementation creates instance of its own IResourceStream implementation
which does NOT at the same time implement IFixedLocationResourceStream.
This means there is no "locationAsString()" method implemented on the resource
stream instances.
Now the MarkupCache comes into the picture. It is using a cacheKey and the
locationAsString as cache keys using a 2 step mechanism.
cacheKey -> locationAsString
locationAsString -> Markup
Additionally MergedMarkup comes into play. MergedMarkup is a markup instance
that merges a base markup with another markup.
This is typically used for markup inheritance.
BasePage.html implemented by BasePage
PageA.html extends BasePage
PageB.html extends BasePage
MergedMarkup#locationAsString() concatenates the locationAsString values of its
source markup/resource objects putting a ":" inbetween.
This means it will NEVER be NULL, even if both source objects return NULL as
their locationAsString values.
Now, in case the original resource streams do not implement
IFixedLocationResourceStream, this result in a locationAsString of "null:null".
Unfortunately this is the case for ALL possible combinations of the source
objects of MergedMarkup
So the locationAsString is "null:null" for (BasePage,PageA) and also for
(BasePage,PageB)
Back to the MarkupCache#loadMarkup method.
There is a check to use the cacheKey as a replacement for locationAsString in
case its NULL.
Now, if the Markup loaded is a MergedMarkup instance, it doesnt return NULL,
but "null:null".
So, putIntoCache() gets called with "null:null" as the key for ALL possible
combinations resulting in a huge chaos of templates being merged together, when
those cache entries are used later on.
A workaround is to implement IFixedLocationResourceStream on our custom
IResourceStream implementation.
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