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https://issues.apache.org/jira/browse/SLING-3423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13922236#comment-13922236
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Julian Sedding commented on SLING-3423:
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[~bdelacretaz], I believe that there is a desire to merge arbitrary resources.
The current implementation only merges resources based on the search-paths,
which only covers the "overlay" use-case. IIUC Alex is interested in merging
based on the resource-type hierarchy, which would be a different (but equally
valid) use-case.
It would be nice to find a way to re-use the same merge-logic for both (and
possibly even more) use-cases. This would cut down the implementation effort,
as well as promote consistency.
One approach to make this logic useful is by introducing a utility (either
static or a service). Carsten fears that merging resource-trees via a utility
generates "trees" that are dangling in mid-air (i.e. they are not accessible
via the resource resolver, because they are generated ad-hoc).
The approach I propose in my previous comment leaves the resources in the
resource-tree (i.e. accessible via the resource resolver). However, following
the "don't call us we'll call you" design pattern, I propose an extension point
that allows Alex to inject the resources he wants merged into the
resource-provider implementation, thus achieving re-use of the merge logic.
> ResourceMergerService API must allow custom merge paths
> -------------------------------------------------------
>
> Key: SLING-3423
> URL: https://issues.apache.org/jira/browse/SLING-3423
> Project: Sling
> Issue Type: Bug
> Components: Extensions
> Affects Versions: Resource Merger 1.0.0
> Reporter: Alexander Klimetschek
>
> From http://sling.markmail.org/thread/3wt33wniwgflmk27
> The ResourceMergerService added by SLING-2986 must have this one central API,
> where the caller = application defines the merge paths!
> Resource merge(ResourceResolver resolver, String mergeRootPath, String
> relativePath, String... mergePaths)
> Example values for the use case of the overlay resource provider:
> resolver = based on the current request (user)
> mergeRootPath = /mnt/overlay
> relativePath = <dynamic part>, for example: "projectX/content/ui/toolbar"
> mergePaths = /apps, /libs
> This was in the original patch [1], sadly removed and later added back but
> completely missing the point.
> Currently it is all tied to the sling search path internally, but this would
> just be ONE of different options the application might want to chose for it.
> The specific /mnt/overlay ResourcerProvider would take the sling search path
> and expose resources based on calling the merger service with this as the
> mergePaths. (Currently there is a single implementation
> MergedResourceProviderFactory for both ResourceMergerService and the
> ResourceProvider service).
> This is simply a proper separation of concerns.
> Another application with different merge paths would be to merge resource
> type hierarchies: use the resource type and its super types. This could allow
> one to put UI dialogs in the resource types (say at ./dialog) and then be
> able to extend dialogs in sub resource types using the merger service.
> [1]
> https://github.com/gknob/sling-resourcemerger/commit/a3e1b78c87e54cd5c32a58627a4de0420229e1f9
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