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From "Brett Birschbach (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SLING-8279) Having a Resource + ResourceMetadata should be sufficient for roundtrip link mapping.
Date Tue, 19 Feb 2019 14:27:04 GMT

    [ https://issues.apache.org/jira/browse/SLING-8279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16771962#comment-16771962
] 

Brett Birschbach commented on SLING-8279:
-----------------------------------------

Though we could debate the merits of where code should live and probably never come to an
agreement...

Here's my opinion, in agreement with Mark.

1) The option to construct a URL in a model is already possible since the `request` is available
- this is just making it more streamlined

2) The `requestResolver.map(resource)` and other similar functions that take a resource give
a potentially unexpected behavior of ignoring the current request (since the resource conceivably
is tied to the request, per Mark's notes) - requiring a developer to explicitly pass `null`
in the case that they *actually* want the function to be evaluated outside the context of
a request seems like a better coding pattern.

3) Constructing the URL often has additional java logic in a CMS - perhaps you want to inject
some logic to translate external URLs that your translation provider doesn't translate (just
an example).  Ideally that code can stay in the model rather than requiring HTL to jump thru
another hoop.

4) For sling model exporters, there is no explicit "view" layer that the developer creates
"above" the model - it's a generic request handler.  If we don't do the externalization in
the model, where would we do it?

 

> Having a Resource + ResourceMetadata should be sufficient for roundtrip link mapping.
> -------------------------------------------------------------------------------------
>
>                 Key: SLING-8279
>                 URL: https://issues.apache.org/jira/browse/SLING-8279
>             Project: Sling
>          Issue Type: Wish
>          Components: ResourceResolver
>            Reporter: Mark Adamcin
>            Priority: Major
>
> With Sling Models, it is very easy to construct composite model types from more than
one resource, usually addressable as a subtree of the repository.
> However, a pattern is emerging where mapping is being performed to create related links
within the model, which mandates that SlingHttpServletRequest be used as the adaptable type,
because a Resource adaptable would not provide sufficient context for ResourceResolver.map().
Without a request for context, .map() would likely return incorrect links based on a default
base request URL of "http://localhost/".
> While on one hand, it might be argued that link mapping should only occur in the view,
after the model graph has been constructed, on the other hand, link resolution and resource
mapping are so fundamental to the correct behavior of a web application that we should take
advantage of every opportunity to make these activities more convenient and less error prone.
> If you trace the code for resource resolution and mapping, you will find that it relies
on just four discrete contextual properties that are currently available only from a request
object (i.e. not available from a Resource or its ResourceMetadata):
>  # scheme
>  # host
>  # port
>  # contextPath
> In addition, given that the ResourceResolver used by servlets when handling a request
is generally retrieved from the Sling Request itself using getResourceResolver(), it seems
redundant in concept, not to mention clumsy in practice, to require passing the request as
an argument back to the resource resolver (that was created specifically for the request in
question) in order to render links for any resources resolved while servicing that request.
> I think it is time to change the expected behavior of ResourceResolver.resolve(String),
ResourceResolver.map(String path), and other ResourceResolver methods that return resources
without an explicit HttpServletRequest parameter, such that:
>  # request.getResourceResolver().resolve(path) returns the same Resource as (any ResourceResolver).resolve(request,
path)
>  # request.getResourceResolver().map(path) returns the same String as (any ResourceResolver).map(request,
path)
>  # request.getResourceResolver().getResource(somePath).getResourceResolver().resolve(path)
returns the same Resource as request.getResourceResolver().resolve(path)
>  # request.getResourceResolver().findResources(someQuery).next().getResourceResolver().resolve(path)
returns the same Resource as request.getResourceResolver().resolve(path)
>  # etc.
>  # ResourceResolverFactory.getResourceResolver(Map) and ResourceResolverFactory.getServiceResourceResolver(Map)
would return ResourceResolvers that continue to use [http://localhost:80|http://localhost/]
as the default context url.
> If these constraints can not be satisfied reasonably using the existing resolve(String)
and map(String) methods, I would propose adding overloads that accept a context Resource in
place of the context HttpServletRequest, with additional properties added to ResourceMetadata
during request resource resolution that persist the four request context properties listed
above (scheme, host, port, contextPath).



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