[SLING-8279] Having a Resource + ResourceMetadata should be sufficient for roundtrip link mapping.

• Type: Wish
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: ResourceResolver
• Assignee: Unassigned
• Reporter: Mark Adamcin
• Created: 18/Feb/19 22:42
• Updated: 29/May/19 17:34

Description

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):

1. scheme
2. host
3. port
4. 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:

1. request.getResourceResolver().resolve(path) returns the same Resource as (any ResourceResolver).resolve(request, path)
2. request.getResourceResolver().map(path) returns the same String as (any ResourceResolver).map(request, path)
3. request.getResourceResolver().getResource(somePath).getResourceResolver().resolve(path) returns the same Resource as request.getResourceResolver().resolve(path)
4. request.getResourceResolver().findResources(someQuery).next().getResourceResolver().resolve(path) returns the same Resource as request.getResourceResolver().resolve(path)
5. etc.
6. ResourceResolverFactory.getResourceResolver(Map) and ResourceResolverFactory.getServiceResourceResolver(Map) would return ResourceResolvers that continue to use http://localhost:80 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).

Issue Links

• relates to: SLING-5726 Allow ValueMapInjector and ResourcePathInjector to act directly on SlingHttpServletRequest