CQ coding patterns: Sling vs JCR (part 3)

In the last 2 postings (part 1, part 2) of the “Sling vs JCR” shootout I only handled read cases, but as Ryan D Lunka pointed out in the comments of on part 1, writing to the repository is the harder part. I agree on that. While on reading you often can streamline the process of reading nodes and properties and ignore some bits and pieces (e.g. mixins, nodeTypes), on the write part that’s a very important information. Because on the write part you define the layout and types, so you need to have full control of it. And the JCR API is very good in giving you control over this, so there’s not much room for simplification for a Sling solution.

Indeed, in the past there was no “Resource.save()” method or something like this. Essentially the resourceResolver (as a somehow equivalent of the JCR session) was only designed for retrieving and reading information, but not for writing. There are some front ends like the Sling POST servlet, which access directly the JCR repository to persist changes. But these are only workarounds for the fact, that there is no real write support on a Sling Resource level.

In the last months there was some activity in that area. So there is a wiki page for a design discussion about supporting CRUD operations within Sling, and code has been already submitted. According to Carsten Ziegler, the submitter of this Sling issue, this feature should be available for the upcoming version of CQ. So let’s see how this will really look like.

But till then you have 2 options, to get your data into the CRX repository:

  • Use the SlingPostServlet: Especially if you want to create or change data in the repository from remote, this servlet is your guy. It is flexible enough to cater most of normal use cases. For example most (if not all) of the CQ dialogs and actions use this SlingPostServlet to persist their data in the repository.
  • If that’s not sufficient for you, or you need to write structures directly from within code deployed within CQ, use JCR.

So here Sling currently does not bring any benefit, if your only job is to save data from within OSGI to CQ. If many cases the Default POST Servlet might be suffcient when you need to update data in CRX from external. And let’s see what CQ 5.6 brings with it.

3 thoughts on “CQ coding patterns: Sling vs JCR (part 3)

  1. Thanks for the follow up. I’m glad to see this is in the works. Carsten’s wiki page is very informational, and honestly, exactly along the lines of what I would expect in terms of API.

    1. Hi Daniel,

      thanks for your comment. Yes, this function is very limited, as it allows only to deal with properties. This limitation makes it unusable for most serious work, especially when I compare the functionality to JCR.


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