A POV on Slice (a Adobe CQ Framework)
I have worked in Adobe CQ for last 18 months now; a large part of my not being active on this blog is because i was busy but the most important reason was that I wanted to understand the underlying technology before I go about writing it – best practices, what works and what does not and what not. Last I did about this was back in 2008 when I wrote about another Adobe product Flex 3.x.
Adobe CQ (Sling) background
If you don’t know what Adobe CQ is, you should go and read the documentation here and you will learn something new about a CMS system. I am looking at this framework today is Slice. I start by analysing the problems getting solved and I read the section they explain Why use it? I agree to all of these pain points in the Adobe CQ development system (actually let me clarify – i dont think any of this is Adobe CQ issue, this is a programming construct I see being used in underlying frameworks Sling). Refer to this document and you will notice that the problem arises where a lot of code sits naturally in a JSP (scripting language). This does not work well when you got to build enterprise applications and platforms on top of a product – the cost of managing the code is too high in the long run. The only way out is to fall back on enterprise standards (or best practices) of writing java and jee applications.
First of all, I have to appreciate that fact that people are thinking of solving for problems that we face during sling development. If you see the documentation, the model presented there is not ideal for a platform/enterprise version. I am not saying that is recommended from Adobe, and I am sure it has it’s place to be used. But, good to see others trying to solve for cases (Someday soon I will write more about the issues in current programming model).
What problems do we really need to solve for?
So my assuming you understand the construct and do understand the architectural principles of Sling (CQ) development, let me dive into my POV as if should I be using this framework or not. In CQ (Sling) I have been dealing with the following use cases. All the following use cases are about one thing i.e. reading data from the underlying data-store. Persisting the the data in CQ and how to render that (using JSP or other scripting language) is out of scope of this discussion primarily because this framework does not solves for those. Back to use cases, to list them (without a lot of detail)
- Read data stored on the same node where the component lives (stored via Dialog box)
- Read data stored in another node
- Aggregate data from several other nodes
- Search data using default (for now) APIs built into CQ (sling)
Does Slice addresses these issues
Use case 1: Read data stored on the same node where the component lives (stored via Dialog box)
If I read the basics of this framework here, use for the very first first use case does not make any sense; that is something we get from the framework OOTB. Sling framework puts all of the properties from the current node into a HashMap and exposes the same to us in JSP simply. I like to call this Content-in-Content-out approach of managing contents. So, why use a model in a JSP for something that already exists!! My bet is that this is not the case for which the framework was written and this was just the starting point like a building block to offer something more.
Use case 2: Read data stored in another node
Where things get interesting is the 2nd use case (read this advanced capability here). However, what this does is basically allows me to instead of making a call to an underlying JCR API to read the node, i can now refer to my Model to load the same stuff via a POJO. This makes things interesting, but do not interest me too much because of one primary reason this will make me model all of my content in to a model, but not string enough to reject this fully.
In all of my enterprise world we have been taught to work with DAOs and VOs basically define a model of our objects and then refer to them everywhere. This is a powerful construct that we all have been using it for ages and i wont even debate why we should not use it. But, in case of CQ, where the underlying framework converts the entire node into a HashMap. This programming model does not gives you a structure at times, but if the models are not complex and nested it is actually a pretty powerful way of dealing with data. CQ default is a Page based CMS and converting that to a content-based CMS kind of makes things tricky anyways.
Most of the components will invariably represent either a content-type or meta-data to fetch content can’t be modelled into POJO, there are so many of those (and lets not forget that we get all of that free or cost in properties). This will be POJO hell in no time. This leaves us with the use case of industry domains like in sports we might have an Athlete or a Venue that you can model into a POJO. You got to ask yourself the question, if you want to manage via POJOs or just use HashMap which makes the programming flexible. Work with properties – simple key value pairs or keep managing POJOs. I think at some point, I might use this framework for modelling the underlying content-structures into POJOs. However, i’d like to following certain principles in mind that i dont understand yet with Slice as to how they play out. Like we are injecting PageManagers which are core Day CQ APIs. What worries me is that if I have so much of underlying APIs strapped into my code, if anything was to change, I will end up re-writing so much of this. Maybe for a project a few months (maybe a quarter) I will give this a shot – saves me time to manage content. But, if i was writing a platform that would like several years and might actually see a major CQ upgrade, I really will think twice (maybe thrice) to use this framework.
Use case 3 and 4
The last two use cases are either built on top of this a Model and search is not catered by this use case. So basically if you’d ask me this framework provides a small coverage of a use cases and with the increased debt of managing another framework like Guice etc, if something was to change in CQ I might just be taking a lot of risk in refactoring later. Something that doesn’t makes me feel very comfortable.
Put simply in plain english
- For anything that is enterprise or platform(ish), I won’t go for this. The technical overhead that this framework and what it solves for is not worth the ROI of managing another framework
- If I’d come across strongly types content-types, I would consider to use this. The ultimate tie breaker would be how how many of the content-types need to be displayed “as-is”. If all i had to show are several compositions of data (search or what have you) maybe not. But, definitely something to consider
- I checked the roadmap, and I see very little activity – not something that will make me commit to using this long term
Not a lot of rope to hang off of; very little use cases to use and not exciting me much.