Modelling restful properties


I’ve recently been playing with Liberty and JAX-RS and in an effort to remember some of what I’ve discovered, I’m going to try and keep a few notes and post them here, probably along with a few questions. If anyone else finds them useful, or knows the answers, that’s a bonus!!

To start with Creating an efficient REST API with HTTP provides a nice overview of REST APIs and JAX-RS basics has a great simple sample application to get going with… and break!

JAXRSServiceModel_Main

Armed with the basics I thought it would be interesting to model the sample application to compare the working code with what Rational Software Architect (RSA) would generate for me. Obviously that’s not the most complex model in the world but it was good to have a few examples to follow:

(Those articles made much more sense when I’d tracked down all the likely looking JAXRS, REST and UML features in the RSA installer!)

Before generating any code, it was quite nice to get some basic API documentation out of the model. Not as fancy as using Swagger UI but certainly better than no documentation!

systemproperties-apidoc

It’s only a start but that’s all for part 1. Hopefully there’ll be more posts at some point when I get further, probably along these lines:

  • Creating an OSGi Web project and generating some code
  • Using a REST client to check it works, including a puzzling Wink problem
  • Adding some debug
  • Expanding the sample with some awkward long running processing
  • Deploying to Bluemix
  • Anything else I encounter along the way!

If you know of any good articles/books/fancy new media that would help, please leave recommendations below. If there are better ways to design REST services (Swagger looks interesting but I haven’t had a chance to investigate), please share them. And any other tips, comments, or questions of your own are also very welcome!

 

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Conference User Model


I hope to get round to blogging about the actual Code Generation conference at some point but this is about another Code Generation conference app. I’ve been playing with a user model based on an example at the conference and, since I mentioned the user interface generator to a few people, I thought it might be useful to share a few diagrams from the model here. If you were at the conference, and/or have looked at the Code Generation 2011 Android app, you’ll probably recognise these basic entities:

(At this point I had to stop myself going a bit mad with user objects for venues, rooms, capacities, etc. etc. etc.!)

Instead of focusing on the look and feel of a user interface, user modelling allows you to create a specification of a system from the user’s point of view. So, for example, a conference delegate might have a goal of attending a conference, which would consist of a number of tasks, like registering for the conference. The diagram below shows part of the model, with a simple task to view the available sessions:

By default, the <<select>> and <<view>> keywords on the associations between the View sessions task and Session object will generate the following activity diagram:

The user interface generator handles on screen presentation of the user objects for each of the <<ui_change>> actions in the activity diagram, while the <<command>> actions represent code that must be written to fetch data from some system. This could be code to call MDM Server transactions and, since the user interface generator is provided with MDM Server, this code can also be generated to create a basic sample data maintenance user interface. There’s no technical reason to prevent the commands getting data using any web services, or direct from a database, or anywhere really. To test drive a UI, there’s an option to generate all the code necessary for a simple file based data store for example.

Having generated enough of the user interface to view sessions, I wanted to add a way to favourite sessions like the Android app. The next diagram shows a customised activity diagram to do this:

You can see that after the UI change to view a selected session, there is now a decision with two options; there’s a Favourite flow in addition to the previous Done flow, which appears as another button in the UI. I could change the model again to make it possible to mark multiple sessions as favourites at the same time, which would require changing the cardinality of the task to user object relationship, as well as another decision node in the activity diagram. The last diagram from the model shows a more complex activity diagram that has a similar extra decision node, but for a task to manage conference tracks:

If you’re interested in finding out more about user modelling and the user interface generator, there’s an article on developerWorks. and some related blog posts. I’ve also blogged here about user modelling in the past.

Any questions or comments would be very welcome indeed.