Discovery by parsing : Hook in FraSCAti to detect a composite start in a standalone FraSCAti

[JGuillemotte]

See Discovery by SCA parsing issue : https://github.com/easysoa/EasySOA/issues/28

FraSCAti Hook Issue :

Currently, the SCA import works only with a composite file specified in the SCA import Nuxeo page. We want to integrate more the smarttravel trip sample in the demo, especially to discover services when a sample is started in FraSCAti.

In the current demo release (0.3), the smarttravel trip sample is started in an external FraSCAti engine. As the SCA import works in an Nuxeo embeded FraSCAti engine, it is not possible to make a deeper integration.

Here we have 2 Solutions :

Use an Nuxeo embeded FraSCAti and start the sample in this engine : this solution can be used in a development platform or for a short term solution. or still use an external FraSCAti engine and add a hook to plug custom features on the composite processing cycle. Good solution in situations where a Frascati engine is not on the same platform that Nuxeo.

The solution could be to add a hook in FraSCAti : This hook could work with a 'LifeCycleListener' interface which defines a 'handle' method with 2 parameters : the processing mode and the processing context. To indicate if FraSCAti have to send events to a lifecycle listener, we can use a parameter in the FraSCAti launch command.

For the next release of the demo, if we have FraSCAti works in Nuxeo, we could start the smarttravel sample in the Frascati Nuxeo embeded.

[JGuillemotte]

Solution proposed by C. Munilla :

Put a discovery hook solution based on a intent.

How it work :

• A shared library allow to share the ParserIntentObserver and ParserIntentObservable definition between EasySOA and FraSCAti (to put in Registry/lib)
• An SCA intent (which is also a ParserIntentObservable) is woven to the composite-parser of the FraSCAti instance (nuxeo-frascati module)
• A new ParserIntentObserver can be registered using the FraSCAtiServiceItf (NuxeoFraSCAti)
• The newComposite method of the ParserIntentObserver will be call each time the FraSCAti instance will load (parse) a new composite

The Parse-intent is linked programmatically to the SCA Parser in the FraSCAtiServiceItf class.

Limitations :

• does not send notifcations to EasySOA => either add it to the intent BUT not an atomic operation for all of an app's composites (see next point), or add code (ex. as another woven Intent) that does it after the processComposite() (ex. in FraSCAtiApp.start()) but then has to empty the observer after each notification
• records parsed instead of fully instantiated composites => move current Intent or weave in another one there

See https://github.com/easysoa/EasySOA/blob/master/easysoa-registry/nuxeo-frascati/src/main/java/org/nuxeo/frascati/NuxeoFraSCAti.java

Both limitations can be solved by weaving in other intents. We will choose the way and do it once all functional requirements & business uses are known, see #79 (& #21) .