com.gluonhq.attach.util.Services refactored

[DanskerDave]

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[DanskerDave]

As discussed in Mail with José Pereda

[DanskerDave]

Hi José,

I've created a Fork & made 2 commits to it.
How do I make that available to you?
(as you see, I'm just as new to git as I am to Gradle) :-)

Here's what I did (& didn't) change...

Firstly, an observation:
many of the classes I looked at do not seem to take account of Multi-Threading, synchronized etc...

I have not addressed that at all.

Here are the details of my changes:

com.gluonhq.attach.util.impl.DefaultServiceFactory

Class.forName never returns null (at least, according to Javadoc)

-> superfluous null-check removed

com.gluonhq.attach.util.Services

The Javadoc of the registerServiceFactory(...) Method was incorrect.

-> Javadoc corrected

-> I added Objects.requireNonNull(factory.getServiceType()) to the Method

The current get(...) Method always does a Lookup in FACTORY_MAP,
even when the Service has already been resolved.

-> I have removed the superfluous Lookup.

Every time a Service is requested, its wrapped in a new Optional.

-> Instead of wrapping the Service instance anew every time,
I wrap it once and store the resulting Optional in the Map,
thus speeding up subsequent calls.

-> also, I've commented the Method extensively

-> the behaviour of the rewritten Method is identical to the old version.

The new Java11+ Version has unreachable code:
now that DefaultServiceFactory is no longer abstract,
ServiceFactory can never be null & the RuntimeException will never be thrown.
(instead, DefaultServiceFactory.createInstance(...) will generate a LOGGER.warning)

-> unreachable new RuntimeException(...) removed

I've also included a Dummy SERVICE_NULL_ENTRY to speed things up even more.
You need to read the Comments in the Source to decide if that's desired.

All the best,
Dave