feat(builder): Builder pattern support for entities creation

[abourdon]

Hi,

Please accept this PR that adds the ability to use the Builder pattern during FROST-Client's Entity creation:

final Thing thing = ThingBuilder.builder()
  .name("Camera")
  .description("This thing is a camera.")
  .build()

In addition, any FROST-Client's entity builder can be extended. This way, FROST-Client clients could define their own way to construct OGC SensorThings' entities (by creating new FROST-Client's entity builders) and so could help to partially extend the FROST-Client's entity model (#3):

public final class MyCustomObservationBuilder extends AbstractObservationBuilder<MyCustomObservationBuilder> {

    private MyCustomObservationBuilder() {
    }

    public static MyCustomObservationBuilder builder() {
        return new MyCustomObservationBuilder();
    }

    @Override
    protected MyCustomObservationBuilder getSelf() {
        return this;
    }

    /**
     * Can only handle {@link MyCustomResult} type as Observation#result
     */
    public MyCustomObservationBuilder result(final MyCustomResult result) {
        return super.result(result);
    }

}

Finally, this PR includes:

• A new way to construct FROST-Client's entities, by using the Builder pattern
• The ability of any FROST-Client's entity builder to be extended to try to be more compatible with FROST-Client client needs
• A fluent API when using FROST-Client's entity builders
• A fully compliance with the OGC SensorThings' entities specification when using FROST-Client's entity builders interfaces

Regards,
Aurélien

[hylkevds]

Wow, that looks nice!

Maybe we can somehow get the json parser to also use this...

[hylkevds]

Is that supposed to be here? It'll return a new MultiDatastream each time...

[abourdon]

Oups, well seen ;-) I fix it.

[abourdon]

@hylkevds thanks ;-)

IMHO it is not necessary to use it within the JSON parser as you are using the Jackson library that provides lot of nice features based on your entity model. Those builders are more oriented to FROST-Client's users that want to manually create entities.

[abourdon]

@hylkevds, thanks. Could it be possible to release a 0.16 version that incorporates these changes?

[hylkevds]

Done :)
Forgot to update the change log again...

[abourdon]

Thanks! Yes and the README.md should also be updated to point to this new version: https://github.com/FraunhoferIOSB/FROST-Client#using-with-maven

[hylkevds]

Good point... haven't heard back from JFrog/Bintray yet. I'll change the maven howto till they fix the issue.