Refactoring of JSONCreate and XMLCreate to extract common logic

[redwanulsourav]

For #523
Key changes:
- Created CreateHandler.kt which extracts common logic between XMLCreate() and JSONCreate()
- Currently common logic handled: Check if database already exists and if not then create it
- Updated SirixVerticle.kt to use CreateHandler instead of XMLCreate and JSONCreate
- Created XMLCreate2.kt JSONCreate2.kt that has mostly code from XMLCreate.kt and JSONCreate.kt so that it is usable from CreateHandler.kt

TODO:
- Extract more common logic between XMLCreate2 and JSONCreate2
- Handle multipart/form-data with XMLCreate2 and JSONCreate2
- Handle and test resource creation using CreateHandler
- Eventually remove XMLCreate and JSONCreate

[JohannesLichtenberger]

I know I did something like that with few other handlers, but I think it would be worth considering if instead we could either encapsulate the common logic in abstract classes.

[JohannesLichtenberger]

Thanks for working on this @redwanulsourav 👍

[redwanulsourav]

I know I did something like that with few other handlers, but I think it would be worth considering if instead we could either encapsulate the common logic in abstract classes.

I agree, that would make it more modular. I was following the existing codebase and I thought that was how it was supposed to be done. I can implement this with abstracted classes and inheritance as well.

How it would be if I made CreateHandler a super abstract class, from which XMLCreate and JSONCreate would inherit? Later, all the common logic between handlers (CreateHandler, DeleteHandler) can be pushed upwords by creating an abstract class from which all the Handlers (CreateHandler, DeleteHandler) would inherit. If the Handlers don't have a lot in common, the super class can be turned into an interface as well. Does this plan sound ok?

[JohannesLichtenberger]

Yes, sounds like a good plan (though I think maybe it's useful to have different abstract classes from which the XML and JSON implementations inherit for the CRUD stuff). XmlCreateHandler extends AbstractCreateHandler, JsonCreateHandler extends AbstractCreateHandler... and analogous the other types. I think it's better to stop at this point instead of to refactor to one big abstract class, but we'll see :-)

[redwanulsourav]

I will do that and create a new PR. For now I am closing current PR. Thanks for the instructions.

[JohannesLichtenberger]

Thanks for your work and interest in the project!