Support FilterProvider with EMFJson

[martin-fleck-at]

Jackson supports filter provider (@JsonFilter) that filter out certain objects during serialization. It seems that there is currently no way to apply the same mechanism to EMF JSON-Jackson.

This issue was raised in eclipse-emfcloud/emfcloud#118

[vhemery]

Using @JsonFilter would mean adding the annotation on the generated class for the EClass...
I don't really see how to achieve it easily for the user. The options to add this annotation (on the interface or on the Impl ?) are:

• rewriting the generated code
• using custom templates
• using EMF with non-generated java classes

Also note that we already support a JsonIgnore EAnnotation on the Ecore model, which looks much more convenient.

So I fail to grasp what the support for filter providers would bring...
Do we have a concrete use case example with EMF classes?

[martin-fleck-at]

Hi @vhemery,

Thank you, I really appreciate your input! It's been a while since this feature request was opened and so far I've not seen anyone report a need for this. The original request also did not specify a concrete example, so there is not much I can add to this discussion. Are you facing a need for it? If not, we could consider closing this issue at some point.

[vhemery]

No need for me. Like I said JsonIgnore EAnnotation makes the job better.
I was considering implementing it for the sake of contribution, but was having a hard time to write a valid unit test (where to put the @JsonFilter annotation).

[martin-fleck-at]

@vhemery I see, that is very kind and I really appreciate it. If you already have something ready, I'd suggest to just come up with an artificial example, otherwise we may skip this for now.