Change default for `SerializationFeature.FAIL_ON_EMPTY_BEANS` to `false`

[gregorriegler]

I would expect an empty Object without any field to be rendered as {}

When I drove a Spring Boot Rest API with an Acceptance Test step by step, I tried to respond with an empty Object at one point, expecting an empty Json Object as a response.
However, Spring noticed that Jackson would not serialize this Object, and instead jumped to the next Converter which caused unrelated Issues. It took me about 1 hour of analyzing at the wrong end, to figure out the real cause.

I think it would be beneficial for developers, if the default of FAIL_ON_EMPTY_BEANS was false, and an empty Json Object would be created in that case.

[cowtowncoder]

Default settings changes are possible for the major version upgrade, although we'd need to figure out some way to gauge how popular change proposals are.
Marking as 3.0.

[jrieko]

Presupposing the intention of this feature is to warn the user about potential mistakes in serialization configuration, I'd assert some arguments against a survey/proposal precluding this change:

• This behavior is incongruous with other JSON serializers.
  • The JSON representation of an object with no properties is {}. I don't see any ambiguity there which warrants blocking the user until they confirm this is what they expect.
  • I would expect the default behavior of a serializer to produce the standard unambiguous JSON representation.
• Use exceptions only for exceptional conditions (Effective Java (3rd), Item 69). I don't think a potential configuration mistake is an exceptional condition.

[cowtowncoder]

I will proceed with this change, so default will change for Jackson 3.

[cowtowncoder]

Changed for 3.0.0-SNAPSHOT (master branch).