Completing object construction after GSON deserialization

I would likely take the second approach, because as I typically design my applications, anything that needs to be serialized/deserialized is really just plain old data, or POJOs if you prefer. If I find myself needing to customize/configure the serialization API to do what I want, I tend to simplify what's being serialized, so the serialization API doesn't need the extra configurations.

So, if I have a more complicated data model, parts of which aren't to be serialized/deserialized, then I extract from it a simpler set of POJOs, as a conceptually separate data model to participate in the serialization/deserialization. This does then indeed require an extra step to map between the two data models, but that's usually pretty simple, also.

If the third approach is preferred, then note also the Instance Creator feature, as it can provide another useful hook into customizing the deserialization process.

Check out https://github.com/julman99/gson-fire

It's a library I made that extends Gson to handle cases like Post-serialization and Post-deserialization

Also it has many other cool features that I've needed over time with Gson.