Dynamically change/delete registered modules

[shvydkov]

Is it possible to somehow operate object mapper's registered modules on a flight? I'm trying to dynamically add serialisers&deserialisers for a LocalDate, so multiple date formats can be supplied/sent via a service based on the locale.

I intercept a http call and register a module with required date format serialiser&deserialiser but this leads to duplication and polluting Jackson registered modules, as it's being saved exactly how many requests I make.

Not sure if there's a mechanism to optimally delete a module, or overwrite it?

[cowtowncoder]

Short answer: No. And not really possible to do with the architecture.

Longer answer differs a bit between current Jackson 2.x (no -- there's no way to remove modules) and 3.x (can remove during building; or rebuild()).

But basically Modules make kinds of changes that cannot be dynamically modified once ObjectMapper is in use.

So if you want to have different modules (or differently configured), you need separate mappers.

[pjfanning]

I don't see why statically configuring a mapper with all the modules you might need is a bad thing. It may slow down runtime introspection a bit if you have lots of modules registered but the results of the introspection are cached on the mapper instance. So the slowdown only affects the first time you bind to a specific class.

[cowtowncoder]

I think @shvydkov said they need different (de)serializers based on config, so fully static setup wouldn't work.

[cowtowncoder]

Also worth noting: you really cannot reliably add any new Modules after using an ObjectMapper. It may happen to work for some cases but due to concurrency, may very well fail in spectacular ways.
Jackson 3.0 will prevent any such attempts (since Modules are added via Builder, not mapper directly), but with 2.x you need to be aware of "Config-then-Use" pattern for ObjectMapper
(configuration via ObjectReader / ObjectWriter is fine, just not ObjectMapper).