Allow late-binding or reconfiguration of `TokenStreamFactory` on `MapperBuilder`

[mhewedy]

Is your feature request related to a problem? Please describe.

Currently, JsonMapper.Builder requires the JsonFactory at construction time. In managed environments like Spring Boot, the builder is often instantiated by the framework before the user can provide a custom factory (e.g., for CharacterEscapes). This makes it impossible to customize the factory without discarding the entire builder state. Adding a .streamFactory(factory) setter to the builder would resolve this.

Describe the solution you'd like

Adding a .streamFactory(factory) setter to the builder

Usage example

No response

Additional context

No response

[pjfanning]

There is a spring-boot solution because I was CCed by GitHub about some comments added to a spring-boot issue a few days ago. Maybe you could search the spring-boot issues and PRs for comments about creating custom JsonFactories.

[pjfanning]

See spring-projects/spring-boot#34709 (comment)

If jackson-databind adds a change, you will be waiting for a Jackson release and then a Spring-Boot release that uptakes that Jackson release.

So in medium term you are stuck with what's there.

[pjfanning]

This relates to spring-projects/spring-boot#48594

Rewriting the MapperBuilder and its subclasses to allow the JsonFactory to be provided later will take a fair amount of work. The code as is, is pretty heavily tied to having the factory at MapperBuilder construction time.

[cowtowncoder]

I don't think we will try to implement such a change. I have gut feeling this would indeed be a big and challenging undertaking as @pjfanning is suggesting.
Mostly because mappers and their builders are format-specific; there is no generic, format-agnostic MapperBuilder to use, just sub-classes.
And builders cannot dynamically change their own type.

But leaving open for time being, just in case someone and has good ideas & proposes a way forward.