Implement Jackson3 support and maintain Jackson2 support

[smals-mavh]

Summary by cubic

Add Jackson 3 support alongside Jackson 2 so JsonNullable works on both runtimes. This introduces a Jackson3 module with serializers/deserializers and refactors the Jackson2 implementation to keep compatibility.

• New Features

  • Jackson 3: JsonNullableJackson3Module with serializers, deserializers, type/value serializer modifiers, and unwrapping writer.
  • Auto-discovery for Jackson 3 via META-INF/services/tools.jackson.databind.JacksonModule.
  • Test coverage for both versions using Jackson2Processor and Jackson3Processor with parameterized tests.

• Refactors

  • Renamed Jackson 2 classes to JsonNullableJackson2* and wired JsonNullableModule to these implementations.
  • Split BOMs in pom.xml (jackson2-bom and jackson3-bom) and updated module-info and service-loading tests.

^{Written for commit cb6dfbf. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 36 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="pom.xml">

<violation number="1" location="pom.xml:40">
P2: Jackson 3 requires Java 17+, but the build is pinned to Java 8. Adding the Jackson 3 BOM/tools.jackson dependencies will make builds fail with class file version incompatibility unless the toolchain is upgraded or Jackson 3 is isolated.</violation>
</file>

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[smals-mavh]

Some extra context:

• Kept the name 'JsonNullableModule' instead of JsonNullableJackson2Module for example to keep some backwards compatibility
• The jackson library is marked as 'provided' in the pom now (to not have any jackson version conflicts downstream). The disadvantage is that users now need to add jackson to their pom.
  • On that note, we could add jackson-annotations since they're the same for both Jackson2 and Jackson3 for the moment. But might not be super future proof.
• Parameterized tests are a bit shoe-horned in some places, but to me this seemed to be the 'safest' route to make sure that all tests work with both Jackson versions.
• Tested in both Spring Boot 3 and Spring Boot 4 projects and had no issues (apart from having to add the jackson libs myself since they're not transitive anymore)

[SirBigoo]

I'm waiting this PR to be released because I can't migrate to spring 4 without breaking my app behavior... 💯

[antechrestos]

@wing328 is there any chance that this PR gets merged? This could be useful to add it once useJackson3 get supported by open api generator