[dmunozfer]

Fixes #25463

Problem

The source contract has an optional array query parameter with no default. The openapi-yaml bundling pass emits default: null; generating from that bundled contract can produce defaultValue = "null", changing the behavior of an omitted query parameter.

Root cause

The bundled document represents the null default as a Jackson NullNode. AbstractJavaCodegen.toDefaultParameterValue treated that node as a value and stringified it. Spring and Micronaut Java generators use this shared conversion path.

Solution

Null Jackson nodes are now treated as no parameter default in AbstractJavaCodegen. A schema-local default takes precedence over the referenced schema default, preserving explicit $ref sibling defaults such as the literal string "null".

Regression coverage

The OpenAPI 3.1 fixture and Spring spring-http-interface test cover null and absent defaults, explicit scalar and array defaults, literal string "null", and referenced schemas with and without a sibling override. The shared Java base conversion addresses the same behavior in Micronaut server and client.

Compatibility

The behavior change applies to generators extending AbstractJavaCodegen; non-Java generators and templates are unaffected.

[cubic-dev-ai]

All reported issues were addressed across 3 files

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[cubic-dev-ai]

All reported issues were addressed across 3 files (changes from recent commits).

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[wing328]

thanks for the PR

cc @cachescrubber (2022/02) @welshm (2022/02) @MelleD (2022/02) @atextor (2022/02) @manedev79 (2022/02) @javisst (2022/02) @borsch (2022/02) @banlevente (2022/02) @Zomzog (2022/09) @martin-mfg (2023/08) @KannaKim (2026/07)

[Sekator778]

Reproduced #25463 on master, and this fixes Spring. The same bundled spec still gives @QueryValue(value="ids", defaultValue="null") in java-micronaut-server and java-micronaut-client. The same null check in AbstractJavaCodegen.toDefaultParameterValue fixed both in my run; would you move it there?

[dmunozfer]

Thanks for reproducing this in both Micronaut generators. You were right: AbstractJavaCodegen.toDefaultParameterValue is the shared conversion path. I moved the Jackson-null handling there, kept schema-local $ref sibling defaults ahead of the referenced default, and removed the Spring-only override. The change is in commit 19ac4e2; the existing Spring regression coverage remains in place, and CI will rerun on the updated head.