[Java][Spring] Place @Valid on Optional/JsonNullable type argument (HV000271)

[jorgerod]

Fixes #25097. Follow-up to #24176.

#24176 moved @Valid from List/Set/Map containers to their type argument. The Java Spring generator still emits a member- or parameter-level @Valid when a single model is wrapped in Optional (useOptional) or JsonNullable (openApiNullable). Hibernate Validator 9.1+ treats both wrappers as containers (JsonNullable through the ValueExtractor registered by jackson-databind-nullable), so this still logs HV000271.

Changes

Case	Before	After
Model field/getter, useOptional	@Valid Optional<Item> getSingleItem()	Optional<@Valid Item> getSingleItem()
Nullable model field/getter, openApiNullable	@Valid JsonNullable<Item> getX()	JsonNullable<@Valid Item> getX()
Optional query (deepObject) / multipart / body model param	@Valid ... Optional<Item> item	... Optional<@Valid Item> item
Optional scalar body	@Valid @RequestBody(required = false) Optional<String> body	@RequestBody(required = false) Optional<String> body

• Only models get the type-argument @Valid. Wrapped scalars (Optional<BigDecimal>, JsonNullable<String>…) have nothing to cascade into, so they get none. This matches what fix(java): place bean-validation @Valid on the type argument instead of the container (HV000271) #24176 did for scalar query/form params.
• Required or unwrapped single objects keep their member/parameter-level @Valid.
• A new typeUseAnnotations Mustache lambda (AbstractJavaCodegen#placeTypeUseAnnotations) places type-use annotations after the package qualifier of fully qualified types, e.g. JsonNullable<com.example.@Valid ExternalModel>. The form <@Valid com.example.ExternalModel> does not compile (seen with schemaMapping and with Resource/Instant types).

Tests

• SpringCodegenTest: new tests on 3_0/spring/issue_25097_valid_container.yaml covering the model getters/fields (Optional, JsonNullable, Lombok), optional query/form/body params, FQN types, and regression guards for the cases fixed in fix(java): place bean-validation @Valid on the type argument instead of the container (HV000271) #24176 (list/map params, DTO getters, composed array items, nested maps). Three existing expectations were updated to the new output (Optional<@Valid Zebra>, JsonNullable<com.example.@Valid ExternalModel>).
• JavaClientCodegenTest: regression guard for container DTO getters (resttemplate/native/webclient).
• AbstractJavaCodegenTest: unit test for placeTypeUseAnnotations.
• ParameterAssert#hasAnnotatedType: new assertion that keeps type-use annotations. The existing hasType ignores them.
• org.openapitools.codegen.java.** passes: 1267 tests, 0 failures.
• Runtime check: I validated the generated Spring models and API interfaces (ExecutableValidator) with Hibernate Validator 9.1.3.Final, using invalid nested payloads. HV000271 is gone, and nested violations are still reported with no duplicates.

PR checklist

• Read the contribution guidelines.
• Ran the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  Regenerated bin/configs/spring*.yaml and bin/configs/java-camel*.yaml, the only generators using the changed JavaSpring templates. All changed sample projects compile.
• Mentioned the Java Spring technical committee: @cachescrubber @welshm @MelleD @atextor @manedev79 @javisst @borsch @banlevente @Zomzog @martin-mfg @KannaKim

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Summary by cubic

Fixes HV000271 by placing @Valid on the type argument of Optional/JsonNullable-wrapped models instead of the member or parameter, so generated code now emits Optional<@Valid Item>.

• Wrapped models on fields, getters, query/form/body params, and Lombok accessors now carry @Valid on the type argument; wrapped scalars get none, and required or unwrapped models keep their member/parameter-level @Valid.
• Adds a Mustache lambda that places type-use annotations after the package qualifier of fully qualified types (e.g. JsonNullable<com.example.@Valid ExternalModel>), the only form that compiles.
• Updates existing expectations and regenerated samples for the new output; all changed sample projects compile.
• Covers regression guards for container cases from fix(java): place bean-validation @Valid on the type argument instead of the container (HV000271) #24176 (list/map params, DTO getters, composed array items, nested maps).

^{Written for commit 07b96a7. Summary will update on new commits.}