[BUG][Java][Spring] useBeanValidation=false still generates jakarta.validation.constraints.NotNull

[BUG][Java][Spring] useBeanValidation=false still generates jakarta.validation.constraints.NotNull

Description

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue? (See repro steps)
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
  • Actual: Compilation failure due to missing jakarta.validation packages.
  • Expected: Code should compile without requiring Jakarta Validation dependencies when useBeanValidation=false.

Description

When useBeanValidation is set to false, the generator continues to produce jakarta.validation.constraints.NotNull annotations and imports for required properties. This creates a technical contradiction: the generator assumes the existence of a validation library that the user has explicitly opted out of.

The "Masking" Problem:
This compilation error is frequently masked because the default documentationProvider=spring pulls in the Jakarta Validation API transitively. However, when a user sets documentationProvider=none and useBeanValidation=false, the project lacks the necessary classpath dependency, leading to a build failure.

Better Alternatives:
Since the original implementation of this feautre, we have better ways to handle nullability hints without forcing a runtime validation dependency:

• useJSpecify=true: Provides annotations for IDE-level and compile-time linting.
• org.springframework.lang.Nullable: same as JSpecify, and generated by default .

openapi-generator version

Detected in 7.x. Based on git history, this appears to be a regression/side-effect of changes made around version 6.2.1 and 6.8.

OpenAPI declaration file content or url

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/test/resources/3_1/petstore.yaml

Generation Details

{
  "generatorName": "spring",
  "inputSpec": "petstore.yaml",
  "outputDir": "out",
  "additionalProperties": {
    "library": "spring-cloud",
    "useBeanValidation": false,
    "documentationProvider": "none"
  }
}

Steps to reproduce

# clone the openapi-generator repo
git clone https://github.com/OpenAPITools/openapi-generator.git

# into the dir of the petstore yaml
cd openapi-generator/modules/openapi-generator/src/test/resources/3_1

# generate code with validation disabled and no documentation provider
docker run --rm -v ${PWD}:/ws -w /ws openapitools/openapi-generator-cli generate -g spring -i petstore.yaml -o out -p 'library=spring-cloud,useBeanValidation=false,documentationProvider=none'

# attempt to compile
docker run --rm -v ${PWD}/out:/ws -w /ws maven mvn package

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.13.0:compile (default-compile) on project openapi-spring: Compilation failure:
[ERROR] /ws/src/main/java/org/openapitools/model/Pet.java:[16,38] package jakarta.validation.constraints does not exist
[ERROR] /ws/src/main/java/org/openapitools/model/Pet.java:[142,4] cannot find symbol
[ERROR]   symbol:   class NotNull
[ERROR]   location: class org.openapitools.model.Pet

Related issues/PRs

• PR #13580: Introduced @NotNull for required fields even when useBeanValidation=false to reflect schema requirements.

• PR #13941: Added the missing jakarta.validation import to fix compilation errors reported in #13885.

• The Conflict: While #13941 fixed the immediate missing import error, it solidified a mandatory dependency on Jakarta Validation that ignores the useBeanValidation=false flag.

• issue https://github.com/OpenAPITools/openapi-generator/issues/16441 similar observation

Suggest a fix

• Respect the Flag: If useBeanValidation=false, the generator should not produce any jakarta.validation imports or annotations. Proposed Fix
• Runtime Safety: If guarding against null is required at the generated code level, consider using Objects.requireNonNull in the constructor and setter instead of a validation annotation. Proposed Fix
• Linting: Users who want compile-time hints without validation overhead should be encouraged to use the useJSpecify=true flag.
• Proposed Feature (Breaking Change): To provide a clear path forward and avoid surprises, consider evolving useBeanValidation into a multi-value option:
  • NONE: No jakarta.validation annotations (The proposed fix for the current false setting).
  • REQUIRED_ONLY: Generates @NotNull for required fields only (The current behavior for false).
  • ALL: Full bean validation (The current behavior for true).
  • implementation spec/plan

Reproduce the issue from modules/openapi-generator/src/test/resources/3_1/petstore.yaml using the shown Spring configuration, then run Maven package on the generated output. Review PRs #13580 and #13941 alongside the proposed fixes to determine the intended behavior; done means validation is not required when useBeanValidation=false and the generated project compiles without jakarta.validation.