[BUG] [Java] Invalid code generation for oneof types.

[Bethibande]

Fixes #18517, Gradle builds work again using the test file: https://gist.github.com/Bethibande/c97b0b64e3dc284c056c02fbf3778a9b

PR checklist

• [x] Read the contribution guidelines.
• [x] Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• [x] Run the following to build the project and update samples:

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

  (For Windows users, please run the script in Git BASH) Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• [x] File the PR against the correct branch: master (upcoming 7.1.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)

[wing328]

thanks for the PR.

can you please add a test model (oneOf with map as sub schema) in modules/openapi-generator/src/test/resources/3_0/java/petstore-with-fake-endpoints-models-for-testing-okhttp-gson.yaml?

[Bethibande]

Going to add the unit-tests later. EDIT: Never mind, just found out the sample Test classes are all empty.

[wing328]

when you've time, can you please add a unit test or 2 in https://github.com/OpenAPITools/openapi-generator/blob/c80075bc2ee24634a5124a52d3088d11b6b13719/samples/client/petstore/java/okhttp-gson/src/test/java/org/openapitools/client/JSONTest.java ? (which contains many examples on unit testing the models)

[wing328]

https://github.com/OpenAPITools/openapi-generator/actions/runs/8920607680/job/24599035459?pr=18544

please update the samples and add new files

[wing328]

thanks for the PR, which has been merged.

https://github.com/OpenAPITools/openapi-generator/actions/runs/9016604828/job/24773787312 fixed via eec30f2cdac