[Java] [Spring Client] Add an exception provider interface to allow for exception redefinition

[Mattias-Sehlstedt]

I have scenarios where I want to have more fine-grained control over the exceptions that an ApiClient can throw. This so that I can handle them more properly by distinguishing them by type and decorating messages. Doing this with the current structure is cumbersome since the same exceptions are redefined in several places, and they are strongly coupled to the enormous ApiClient.mustache. So I have to customize the base mustache to adjust this behavior.

In order to decouple the exception handling and provider better control over it, I suggest that it is extracted into an ExceptionProvider. This retains the current behavior of the exceptions thrown currently, but it also provides an extension point where these can be easily configured as a separate concept. Either with the ExceptionProvider.mustache, or by injecting an extended interface into the ApiClient.

This approach is currently tailored towards Spring's RestClient and WebClient only. RestTemplate is intentionally omitted, since it is deprecated.

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cc @bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04) @lwlee2608 (2019/10) @martin-mfg (2023/08)

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Summary by cubic

Adds an ExceptionProvider extension for Spring RestClient and WebClient Java clients to let users redefine thrown exceptions without touching ApiClient.mustache. Default behavior is unchanged and exception handling is now decoupled.

• New Features

  • Generate ExceptionProvider.java from ExceptionProvider.mustache for webclient and restclient.
  • Add exceptionProvider field with getter/setter in generated ApiClient; defaults to ExceptionProvider.DEFAULT.
  • Update JavaClientCodegen to include the supporting file for these libraries.

• Migration

  • No changes needed; defaults preserve current exceptions.
  • To customize: implement ExceptionProvider and call apiClient.setExceptionProvider(...).
  • Applies to Spring RestClient and WebClient only; RestTemplate is not included.

^{Written for commit 8f01653. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

7 issues found across 70 files

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