[BUG][Java][native] Wrong `Generated` annotation package for Java 9+

Created by: bbdouglas

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used? 4.1.0
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

Most clients use the following Generated annotation for the autogenerated code. This is correct for Java 8 and below, see Java 8 Generated javadocs.

@javax.annotation.Generated(value = "org.openapitools...", date = "...")

Starting with Java 9, however, it is now under a new package name (added the "processing" sub-package). See the Java 9 Generated javadocs for more info.

@javax.annotation.processing.Generated(value = "org.openapitools...", date = "...")

The current native HttpClient Generated annotation template still uses the old package name, and so if you set hideGenerationTimestamp=false, the code doesn't compile, since it runs in Java 11.

openapi-generator version

4.1.0

OpenAPI declaration file content or url

Any

Command line used for generation

Fails with all command lines that don't include hideGenerationTimestamp=true.

Steps to reproduce

See above

Related issues/PRs

N/A

Suggest a fix

I have a PR coming up to fix this for the native HTTP clientlib. It creates the correct annotation for Java 9+ inside a custom generatedAnnotation.mustache template inside the native resources directory.

Once more people start using Java 9+, a better alternative might be to have a Java 9 mode that would be incorporated into the shared generatedAnnotation.mustache file. But for now, I think this quick fix is easier.

The samples don't have to be re-created since they don't have the Generated annotation.