[BUG][java] CustomTypeAdapterFactory incorrectly assumes non-primitives are json objects

[ashatch]

Bug Report Checklist

• [ ] Have you provided a full/minimal spec to reproduce the issue?
• [ ] Have you validated the input using an OpenAPI validator (example)?
• [x] Have you tested with the latest master to confirm the issue still exists?
• [x] Have you searched for related issues/PRs?
• [ ] What's the actual output vs expected output?
• [ ] [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

pojo.moustache's CustomTypeAdapterFactory.create populates properties by testing for e.g. primitive types for values. It's else block makes an assumption that if it isn't a primitive type, it must be an object:

gson.toJsonTree(entry.getValue()).getAsJsonObject()

This fails when considering arrays.

openapi-generator version

master

Suggest a fix

I'll raise a PR.

[wing328]

can you please share a spec to reproduce the issue?

[wing328]

closed via https://github.com/OpenAPITools/openapi-generator/pull/17812