[JAVA] JAXB models should not have to include JSON-related annotations

Description

I am testing the recently improved support for generating JAXB-based models (#5962 and #6005).
The generated code always includes JSON-related annotations, which are unnecessary for a XML-based API.

Swagger-codegen version

2.2.3-SNAPSHOT

Configuration file

{
  "sourceFolder" : "src/main/java",
  "withXml": true,
  "modelPackage" : "my.model.package",
  "additionalProperties" : { 
    "gson": false 
  }
}

Command line used for generation

    java -Dmodels -jar swagger-codegen-cli.jar \
        generate -i swagger.json  -l java -c config.json

Steps to reproduce

Run the generator using the provided configuration file and any Swagger spec. Observe the generated model classes end up with references to annotations and types from com.google.gson. It is fine if that is the default, but it should not be mandatory.

Related issues

Suggest a Fix

I can change my configuration using the library option to choose a different JSON library. Maybe I should be able to specify "none"?

Start by running the Java generator with the provided config.json and swagger.json, then inspect the generated model classes for com.google.gson references. Trace the Java model generation entry point and templates involved in JAXB output; done means XML-only generation no longer requires JSON annotations or Gson types when gson is false.