[java/scala] ClassCastException: RefParameter cannot be cast to BodyParameter

Description

Caused by: java.lang.ClassCastException: io.swagger.models.parameters.RefParameter cannot be cast to io.swagger.models.parameters.BodyParameter
        at io.swagger.codegen.DefaultCodegen.fromParameter(DefaultCodegen.java:2574)
        at io.swagger.codegen.DefaultCodegen.fromOperation(DefaultCodegen.java:2213)
        at io.swagger.codegen.languages.AbstractJavaCodegen.fromOperation(AbstractJavaCodegen.java:1057)
        at io.swagger.codegen.DefaultGenerator.processOperation(DefaultGenerator.java:881)
        at io.swagger.codegen.DefaultGenerator.processPaths(DefaultGenerator.java:811)
        at io.swagger.codegen.DefaultGenerator.generateApis(DefaultGenerator.java:431)
        at io.swagger.codegen.DefaultGenerator.generate(DefaultGenerator.java:746)

Swagger-codegen version

2.3.1-SNAPSHOT

Swagger declaration file content or url

Like open API 2.0 demo, my open API defination below:

...
"parameters": [
          {
            "$ref": "#/definitions/xxxx"
          },
}
...

"definitions": {
    "xxxx": {
      "name": "X-Id",
      "example": "586e56f8ed0542d7a1521786a9d6c456",
      "in": "path",
      "required": true,
      "type": "string"
    }
}

Command line used for generation

Steps to reproduce

Related issues/PRs

Suggest a fix/enhancement

Start at DefaultCodegen.java:2574 in the stack trace and compare how the referenced parameter from the OpenAPI 2.0 demo is handled with the BodyParameter cast. Review the related calls in DefaultCodegen.java, AbstractJavaCodegen.java, and DefaultGenerator.java; done means generation completes without the ClassCastException for the referenced path parameter.