Java generator produces invalid code when discriminator object names contain underscore

[DaveChamberlinKidd]

Description

In v2.4.0 a change was made which automatically populated the discriminator variable
with the class name. However whilst the variable name was converted from the model to
a java friendly variable, for example object_type to objectType in the parent class
the set variable didn't translate accordingly and so leaves uncompilable code.

As a result the generated code produced was...

  public ParentObject() {
    this.object_type = this.getClass().getSimpleName();
  }
  public ParentObject objectType(String objectType) {
    this.objectType = objectType;
    return this;
  }

and not

    this.objectType = this.getClass().getSimpleName();

There is a workaround which is that you specify your discriminator as the camel case version of the object but I assume this only works for the Java generator (and other generators that use camel case) it stops the swagger specification from being language independent.

Swagger-codegen version

v2.4.0+

Swagger declaration file content or url

swagger: '2.0'
info:
  description: Demo error
  version: 1.0.0
  title: Demo
host: flamangoes.co.uk
schemes:
  - https
consumes:
  - text/xml
produces:
  - application/json
paths:
  /v1/demo:
    post:
      summary: Demo
      parameters: []
      responses:
        '404':
          schema:
            type: array
            items:
              $ref: '#/definitions/Parent_Object'
definitions:
  Parent_Object:
    type: object
    required:
      - object_type
      - type
    discriminator: object_type
    properties:
      object_type:
        type: string
  Child_Object:
    type: object
    allOf:
      - $ref: '#/definitions/Parent_Object'
      - {}
      - {}

Command line used for generation

swagger-codegen generate -i -l java

Steps to reproduce

Run the Java code gen

Related issues/PRs

Issue was cause by commit 73c338b

Suggest a fix/enhancement

I've taken a fork of the project and have a fix that works, but as I don't know the codebase it may not be how you would want to fix it. I'll raise a PR so someone can take a look