Issue:

Java domain classes generated using swagger-codegen don't extend their base classes.

Solution:

http://swagger.io/specification/ - please see "Composition and Inheritance (Polymorphism)" part.

Here's an example of required changes to thomson-reuters-world-check-one-api.v1.yaml file in order to fix NewCase model - which extends UpdateCase model - generation (please note that NewCase isn't the only model with the issue):

  #
  # Definitions for Case domain
  # ===========================
  #


  UpdateCase:
    type: object
    discriminator: updateCaseType # <---- new
    description: |
      Defines Case data that can be sent when updating a Case.
  
  # ... omitting some code here

  # ...
  # UpdateCase definition continued:

  required:
    - name
    - updateCaseType # <---- new
    - providerTypes
  properties:
  
  ...

P.S.: I'm not a Swagger expert, so there might be a reason why you have missing discriminator property, but changes above helped me to generate correct java classes.