I know that there's a tool that is able to do an online validation:
http://online.swagger.io/validator?url=http://petstore.swagger.io/v2/swagger.json
I'm writing a JUnit test that validates the project's swagger.json file. It's important that this validation can be done offline, because the test runs as localhost, and that validation tool can't reach a localhost server.
So, is it possible to validate a Swagger 2.0 JSON file, offline?