Swagger Validator

This handler is part of the light-rest-4j which is built on top of light-4j but focused on RESTful API only.

It encourages design driven implementation so swagger specification should be done before the implementation starts. With the light-codegen light-4j generator, the server stub can be generated and start running within minutes. However, we cannot rely on generator for validation as specification will be changed along the life cycle of the API. This is why we have provided a validator that works on top of the specification at runtime. In this way, the generator should only be used once and the validator will take the latest specification and validate according the specification at runtime.

Fail fast

As you may noticed that our Status object only supports one code and message. This is the indication the framework validation is designed as fail fast. Whenever there is an error, the server will stop processing the request and return the error to the consumer immediately. There are two reasons on this design:

  1. Security - you don’t want to return so many errors if someone is trying to hack your server.
  2. Performance - you don’t want to spend resource to handle invalid request to the next step.


This is the entry point of the validator and it is injected during server start up if validator.yml enableValidator is true. By default, only RequestValidator will be called. However, ResponseValidator can be enabled by setting enableResponseValidator to true in validator.yml.


It will validate the following:

  • uri
  • method
  • header
  • query parameters
  • path parameters
  • body if available

When necessary, json-schema-validator will be called to do json schema validation.


It will validate the following:

  • header
  • response code
  • body if available

when necessary, json-schema-validator will be called.


If schema is defined in swagger.json, then the json-schema-validator will be called to validate the input against a json schema defined in draft v4.


In order to test validator, the test suite starts a light-4j server and serves petstore api for testing. It is a demo on how to unit test your API during development.