Using the Resource Owner Password Credentials grant type as an approach for OAuth 2.0 migration

This recipe will show you how to configure the Resource Owner Password Credentials, or Password Credentials for short. Although this grant type should be avoided at any cost, because by using it we are asking for the user's credentials (and that's what OAuth 2.0 wants to solve by the user's access delegation), it's important to mention this recipe as a strategy when migrating from a user's credential sharing approach to the OAuth 2.0 approach. In addition, it might be used safely when both the client and the OAuth 2.0 Provider belong to the same solution.

Getting ready

To run this recipe, you can use your preferred IDE and must have Java 8 and Maven installed. It's also recommended to have CURL or Postman installed, because we will interact with the Authorization Server and Resource Server automatically without actually using any client. By running this recipe, your OAuth 2.0 Provider will be able...