I understand that a service is an interface defining what functions are to be implemented.
I also understand that a service provider implements these functions.
However, I can't seem to understand what a service provider interface is. Would I be correct in saying it is an interface which defines a method to instantiate the service?
Baeldung has an answer to your question in his article: Java Service Provider Interface:
Service Provider Interface
An interface or abstract class that acts as a proxy or an endpoint to the service.
If the service is one interface, then it is the same as a service provider interface.
Service and SPI together are well-known in the Java Ecosystem as API.
