OSGI service vs. Singleton?

Question

I am a beginner to OSGI and I am wondering if someone can enlighten me about the difference between creating OSGI service vs singleton pattern. For example, suppose I have a bundle core which provides IService, and multiple bundles that needs to access this. I can:

1. register a service in the core-bundle, in which the plugins can access
2. provide a singleton class, which provides the service

Using OSGI service seems to be quite cumbersome; and since the plugins have to depend on Core anyways (to get the interface), what's the advantage of using OSGI service?

Answer 1

You can manage the life cycle (deploy new version of the service, concurrently run multiple versions etc) of a service but you can't manage the life cycle of singleton without restarting the JVM (even with restart you can just have 1 version available at any point of time).