title: OSGI service vs. Singleton?
body: <p>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 <code>core</code> which provides <code>IService</code>, and multiple bundles that needs to access this.  I can:</p>
  
  <ol>
  <li>register a service in the <code>core</code>-bundle, in which the plugins can access</li>
  <li>provide a singleton class, which provides the service</li>
  </ol>
  
  <p>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?</p>