问题
As far as I understand every bundle in osgi has its own classloader. Let's suppose we have three bundles:1,2,3. There is singleton class in bundle 1. Bundle 2 loads singleton and makes some changes in it. And as far as I understand, if bundle 3 loads singleton too its version of singleton is different. So Singleton in bundle 2 != singleton in bundle 3.
Are my statements right? If they are right, so it is not singleton, is it?
回答1:
It is true that each bundle has its own classloader, but the classloaders are "shared", depending on the Manifest import-package declaration. Each bundle classloader maintain a private mapping table that tells it which classloader is responsible for providing classes from a particular package.
In your case, when bundle 2 loads the singleton, it does not load the Singleton by itself, it asks the bundle 1 classloader for the class.
来源：https://stackoverflow.com/questions/37321168/can-singleton-be-implemented-in-osgi-environment