What does OSGi solve?

Question

I\'ve read on Wikipedia and other sites about OSGi, but I don\'t really see the big picture. It says that it\'s a component-based platform, and that you can reload modules a

Answer 1

A Few Things that drive me nuts on OSGi:

1) The implentations and their context loaders have a lot of quirks to them, and can be somewhat async (We use felix inside of confluence). Compared to a pure spring (no DM) where [main] is pretty much running through everything sync.

2)Classes are not equal after a hot load. Say, for instance you have a tangosol cache layer on hibernate. It is filled with Fork.class, outside of the OSGi scope. You hotload a new jar, and Fork has not changed. Class[Fork] != Class[Fork]. It also appears during serialization, for the same underlying causes.

3)Clustering.

You can work around these things, but it is a major major pain, and makes your architecture look flawed.

And to those of you advertising the hotplugging.. OSGi's #1 Client? Eclipse. What does Eclipse do after loading the bundle?

It restarts.

Answer 2

At the very least, OSGi makes you THINK about modularity, code reuse, versioning and in general the plumbing of a project.

Answer 3

The OSGi provides following benefit:

■ A portable and secure execution environment based on Java

■ A service management system, which can be used to register and share services across bundles and decouple service providers from service consumers

■ A dynamic module system, which can be used to dynamically install and uninstall Java modules, which OSGi calls bundles

■ A lightweight and scalable solution