what is the relation between package and bundle version in OSGi

Question

In OSGi bundles packages are exported and imported with a version number. Still bundles have a version defined. This seems redundant to me.

What is the point of versioning both the bundle and the packages contained in it? I understand that bundles/jars might be versioned for using it in non-OSGi systems (for maven, for example). Is there any other reason for this?

I am a bit confused about these two levels of versioning. Are these two version numbers dependent or independent to the package versions they contain? If dependent, what are the rules to version the bundle?

Answer 1

In OSGi, packages define the contracts that are used to let bundles collaborate. Bundles are JARs that hold the code.

• The purpose of a package version is to make sure that bundles only depend/use contracts that they are compatible with. Packages use semantic versioning to signal minor, micro, and major changes. A bundle can export and import any number of packages and does provide and consume any number of contracts.
• The purpose of a bundle version is to have a unique identifier for each JAR so it can be handled during the development life cycle. A SHA code would work as well but would be less convenient. Some organizations bump the bundle version based on the highest change in any of its packages. I.e. if its contained packages only had minor changes,the bundle would be bumped with a minor change. If one package had a major change, the bundle would be bumpled major.