java - What's the point of package annotations?

Question

I understand the purpose of class annotations, thanks to How and where are Annotations used in Java?. What is the purpose of package annotations, as described in this blog post and §7.4.1 of the Java Language Specification?

Why would you want to associate metadata with a package? What kinds of things could you do?

Answer 1

1. bnd tool (and maven-bundle-plugin) makes use of package annotations. Putting @Version and @Export annotation in package-info.java allows it to generate OSGi metadata.
2. javadoc uses package annotations.
3. JAXB uses package-level annotations, for example, to specify mapping of a Java type to XML Schema type package-wide. Package annotations are also used in JBoss's xml binding.
4. Struts 2 Convention plugin uses an annotation to specify a default interceptor for all actions in a package.
5. There are some package-level Hibernate Annotations. An example of those annotations' usage can be found here.