Annotations present at compile time but absent at runtime

It 开发者_开发知识库is possible to use Java class files which includes annotations that are not present at runtime?

Example: I want to write a class with the JPA @Embeddable annotation, which would be present at compile time (maven scope: "provided"). But the annoatation definition could be absent at runtime, if the class is used outside a JPA application.

You would have to either:

1. Swap compiled classes at runtime (to include a class without the annotation.)
2. Override the class definition of @Embeddable and remove @Retention(RUNTIME)
3. Just prevent the class itself from being scanned by your JPA provider.

OSGi applications, for example Eclipse, will ignore annotations which aren't accessible, i.e. you won't get ClassNotFoundExceptions if you have a JPA annotation without the JPA api loaded.

For this particular problem I would simply define ORM mappings in XML resources instead of annotations. These mappings could be put in a different artifact (JAR) which would be added (or not) to the classpath depending on whether you use JPA or not.