Question

I have a class in Java, I wish to reflect all subclasses of this class, how would I do this?

In this specific case, all subclasses are in the same package, and only subclasses are in this package, so an equivalent solution is to fetch all classes in a package.

Answer 1

I think you could do this using spring’s org.springframework.core.io.support.PathMatchingResourcePatternResolver. At least I know you can use it to find all classes with a certain annotation. Finding subclasses seems to be a very similar problem I’d expect to work as well.

Here’s some (untested) code to get you started:

PathMatchingResourcePatternResolver match = new PathMatchingResourcePatternResolver();
MetadataReaderFactory f = new SimpleMetadataReaderFactory();
List<Class<?>> matches = ...;
for (Resource r : match.getResources("classpath*:com/example/**/*.class")) {
    AnnotationMetadata meta = f.getMetadataReader(r).getAnnotationMetadata();
    if (meta.getAnnotationsTypes().contains(MyAnnotation.class.getName()) {
        matches.add(Class.forName(meta.getClassName()));
    }
}
return matches;

As you might see, it’s basically the idea describe by Stephen C