Question

Further to the question posted here: Can you find all classes in a package using reflection? I started using the Reflections library to find all classes that subclass a given type. The source code looks like this, from an answer to the linked SO question:

Reflections ref = new Reflections(new ConfigurationBuilder()
    .setScanners(new SubTypesScanner(false /* don't exclude Object.class */), new ResourcesScanner())
    .setUrls(ClasspathHelper.forPackage("org.somepackage"))
    .filterInputsBy(new FilterBuilder().include(FilterBuilder.prefix("org.somepackage"))));

ref.getSubtypesOf(Object.class);

However, after using this code obliviously for a while, I’ve just discovered that it will only find classes that subclass another type within this package. It won’t find classes that subclass externally defined classes, say from another user-defined package.

I’m not sure how to get around this using the Reflections library. I want all classes that declare their package as ‘org.somepackage’, regardless of what their supertype is. Any help?

Answer 1

I wrote a library called Rebound (as opposed to Reflections) which searches for the subclasses of a given type and package prefix. If you set the prefix empty, it will search every class under the classpath, e.g.

import gigadot.exp.reflects.core.Processor;

Rebound r = new Rebound("");
Set<Class<? extends Processor>> classes = r.getSubClassesOf(Processor.class);

But you should be careful, because searching everything in the classpath is a slow process.

The library is much simpler than Reflections and might not do what you want. I wrote this due to my frustration when I submitted my bug report but no one there tries to solve the problem.