Can you find all classes in a package using reflection?

Question

Is it possible to find all classes or interfaces in a given package? (Quickly looking at e.g. Package, it would seem like no.)

Answer 1

You should probably take a look at the open source Reflections library. With it you can easily achieve what you want.

First, setup the reflections index (it's a bit messy since searching for all classes is disabled by default):

List classLoadersList = new LinkedList();
classLoadersList.add(ClasspathHelper.contextClassLoader());
classLoadersList.add(ClasspathHelper.staticClassLoader());

Reflections reflections = new Reflections(new ConfigurationBuilder()
    .setScanners(new SubTypesScanner(false /* don't exclude Object.class */), new ResourcesScanner())
    .setUrls(ClasspathHelper.forClassLoader(classLoadersList.toArray(new ClassLoader[0])))
    .filterInputsBy(new FilterBuilder().include(FilterBuilder.prefix("org.your.package"))));

Then you can query for all objects in a given package:

Set> classes = reflections.getSubTypesOf(Object.class);