Find all the classes inside a package in Java without reflection

Question

I am trying to find all the classes defined inside a package. I have tried this code -

public static File[] getPackageContent(String packageName) throws IOException{
    ArrayList<File> list = new ArrayList<File>();
    Enumeration<URL> urls = Thread.currentThread().getContextClassLoader().getResources(packageName);
    while (urls.hasMoreElements()) {
        URL url = urls.nextElement();
        File dir = new File(url.getFile());
        for (File f : dir.listFiles()) {
            list.add(f);
        }
    }
    return list.toArray(new File[]{});

Now here is the thing - if the String packageName does not contain "." character, it returns me all the names of the classes which I want exactly. But suppose if the packageName contains "." character it does not return anything.

Why is that? If possible how can I find all the classes inside a package where the package name does have a "." character in it?

please give examples of what you mean by package name with a . in it? — Tschallacka, Dec 23 '15 at 16:20
This question is resolved in this thread [Can you find all classes in a package using reflection?](http://stackoverflow.com/questions/520328/can-you-find-all-classes-in-a-package-using-reflection) — viticlick, Dec 23 '15 at 16:22
I concur with Thiago, internal class names as known by the class loaders use `/` instead of `.` for package separator — Aaron, Dec 23 '15 at 16:22
Perfect. I replaced "." character with "/" and its working like a charm. Thanks Thiago and Aaron. — Aritro Sen, Dec 23 '15 at 16:27
I don't think this is a duplicate. He's not using reflection and the answer to the supposedly duplicated question starts with "(...) this is not possible", which is clearly not the case. — Fred Porciúncula, Dec 23 '15 at 16:30
that works as long as you don't generate a java executable (`jar`) — toto_tico, May 08 '16 at 00:36

score 1 · Answer 1 · answered Dec 23 '15 at 16:27

You could use Reflections:

    private Class<?>[] scanForTasks(String packageStr) {
        Reflections reflections = new Reflections((new ConfigurationBuilder()).setScanners(new Scanner[]{new SubTypesScanner(), new TypeAnnotationsScanner()}).setUrls(ClasspathHelper.forPackage(packageStr, new ClassLoader[0])).filterInputsBy((new FilterBuilder()).includePackage(packageStr)));
        Set classes = reflections.getTypesAnnotatedWith(Task.class);
        Class[] taskArray = (Class[])classes.toArray(new Class[classes.size()]);
        return taskArray;
    }
}

Since the question has been edited to ask about doing this without reflection, your answer isn't applicable anymore. — azurefrog, Dec 23 '15 at 18:47

Find all the classes inside a package in Java without reflection

1 Answers1