Question

I have troubles using the java ServiceLoader in a NetBeans module application. Here is what I’m trying to do (and it works in a normal java application in Eclipse):

I have an interface.jar, which declares the interface. And I have implementations.jar, which has several implementations of this interface, all specified in the spi/META-INF/services/my.package.name.MyInteface file (this file is in the implemenations.jar).

I also have a class ImplementationHandler (in yet another handler.jar), which has the following method to load all implementations:

private static List<MyInterface<?>> loadAllImplementations() {
    List<MyInterface<?>> foundImplementations = Lists.newArrayList();
    try {
        for (MyInterface implementation : ServiceLoader.load(MyInterface.class)) {
            foundImplementations.add(implementation);
        }
    } catch (ServiceConfigurationError error) {
        system.out.println("Exception happened");
    }
    return foundImplementations;
}

This code returns all implementations in Eclipse normal application (the foundImplementations.size() > 0).

However under NetBeans, it can’t find anything (foundImplementations.size() == 0).

More details:
I have the source of a NetBeans module application (open source, not written by me), which I need to extend by using some of MyInterface implementations. The interface.jar, implementations.jar and the handler.jar are created in Eclipse and they are part of another application.

In the NetBeans, I opened the module which needs to use the new impplementations and I added all my 3 jars as external libraries (NetBeans copied them into its ext folder, which I don’t want but I can’t do anything about – I want them in another myext folder, but that’s another story). Then I rebuilt everything and tried to use one of my implementations, but it was not found… The code that gets an implementation is in the ImplementationHandler class and looks like:

public static final <T> MyInteface<T> getByName(String name) {
    for (MyInteface implementation : loadAllImplementations()) {
        if (implementation.getName().equals(name)) {
            return implementation;
        }
    }

    throw new IllegalArgumentException("Unable to find MyInterface class for: " + name);
}

I got my exception “Unable to find MyInteface class for: myImplementationName”…

My knowledge about NetBeans is very limited and I was wondering is there something more that I need to do in order to get this working?

Answer 1

I gave up, and replaced ClassLoader with JSPF. This works out of the box and I don’t need to know about the internals of a third party program, written as NetBeans module and how this affects the classpath given to the class loaders.