AudioSystem.mixerInfo returns 0 mixer (Java 1.3 Service compatibility)

[jpragey]

When I run the following Ceylon code :

import java.lang { ObjectArray }
import javax.sound.sampled { AudioSystem, Mixer }
hared void run() {
    ObjectArray<Mixer.Info> mixers=AudioSystem.mixerInfo;
    print("Ceylon: ``mixers.size``");
}

module org.audiotest "1.0.0" {
    import java.base "7";
    import java.desktop "7";
}

I get 0 results; however when I run the following Java code (in the same ceylon project):

package org.audiotest;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Mixer;

public class AudioTest {

    public AudioTest() {}

    public static void main(String[] args) {
        Mixer.Info[] mixers = AudioSystem.getMixerInfo();
        System.out.println("Mixers: " + mixers.length);
    }
}

I get 5 results.

I investigated it with eclipse debugger; it ended up in sun.misc.Service$LazyIterator.hasNext() loading "META-INF/services/javax.sound.sampled.spi.MixerProvider" by CeylonModuleClassLoader.getResources(), which returned an empty enumeration.

In pure java it is loaded by sun.misc.Launcher.AppClassLoader.getResources() returns 2 values.
On my PC (linux 64 / openJDK 7)
META-INF/services/javax.sound.sampled.spi.MixerProvider is in /usr/lib/jvm/java-7-openjdk-amd64/jre/lib/resources.jar.

So the PB is probably a more general Java 1.3 Service SPI and Ceylon class loading compatibility issue than a strictly java audio one.

Full project:
https://drive.google.com/file/d/0B09FzhUz_CgbMkhRenpWQXdfQ2c/edit?usp=sharing

[FroMage]

@alesj: how can we make this jar visible to the JDK class loader? What's weird is that I was pretty sure that the JDK used the JDK class loader, so it should just be visible to itself.

[quintesse]

I know that in JBoss Modules if you use their module.xml descriptor file you have to specifically import or export any services, by default it doesn't do any of that.

So even if the module can be loaded and the classes accessed you won't be able to read any of the service entries unless you import/export them. (The docs are very vague, I think "import" means available to the module itself, "export" means available to everyone).

I don't know how this affects the JDK packages though.

[AnandA777]

I know that it isn't quite the same situation, but I found a case where someone was trying to get a Java Sound service provider set up as a JBoss module:

https://community.jboss.org/thread/200423?tstart=0&_sscc=t

Does any of the info there help?

[alesj]

Afaik, we already handle services as they should be:

• https://github.com/ceylon/ceylon-runtime/blob/master/testsuite/src/test/java/org/jboss/ceylon/test/modules/services/test/ServicesTestCase.java

Imo, this here is just a case of proper visibility?

[quintesse]

What do you mean by "proper visibility"?

[alesj]

What do you mean by "proper visibility"?

It depends on what the classloader where you wanna load the services "sees".

Since I'm saying, if all is done right, the services should be loaded; see the test.

[quintesse]

Well yes, but in this case it's obvious something doesn't work, @jpragey does something very simple, that is supposed to work, using an ordinary Java class that outside of JBoss Modules works just fine. So something is wrong, right? It would be nice to figure out what exactly.

[alesj]

Try adding a test to the existing ServicesTest, which would mimic what @jpragey does.
And we can go from there.

[quintesse]

@alesj test added

[alesj]

@quintesse both cases return zero mixers ...

[quintesse]

Do you have any audio mixers in your system? ;)
The Java version should return something non-zero, otherwise there isn't anything for you to test...