Usage of META-INF.services in module?

Module Development
1

Hello,

I have a module which need to use META -INF.services.

A third party dependency need to load a class provided in the META -INF.services.

Is it possible ?

When the third party dependency try to load it, I have an exception.

I have ever tried something like this before the third party look for it.

 ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
  try{

    Thread.currentThread().setContextClassLoader(UtilsGst.class.getClassLoader());
    xxxxxxxxx

 } finally {
            Thread.currentThread().setContextClassLoader(classLoader);
 }
2

What's the Exception?

None of our modules use the ServiceLoader mechanism so I'm not able to tell you if there's something making this fundamentally impossible or not.

3

When the third party look for the class named in

com/bouyguesenergiesservices/ignition/common/videoviewer/
META-INF/org.freedesktop.gstreamer.glib.NativeObject$TypeProvider:

com.bouyguesenergiesservices.ignition.common.videoviewer.Types

it can't find it.
Stack trace:

java.lang.RuntimeException: java.lang.InstantiationException

at org.freedesktop.gstreamer.glib.NativeObject.objectFor(NativeObject.java:195)

at org.freedesktop.gstreamer.glib.Natives.objectFor(Natives.java:166)

at org.freedesktop.gstreamer.glib.Natives.callerOwnsReturn(Natives.java:140)

at org.freedesktop.gstreamer.lowlevel.GTypeMapper$2.fromNative(GTypeMapper.java:113)

at com.sun.jna.Function.invoke(Function.java:370)

at com.sun.jna.Library$Handler.invoke(Library.java:270)

at jdk.proxy3/jdk.proxy3.$Proxy123.g_value_dup_object(Unknown Source)

at org.freedesktop.gstreamer.glib.GObject.get(GObject.java:194)

...

at java.base/java.lang.Thread.run(Unknown Source)

Caused by: java.lang.InstantiationException: null

at java.base/jdk.internal.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(Unknown Source)

at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Unknown Source)

at java.base/java.lang.reflect.Constructor.newInstance(Unknown Source)

at org.freedesktop.gstreamer.glib.NativeObject.objectFor(NativeObject.java:187)

... 44 common frames omitted
4

I don't think your META-INF folder is in the correct location. It should be at the root of your JAR file.

1 Like
5

Old repo, but look at the structure here:

All of your modules provided jars should be on the same classloader, so I think this should fundamentally work.

6

seem to be ok ? or I need to put the META-INF.services at another location ???

image
image1101×474 20.3 KB

7

It's not "META-INF.services", it's "META-INF/services". Two directories.

(not sure if that's what you have or it's just the IDE showing it that way)

8

Yes that IJ showing folder in that way

9

Do you have a no-arg constructor, explicit or implicit, in your service implementation class?

10

the service implementation class:

package org.freedesktop.gstreamer.examples;

import java.util.stream.Stream;
import org.freedesktop.gstreamer.glib.NativeObject;
import org.freedesktop.gstreamer.glib.Natives;

/**
 * Custom type registration for WebRTC example. This class is registered in
 * META-INF/services to be picked up by the {@link ServiceLoader}.
 */
public class Types implements NativeObject.TypeProvider {

    @Override
    public Stream<NativeObject.TypeRegistration<?>> types() {
        return Stream.of(
                Natives.registration(WebRTCICE.class, WebRTCICE.GTYPE_NAME, WebRTCICE::new)
        );
    }

}
11

Should the file actually be called org.freedesktop.gstreamer.glib.NativeObject.TypeProvider?

since TypeProvider is a static inner class?

12

I think I've have finally something which works, but I need to understand after multiples code changes.

  • Thread.currentThread().setContextClassLoader before the initial third-party lib init in the -common
  • Thread.currentThread().setContextClassLoader before the call of the function in the -gateway

both files added:

  • org.freedesktop.gstreamer.glib.NativeObject.TypeProvider
  • org.freedesktop.gstreamer.glib.NativeObject$TypeProvider

with reference to:

  • com.bouyguesenergiesservices.ignition.common.videoviewer.Types

I will see what it's necessary.