Migrated attachment for Guice issue 802, comment 0

InjectorListenerWithSingletons.java

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

import com.google.inject.AbstractModule;
import com.google.inject.BindingAnnotation;
import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.Singleton;
import com.google.inject.Stage;
import com.google.inject.TypeLiteral;
import com.google.inject.matcher.Matchers;
import com.google.inject.spi.InjectionListener;
import com.google.inject.spi.TypeEncounter;
import com.google.inject.spi.TypeListener;

public class InjectorListenerWithSingletons
{
    private static final Key<IFace> KEY_1 = Key.get( IFace.class, Ann1.class );
    private static final Key<IFace> KEY_2 = Key.get( IFace.class, Ann2.class );
    
    @Retention( RetentionPolicy.RUNTIME )
    @BindingAnnotation
    public static @interface Ann1 {}
    
    @Retention( RetentionPolicy.RUNTIME )
    @BindingAnnotation
    public static @interface Ann2 {}
    
    public static interface IFace {}
    
    public static final class Impl implements IFace {}

    public static final class IModule extends AbstractModule
    {
        @Override
        protected void configure()
        {
            bind( KEY_1 ).to( Impl.class ).in( Singleton.class );
            bind( KEY_2 ).to( Impl.class ).in( Singleton.class );
        }
    }

    public static final class ListenerModule extends AbstractModule implements TypeListener
    {
        @Override
        protected void configure()
        {
            bindListener( Matchers.any(), this );
        }

        @Override
        public <I> void hear( TypeLiteral<I> type, TypeEncounter<I> encounter )
        {
            final Provider<IFace> p1 = encounter.getProvider( KEY_1 );
            final Provider<IFace> p2 = encounter.getProvider( KEY_2 );
            encounter.register( new InjectionListener<I>()
            {
                @Override
                public void afterInjection( I injectee )
                {
                    p1.get(); // if either or both of these lines are commented,
                    p2.get(); // then the test passes.
                }
            } );
        }
    }
    
    public static void main( String[] args )
    {
        Injector bindingsOnly = Guice.createInjector( Stage.PRODUCTION, new IModule() );
        assertInstances( bindingsOnly ); // successful, 
        
        Injector bindingsWithListener = Guice.createInjector( Stage.PRODUCTION, new IModule(), new ListenerModule() );
        assertInstances( bindingsWithListener ); // fails if both instances are retrieved within afterInjection()
    }

    private static void assertInstances( Injector i )
    {
        assert i.getInstance( KEY_1 ) == i.getInstance( KEY_1 ) : "KEY_1 should be a singleton";
        assert i.getInstance( KEY_2 ) == i.getInstance( KEY_2 ) : "KEY_2 should be a singleton";
        assert i.getInstance( KEY_1 ) != i.getInstance( KEY_2 ) : "KEY_1 and KEY_2 should be different";
    }
}