Migrated attachment for Guice issue 805, comment 1

RobotLegs.java

import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.PrivateModule;

import javax.inject.Inject;
import java.lang.annotation.Annotation;

import static com.google.inject.name.Names.named;
import static java.lang.String.format;

public class RobotLegs
{
    private static final String leftName = "lefty";
    private static final String rightName = "righty";
    private static final Annotation leftAnnotation = named(leftName);
    //private static final Annotation rightAnnotation = named(rightName);
    private static final Annotation rightAnnotation = null;
    private static Key<Leg> leftKey = Key.get(Leg.class, leftAnnotation);
    //private static Key<Leg> rightKey = Key.get(Leg.class, rightAnnotation);
    private static Key<Leg> rightKey = Key.get(Leg.class);

    public static void main(String[] args)
    {
        Injector injector = Guice.createInjector(
                new AnnotatedLegModule(leftName, leftAnnotation),
                new AnnotatedLegModule(rightName, rightAnnotation));

        Leg leftLeg = injector.getInstance(leftKey);
        Leg rightLeg = injector.getInstance(rightKey);
        System.out.println(format("left=%s foot=%s (%s)", leftLeg, leftLeg.foot, leftLeg.foot.side));
        System.out.println(format("right=%s foot=%s (%s)", rightLeg, rightLeg.foot, rightLeg.foot.side));
    }

    public static class AnnotatedLegModule extends PrivateModule
    {
        private final String side;
        private final Annotation annotation;

        public AnnotatedLegModule(String side, Annotation annotation)
        {
            this.side = side;
            this.annotation = annotation;
        }

        @Override
        protected void configure()
        {
            bind(Foot.class).toInstance(new Foot(side));
            if (annotation != null) {
                bind(Leg.class).annotatedWith(annotation).to(Leg.class);
                expose(Leg.class).annotatedWith(annotation);
            }
            else {
                bind(Leg.class);
                expose(Leg.class);
            }
        }
    }

    public static class Leg
    {
        public final Foot foot;

        @Inject
        public Leg(Foot foot)
        {
            this.foot = foot;
        }
    }

    public static class Foot
    {
        public final String side;

        @Inject
        public Foot(String side)
        {
            this.side = side;
        }
    }
}