Only thing I might add is to mention the use of the @Named annotation. It’s one way to bind the same interface or class to different implementations. Here’s a contrived example that injects different JPA EntityManagerFactories :

class FooDaoFactory {
def entityManagerFactory;

@Inject
public FooDaoFactory(@Named(“persist-unit-foo”) EntityManagerFactory entityManagerFactory) {
this.entityManagerFactory = entityManagerFactory;

}
}

class BarDaoFactory {
def entityManagerFactory;

@Inject
public BarDaoFactory(@Named(“persist-unit-bar”) EntityManagerFactory entityManagerFactory) {
this.entityManagerFactory = entityManagerFactory;

}
}

binder.bind(EntityManagerFactory.class).annotatedWith(Names.named(“persist-unit-foo”)).toInstance(Persistence.createEntityManagerFactory(“fooUnit”));

binder.bind(EntityManagerFactory.class).annotatedWith(Names.named(“persist-unit-bar”)).toInstance(Persistence.createEntityManagerFactory(“barUnit”));

def injector = Guice.createInjector()
def foo = injector.getInstance(FooDaoFactory.class);
def bar = injector.getInstance(BarDaoFactory.class);

Nice introduction for Groovy.
Are you planning to use Guice in your next projects?