Question

I am working with SpringData’s Neo4j graph DB hello-worlds example and I ran across the following code in WorldRepositoriesImpl.java…

@Autowired private WorldRepository worldRepository;

Furthermore, WorldRepository is defined as…

public interface WorldRepository extends MyWorldRepository, 
                                         GraphRepository<World>,
                                         NamedIndexRepository<World> 
{/* no method defined here */}

Now the odd part, no class that I can find actually implements WorldRepository.So, a few questions…

How is this possible? Where is this documented? Is there a way to make this a bit more explicit (less mysterious)?

Answer 1

Running the code with a debugger attached shows that the worldRepository instance wired up by Spring is a proxy object created at runtime.

Looking at the pom.xml and the dependencies included, it looks like the spring-neo4j library bundles in some Aspects that create this implementation class at runtime.

In other words, there is no implementation of this interface declared in the source code – but one is created at runtime with AspectJ and other tools.