When MessageHandlers are registered with the MessageBus, the bus assigns the handler to a dispatcher based on the provided schedule as described above. Internally, the bus is creating and registering an instance that implements the MessageEndpoint interface. This is where other handler metadata enters the picture (e.g. the concurrency settings). Basically, you can consider the endpoint to be a composite handler built from a simple implementation of the MessageHandler along with its metadata. In fact, the MessageEndpoint does extend the MessageHandler interface.

public interface MessageEndpoint extends MessageHandler {
    String getName();
    Subscription getSubscription();
    ConcurrencyPolicy getConcurrencyPolicy();
}

When using the API, it's simpler to register handlers with metadata and leave the message endpoint as an internal responsibility of the bus. However, it is possible to create endpoints directly. Spring Integration provides a single implementation: DefaultMessageEndpoint.