Dispatcher API

Ice::Object Base Class

For historical reasons, the Dispatcher abstraction does not correspond to a Dispatcher abstract base class in C++. We use instead the base class Ice::Object as the dispatcher base class.

Object is a concrete class that implements the pseudo Slice interface Object:

CPP

namespace Ice
{
    class Object
    {
    public:
        virtual void dispatch(
            IncomingRequest& request, 
            std::function<void(OutgoingResponse)> sendResponse);
        ...
    };
}

The implementation of dispatch on Ice::Object dispatches an incoming request to the 4 operations defined on Object: ice_id, ice_ids, ice_isA, and ice_ping. It throws OperationNotExistException for any other operation.

This implementation is immaterial: in practice, a dispatcher is any C++ class derived from Ice::Objectthat reimplements dispatch. This dispatcher may (but does not need to) implement the 4 operations defined on Object.

Servants

In C++, a servant is a concrete class that implements the Dispatcher abstraction by itself, without delegating to some other object. In other words, a servant is a “terminal dispatcher”. The base class for all C++ servants is Ice::Object. A servant should generally handle the 4 operations defined on the pseudo-Slice interface Object.

The most common type of C++ servants are classes that implement skeleton classes generated by the Slice compiler. These generated skeleton classes reimplement dispatch by:

unmarshaling input parameters
calling the pure virtual member function whose name matches the operation name carried by the request (you implement this pure virtual function in the servant class)
creating a response from the return value and out parameters returned by this function

They also implement or reimplement the 4 operations defined on Object.