@Override
    public final Boolean call() throws Exception {
        return dispatch(handler).get();
    }
Constructs a new instances of this class over the given {@link ResponseHandler}. Invoking {@link #call()} will
dispatch to this handler.

@param handler The ResponseHandler to dispatch to.
jdisc_core/src/main/java/com/yahoo/jdisc/handler/CallableResponseDispatch.java