def post(self, request: Request) -> None:
"""
Dispatches a request over middleware. Returns when message put onto outgoing channel by producer,
does not wait for response from a consuming application i.e. is fire-and-forget
:param request: The request to dispatch
:return: None
"""
if self._producer is None:
raise ConfigurationException("Command Processor requires a Producer to post to a Broker")
if self._message_mapper_registry is None:
raise ConfigurationException("Command Processor requires a Message Mapper Registry to post to a Broker")
message_mapper= self._message_mapper_registry.lookup(request)
message = message_mapper(request)
self._message_store.add(message)
self._producer.send(message)
def send(self, request):
"""
Dispatches a request. Expects one and one only target handler
:param request: The request to dispatch
:return: None, will throw a ConfigurationException if more than one handler factor is registered for the command
"""
handler_factories = self._registry.lookup(request)
if len(handler_factories) != 1:
raise ConfigurationException("There is no handler registered for this request")
handler = handler_factories[0]()
handler.handle(request)
def register(self, request_class: Request,
mapper_func: Callable[[Request], BrightsideMessage]) -> None:
"""Adds a message mapper to a factory, using the requests key
:param mapper_func: A callback that creates a BrightsideMessage from a Request
:param request_class: A request type
"""
key = request_class.__name__
if key not in self._registry:
self._registry[key] = mapper_func
else:
raise ConfigurationException(
"There is already a message mapper defined for this key; there can be only one"
)
def lookup(self, request_class: Request) -> Callable[[Request], Message]:
"""
Looks up the message mapper function associated with this class. Function should take in a Request derived class
and return a Message derived class, for sending on the wire
:param request_class:
:return:
"""
key = request_class.__class__.__name__
if key not in self._registry:
raise ConfigurationException(
"There is no message mapper associated with this key; we require a mapper"
)
else:
return self._registry[key]
def lookup(self, request: Request) -> List[Callable[[], Handler]]:
"""
Looks up the handler associated with a request - matches the key on the request to a registered handler
:param request: The request we want to find a handler for
:return:
"""
key = request.__class__.__name__
if key not in self._registry:
if request.is_command():
raise ConfigurationException(
"There is no handler registered for this request")
elif request.is_event():
return [] # type: Callable[[] Handler]
return self._registry[key]
def lookup(self, request):
"""
Looks up the handler associated with a request - matches the key on the request to a registered handler
:param request: The request we want to find a handler for
:return:
"""
key = request.key
if key not in self._registry:
if request.is_command():
raise ConfigurationException(
"There is no handler registered for this request")
elif request.is_event():
return []
return self._registry[key]
def register(self, request, handler_factory):
"""
Register the handler for the command
:param request: The command or event to dispatch. It must implement getKey()
:param handler_factory: A factory method to create the handler to dispatch to
:return:
"""
key = request.key
is_command = request.is_command()
is_event = request.is_event()
is_present = key in self._registry
if is_command and is_present:
raise ConfigurationException(
"A handler for this request has already been registered")
elif is_event and is_present:
self._registry[key].append(handler_factory)
elif is_command or is_event:
self._registry[key] = [handler_factory]
