Pipeline

An useful feature of mediatpy is that you can build a pipeline of chained mediatpy.PipelineBehavior that will be executed, both, before and after a mediatpy.RequestHandler.

You can define any number of mediatpy.PipelineBehavior and even define some of them with a supertype to catch all of the executions of their subtypes. Moreover, you can be sure that the execution order of mediatpy.PipelineBehavior will be the expected right.

For example, MyGenericPipelineBehavior is defined before MyPipelineBehavior and it’s using mediatpy.Request instead of MyRequest in their definition, so it will be executed for mediatpy.Request and for all their subtypes as MyRequest.

Example

import asyncio
from typing import Callable, Awaitable

from mediatpy import Request, RequestHandler, Mediator, PipelineBehavior


class MyResponse:
    ...


class MyRequest(Request[MyResponse]):
    ...


mediator = Mediator()


@mediator.request_handler
class MyRequestHandler(RequestHandler[MyRequest, MyResponse]):
    async def handle(self, request: MyRequest) -> MyResponse:
        print(self.__class__.__name__)
        return MyResponse()


@mediator.pipeline_behavior
class MyGenericPipelineBehavior(PipelineBehavior[Request, MyResponse]):  # Request instead of MyRequest
    async def handle(self, request: MyRequest, next_behavior: Callable[..., Awaitable[MyResponse]]) -> MyResponse:
        print(f"Before {self.__class__.__name__}")
        response = await next_behavior()
        print(f"After {self.__class__.__name__}")
        return response


@mediator.pipeline_behavior
class MyPipelineBehavior(PipelineBehavior[MyRequest, MyResponse]):
    async def handle(self, request: MyRequest, next_behavior: Callable[..., Awaitable[MyResponse]]) -> MyResponse:
        print(f"Before {self.__class__.__name__}")
        response = await next_behavior()
        print(f"After {self.__class__.__name__}")
        return response

async def main():
    request = MyRequest()
    await mediator.send(request)


if __name__ == '__main__':
    asyncio.run(main())

# Before MyGenericPipelineBehavior
# Before MyPipelineBehavior
# MyRequestHandler
# After MyPipelineBehavior
# After MyGenericPipelineBehavior