Class-Based Handlers for AIOHTTP

Class-based handlers in Wireup provide a new mechanism for efficient dependency injection for AIOHTTP applications. They optimize performance by managing dependencies at startup rather than per request. Dependencies injected in the init method are zero-cost.

Key Benefits

• Request Performance: Zero overhead from dependency resolution during request handling.
• Stateful Handlers: Maintain state across requests.
• Route set: Group relevant resource endpoints together

Example

greeter.py

class GreeterHandler:
    router = web.RouteTableDef()  # (1)!

    def __init__(self, greeter: GreeterService) -> None:  # (2)!
        self.greeter = greeter
        self.counter = 0

    @router.get("/greet")
    async def get_thing(
        self,
        request: web.Request,  # (3)!
        auth_service: Injected[AuthenticationService],  # (4)!
    ) -> web.Response:
        self.counter += 1

        return web.json_response(
            {
                "greeting": self.greeter.greet(
                    request.query.get("name", "world")
                ),
                "counter": self.counter,
            }
        )

1. The class must contain a web.RouteTableDef instance named router. Use it to decorate routes inside this class.
2. When injecting in the constructor the Injected syntax is not required.
3. Like every AIOHTTP request handler, the first argument must be web.Request.
4. Other scoped/transient dependencies can be requested in the routes. Here the Injected[T] annotation is required.

app.py

wireup.integration.aiohttp.setup(container, app, handlers=[GreeterHandler])

Overriding: Handlers are created once on startup, their dependencies cannot be overridden once the application starts. If you need to override dependencies in the handler's __init__, then it must be done before application startup.