TestCorsHandler handler1 = new TestCorsHandler("handler1");
        TestCorsHandler handler2 = new TestCorsHandler("handler2");
        TestCorsHandler handler3 = new TestCorsHandler("handler3");

        // Execute
        corsHandlerFactory.add(origin1, handler1);
        corsHandlerFactory.add(origin2, handler2);
        corsHandlerFactory.add(origin3, handler3);

        // Verify

Bir request geçersiz veri içerdiğinde, **FastAPI** içeride `RequestValidationError` raise eder.

Ve bunun için varsayılan bir exception handler da içerir.

Override etmek için `RequestValidationError`’ı import edin ve exception handler’ı `@app.exception_handler(RequestValidationError)` ile decorate edin.

Exception handler, bir `Request` ve exception’ı alır.

{* ../../docs_src/handling_errors/tutorial004_py310.py hl[2,14:19] *}

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

    Note over client,operation: Can raise exceptions, including HTTPException
    client ->> dep: Start request
    Note over dep: Run code up to yield
    opt raise Exception
        dep -->> handler: Raise Exception

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

    Note over client,operation: Can raise exceptions, including HTTPException
    client ->> dep: Start request
    Note over dep: Run code up to yield
    opt raise Exception
        dep -->> handler: Raise Exception

## Bir exception handler içinde request body'ye erişme { #accessing-the-request-body-in-an-exception-handler }

/// tip | İpucu

Aynı problemi çözmek için, muhtemelen `RequestValidationError` için özel bir handler içinde `body` kullanmak çok daha kolaydır ([Hataları Ele Alma](../tutorial/handling-errors.md#use-the-requestvalidationerror-body)).

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

    Note over client,operation: Can raise exceptions, including HTTPException
    client ->> dep: Start request
    Note over dep: Run code up to yield
    opt raise Exception
        dep -->> handler: Raise Exception

        // Mock Postbox - no need to mock, the framework will handle it

        // Register components
        ComponentUtil.register(searchEngineClient, "searchEngineClient");
        ComponentUtil.register(systemHelper, "systemHelper");
        ComponentUtil.setFessConfig(fessConfig);
        ComponentUtil.register(notificationHelper, "notificationHelper");
        // Postbox is handled by the framework

        // Execute

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

    Note over client,operation: Can raise exceptions, including HTTPException
    client ->> dep: Start request
    Note over dep: Run code up to yield
    opt raise Exception
        dep -->> handler: Raise Exception

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

    Note over client,operation: Can raise exceptions, including HTTPException
    client ->> dep: Start request
    Note over dep: Run code up to yield
    opt raise Exception
        dep -->> handler: Raise Exception

        """
        Run any `.on_startup` event handlers.

        This method is kept for backward compatibility after Starlette removed
        support for on_startup/on_shutdown handlers.

        Ref: https://github.com/Kludex/starlette/pull/3117
        """
        for handler in self.on_startup:
            if is_async_callable(handler):
                await handler()
            else:
                handler()