* Then it returns the **response**.

!!! note "Technical Details"
    If you have dependencies with `yield`, the exit code will run *after* the middleware.

    If there were any background tasks (documented later), they will run *after* all the middleware.

## Create a middleware

To create a middleware you use the decorator `@app.middleware("http")` on top of a function.

The middleware function receives:

* The `request`.

            max_length=max_length,
            discriminator=discriminator,
            multiple_of=multiple_of,
            allow_nan=allow_inf_nan,
            max_digits=max_digits,
            decimal_places=decimal_places,
            **extra,
        )
        if examples is not None:
            kwargs["examples"] = examples
        if regex is not None:
            warnings.warn(

    And Pydantic's `Field` returns an instance of `FieldInfo` as well.

    `Body` also returns objects of a subclass of `FieldInfo` directly. And there are others you will see later that are subclasses of the `Body` class.

    Remember that when you import `Query`, `Path`, and others from `fastapi`, those are actually functions that return special classes.

!!! tip

## Que signifie le déploiement

**Déployer** une application signifie effectuer les étapes nécessaires pour la rendre **disponible pour les
utilisateurs**.

Pour une **API Web**, cela implique normalement de la placer sur une **machine distante**, avec un **programme serveur**
qui offre de bonnes performances, une bonne stabilité, _etc._, afin que vos **utilisateurs** puissent **accéder** à
l'application efficacement et sans interruption ni problème.

        Doc(
            """
            Maximum number of allow digits for strings.
            """
        ),
    ] = _Unset,
    decimal_places: Annotated[
        Union[int, None],
        Doc(
            """
            Maximum number of decimal places allowed for numbers.
            """
        ),
    ] = _Unset,
    examples: Annotated[
        Optional[List[Any]],
        Doc(

dependencies and the dependencies are solved based on the declared types. So, it's not possible to declare more than one "component" that provides a certain type.

Routes are declared in a single place, using functions declared in other places (instead of using decorators that can be placed right on top of the function that handles the endpoint). This is closer to how Django does it than to how Flask (and Starlette) does it. It separates in the code things that are relatively tightly coupled....

    Gardez à l'esprit que vous devez renvoyer directement `JSONResponse`.

!!! info
    La clé `model` ne fait pas partie d'OpenAPI.

    **FastAPI** prendra le modèle Pydantic à partir de là, générera le `JSON Schema` et le placera au bon endroit.

    Le bon endroit est :

    * Dans la clé `content`, qui a pour valeur un autre objet JSON (`dict`) qui contient :

```Python hl_lines="8"
{!../../../docs_src/first_steps/tutorial001.py!}
```

You can return a `dict`, `list`, singular values as `str`, `int`, etc.

You can also return Pydantic models (you'll see more about that later).

There are many other objects and models that will be automatically converted to JSON (including ORMs, etc). Try using your favorite ones, it's highly probable that they are already supported.

## Recap

### Return a Response Directly

The most common case would be [returning a Response directly as explained later in the advanced docs](../advanced/response-directly.md){.internal-link target=_blank}.

```Python hl_lines="8  10-11"
{!> ../../../docs_src/response_model/tutorial003_02.py!}
```

## Dependencies for groups of *path operations*