off **building an image from scratch** as described above: [Build a Docker Image for FastAPI](#build-a-docker-image-for-fastapi).

This image would be useful mainly in the special cases described above in [Containers with Multiple Processes and Special Cases](#containers-with-multiple-processes-and-special-cases). For example, if your application is **simple enough** that setting a default number of processes based on the CPU works well, you don't want to bother with manually configuring...

    ```

!!! info
    `File` is a class that inherits directly from `Form`.

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

!!! tip
    To declare File bodies, you need to use `File`, because otherwise the parameters would be interpreted as query parameters or body (JSON) parameters.

The files will be uploaded as "form data".

github-social-preview.png...

## About "Form Fields"

The way HTML forms (`<form></form>`) sends the data to the server normally uses a "special" encoding for that data, it's different from JSON.

**FastAPI** will make sure to read that data from the right place instead of JSON.

!!! note "Technical Details"

Because this dependency function doesn't have any scope requirements itself, we can use `Depends` with `oauth2_scheme`, we don't have to use `Security` when we don't need to specify security scopes.

We also declare a special parameter of type `SecurityScopes`, imported from `fastapi.security`.

This `SecurityScopes` class is similar to `Request` (`Request` was used to get the request object directly).

common_parameters --> read_users
```

This way you write shared code once and **FastAPI** takes care of calling it for your *path operations*.

!!! check
    Notice that you don't have to create a special class and pass it somewhere to **FastAPI** to "register" it or anything similar.

    You just pass it to `Depends` and **FastAPI** knows how to do the rest.

## Share `Annotated` dependencies

We will create a `PeeweeConnectionState`:

```Python hl_lines="10-19"
{!../../../docs_src/sql_databases_peewee/sql_app/database.py!}
```

This class inherits from a special internal class used by Peewee.

It has all the logic to make Peewee use `contextvars` instead of `threading.local`.

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

!!! info
    To declare headers, you need to use `Header`, because otherwise the parameters would be interpreted as query parameters.

## Automatic conversion

* den Pfad-Parameter `item_id` mittels `Path` deklarieren
* die Parameter in einer unterschiedlichen Reihenfolge haben
* `Annotated` nicht verwenden

... dann hat Python eine kleine Spezial-Syntax für Sie.

Übergeben Sie der Funktion `*` als ersten Parameter.

    * [Dependencies - First Steps - Share `Annotated` dependencies](https://fastapi.tiangolo.com/tutorial/dependencies/#share-annotated-dependencies)

Special thanks to [@nzig](https://github.com/nzig) for the core implementation and to [@adriangb](https://github.com/adriangb) for the inspiration and idea with [Xpresso](https://github.com/adriangb/xpresso)! 🚀

### Features