A middleware doesn't have to be made for FastAPI or Starlette to work, as long as it follows the ASGI spec.

In general, ASGI middlewares are classes that expect to receive an ASGI app as the first argument.

So, in the documentation for third-party ASGI middlewares they will probably tell you to do something like:

```Python
from unicorn import UnicornMiddleware

app = SomeASGIApp()

!!! danger
    Never store the plain password of a user or send it in a response like this, unless you know all the caveats and you know what you are doing.

## Add an output model

We can instead create an input model with the plaintext password and an output model without it:

=== "Python 3.10+"

    ```Python hl_lines="9  11  16"
    {!> ../../../docs_src/response_model/tutorial003_py310.py!}
    ```

### Virtual environment with `venv`

You can create an isolated virtual local environment in a directory using Python's `venv` module. Let's do this in the cloned repository (where the `requirements.txt` is):

<div class="termy">

```console
$ python -m venv env
```

Ein Projektgenerator verfügt immer über ein sehr spezifisches Setup, das Sie aktualisieren und an Ihre eigenen Bedürfnisse anpassen sollten, aber es könnte ein guter Ausgangspunkt für Ihr Projekt sein.

## Full Stack FastAPI PostgreSQL

### What is "Mounting"

"Mounting" means adding a complete "independent" application in a specific path, that then takes care of handling all the sub-paths.

This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

# Behind a Proxy

In some situations, you might need to use a **proxy** server like Traefik or Nginx with a configuration that adds an extra path prefix that is not seen by your application.

In these cases you can use `root_path` to configure your application.

The `root_path` is a mechanism provided by the ASGI specification (that FastAPI is built on, through Starlette).

The `root_path` is used to handle these specific cases.

```Python hl_lines="6"
{!../../../docs_src/first_steps/tutorial001.py!}
```

Das `@app.get("/")` sagt **FastAPI**, dass die Funktion direkt darunter für die Bearbeitung von Anfragen zuständig ist, die an:

 * den Pfad `/`
 * unter der Verwendung der <abbr title="eine HTTP GET Methode"><code>get</code>-Operation</abbr> gehen

!!! info "`@decorator` Information"

Um alle Optionen kennenzulernen, die Sie haben, schauen Sie sich <a href="https://docs.pydantic.dev/latest/concepts/types/" class="external-link" target="_blank">Pydantics Typübersicht</a> an. Sie werden im nächsten Kapitel ein paar Beispiele kennenlernen.

Da wir zum Beispiel im `Image`-Modell ein Feld `url` haben, können wir deklarieren, dass das eine Instanz von Pydantics `HttpUrl` sein soll, anstelle eines `str`:

    ├── schemas.py
    └── tests
        ├── __init__.py
        └── test_sql_app.py
```

## Create the new database session

First, we create a new database session with the new database.

We'll use an in-memory database that persists during the tests instead of the local file `sql_app.db`.

But the rest of the session code is more or less the same, we just copy it.

```Python hl_lines="8-13"

!!! tip