Convert any object to something that can be encoded in JSON.

    This is used internally by FastAPI to make sure anything you return can be
    encoded as JSON before it is sent to the client.

    You can also use it yourself, for example to convert objects before saving them
    in a database that supports only JSON.

    Read more about it in the

```Python hl_lines="2  7"
{!../../../docs_src/custom_response/tutorial001b.py!}
```

!!! info

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

=== "Python 3.10+"

    ```Python hl_lines="1  14-15  18-20  33"
    {!> ../../../docs_src/extra_models/tutorial003_py310.py!}
    ```

=== "Python 3.8+"

    Make sure you [Upgrade the FastAPI version](../deployment/versions.md#upgrading-the-fastapi-versions){.internal-link target=_blank} to at least 0.95.1 before using `Annotated`.

## Declare metadata

You can declare all the same parameters as for `Query`.

For example, to declare a `title` metadata value for the path parameter `item_id` you can type:

=== "Python 3.10+"

## Use `SecurityScopes`

Now update the dependency `get_current_user`.

This is the one used by the dependencies above.

Here's were we are using the same OAuth2 scheme we created before, declaring it as a dependency: `oauth2_scheme`.

For example, let's say that you want to have a *path operation* that allows to update items, and returns HTTP status codes of 200 "OK" when successful.

But you also want it to accept new items. And when the items didn't exist before, it creates them, and returns an HTTP status code of 201 "Created".

To achieve that, import `JSONResponse`, and return your content there directly, setting the `status_code` that you want:

=== "Python 3.10+"

```Python
if "stanleyjobsox" == "stanleyjobson" and "love123" == "swordfish":
    ...
```

Python will have to compare the whole `stanleyjobso` in both `stanleyjobsox` and `stanleyjobson` before realizing that both strings are not the same. So it will take some extra microseconds to reply back "Incorrect username or password".

#### The time to answer helps the attackers

Das wollen wir besser machen: Laden wir das Modell, bevor die Requests bearbeitet werden, aber unmittelbar bevor die Anwendung beginnt, Requests zu empfangen, und nicht, während der Code geladen wird.

## Lifespan

### Multiple File Uploads with Additional Metadata

And the same way as before, you can use `File()` to set additional parameters, even for `UploadFile`:

=== "Python 3.9+"

    ```Python hl_lines="11  18-20"
    {!> ../../../docs_src/request_files/tutorial003_an_py39.py!}
    ```