It is also commonly used for other applications that don't necessarily need a database, user management, or any of the many features that come pre-built in Django. Although many of these features can be added with plug-ins.

This decoupling of parts, and being a "microframework" that could be extended to cover exactly what is needed was a key feature that I wanted to keep.

In particular, this may be a good alternative to logic in a middleware.

For example, if you want to read or manipulate the request body before it is processed by your application.

!!! danger
    This is an "advanced" feature.

    If you are just starting with **FastAPI** you might want to skip this section.

## Use cases

Some use cases include:

* Ask a **question** or ask about a **problem**.
* Suggest a new **feature**.

**Note**: if you do it, then I'm going to ask you to also help others. 😉

## Review Pull Requests

You can help me review pull requests from others.

Again, please try your best to be kind. 🤗

!!! check
    The `prefix`, `tags`, `responses`, and `dependencies` parameters are (as in many other cases) just a feature from **FastAPI** to help you avoid code duplication.

### Import the dependencies

This code lives in the module `app.routers.items`, the file `app/routers/items.py`.

## Type Hints with Metadata Annotations

Python also has a feature that allows putting **additional metadata** in these type hints using `Annotated`.

=== "Python 3.9+"

    In Python 3.9, `Annotated` is part of the standard library, so you can import it from `typing`.

Trong lần khảo sát cuối cùng dành cho các lập trình viên Python, đã rõ ràng <a href="https://www.jetbrains.com/research/python-developers-survey-2017/#tools-and-features" class="external-link" target="_blank">rằng đa số các lập trình viên sử dụng tính năng "autocompletion"</a>.

But for `Item-Output`, `description` is **required**, it has a red asterisk.

<div class="screenshot">
<img src="/img/tutorial/separate-openapi-schemas/image04.png">
</div>

With this feature from **Pydantic v2**, your API documentation is more **precise**, and if you have autogenerated clients and SDKs, they will be more precise too, with a better **developer experience** and consistency. 🎉

## Do not Separate Schemas

    Einige könnten noch nicht alle zusätzlichen Informationen anzeigen, die Sie deklariert haben, obwohl in den meisten Fällen geplant ist, das fehlende Feature zu implementieren.

Sie können einen Titel hinzufügen – `title`:

=== "Python 3.10+"

    ```Python hl_lines="10"
    {!> ../../../docs_src/query_params_str_validations/tutorial007_an_py310.py!}
    ```

The hierarchy is like:

* **Uvicorn**: an ASGI server
    * **Starlette**: (uses Uvicorn) a web microframework
        * **FastAPI**: (uses Starlette) an API microframework with several additional features for building APIs, with data validation, etc.

* **Uvicorn**:

# Advanced Security

## Additional Features

There are some extra features to handle security apart from the ones covered in the [Tutorial - User Guide: Security](../../tutorial/security/index.md){.internal-link target=_blank}.

!!! tip
    The next sections are **not necessarily "advanced"**.

    And it's possible that for your use case, the solution is in one of them.

## Read the Tutorial first