Thanks to <a href="https://www.starlette.io/testclient/" class="external-link" target="_blank">Starlette</a>, testing **FastAPI** applications is easy and enjoyable.

It is based on <a href="https://www.python-httpx.org" class="external-link" target="_blank">HTTPX</a>, which in turn is designed based on Requests, so it's very familiar and intuitive.

# Generate Clients

As **FastAPI** is based on the OpenAPI specification, you get automatic compatibility with many tools, including the automatic API docs (provided by Swagger UI).

One particular advantage that is not necessarily obvious is that you can **generate clients** (sometimes called <abbr title="Software Development Kits">**SDKs**</abbr> ) for your API, for many different **programming languages**.

## OpenAPI Client Generators

## Read the Tutorial first

The next sections assume you already read the main [Tutorial - User Guide: Security](../../tutorial/security/index.md){.internal-link target=_blank}.

        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect username or password",
            headers={"WWW-Authenticate": "Basic"},
        )
    return credentials.username


@app.get("/users/me")
def read_current_user(username: Annotated[str, Depends(get_current_username)]):

    assert response.json() == {"detail": "Not authenticated"}


def test_security_http_bearer_incorrect_scheme_credentials():
    response = client.get("/users/me", headers={"Authorization": "Basic notreally"})
    assert response.status_code == 403, response.text
    assert response.json() == {"detail": "Invalid authentication credentials"}


def test_openapi_schema():
    response = client.get("/openapi.json")

    * But it provides you the tools to build simple web applications, with routing based on paths, etc.
    * If you are comparing Starlette, compare it against Sanic, Flask, Django, etc. Web frameworks (or microframeworks).
* **FastAPI**:

# Devolver una respuesta directamente

Cuando creas una *operación de path* normalmente puedes devolver cualquier dato: un `dict`, una `list`, un modelo Pydantic, un modelo de base de datos, etc.

Por defecto, **FastAPI** convertiría automáticamente ese valor devuelto a JSON usando el `jsonable_encoder` explicado en [Codificador Compatible JSON](../tutorial/encoder.md){.internal-link target=_blank}.

And then you also read how to handle [CORS with the `CORSMiddleware`](../tutorial/cors.md){.internal-link target=_blank}.

In this section we'll see how to use other middlewares.

## Adding ASGI middlewares

As **FastAPI** is based on Starlette and implements the <abbr title="Asynchronous Server Gateway Interface">ASGI</abbr> specification, you can use any ASGI middleware.

e potente.
* Sicurezza e autenticazione, incluso il supporto per **OAuth2** con **token JWT** e autenticazione **HTTP Basic**.
* Tecniche più avanzate (ma ugualmente semplici) per dichiarare **modelli JSON altamente nidificati** (grazie a Pydantic).
* E altre funzionalità (grazie a Starlette) come:
    * **WebSockets**
    * **GraphQL**

{!../../../docs_src/sql_databases/sql_app/database.py!}
```

### 创建一个`Base`类

现在我们将使用`declarative_base()`返回一个类。

稍后我们将用这个类继承，来创建每个数据库模型或类（ORM 模型）：

```Python hl_lines="13"
{!../../../docs_src/sql_databases/sql_app/database.py!}
```

## 创建数据库模型

现在让我们看看文件`sql_app/models.py`。

### 用`Base`类来创建 SQLAlchemy 模型

我们将使用我们之前创建的`Base`类来创建 SQLAlchemy 模型。

!!! tip