## Password hashing

"Hashing" means converting some content (a password in this case) into a sequence of bytes (just a string) that looks like gibberish.

Whenever you pass exactly the same content (exactly the same password) you get exactly the same gibberish.

* `main`: il file `main.py` (il "modulo" Python).
* `app`: l'oggetto creato dentro `main.py` con la riga di codice `app = FastAPI()`.
* `--reload`: ricarica il server se vengono rilevati cambiamenti del codice. Usalo solo durante la fase di sviluppo.

</details>

### Testa l'API

Apri il browser all'indirizzo <a href="http://127.0.0.1:8000/items/5?q=somequery" class="external-link" target="_blank">http://127.0.0.1:8000/items/5?q=somequery</a>.

{!../../../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

from fastapi.exceptions import HTTPException
from fastapi.openapi.models import OAuth2 as OAuth2Model
from fastapi.openapi.models import OAuthFlows as OAuthFlowsModel
from fastapi.param_functions import Form
from fastapi.security.base import SecurityBase
from fastapi.security.utils import get_authorization_scheme_param
from starlette.requests import Request
from starlette.status import HTTP_401_UNAUTHORIZED, HTTP_403_FORBIDDEN

* 100% <abbr title=" Lượng code đã được kiểm thử tự động">test coverage</abbr>.
* 100% <abbr title="Python type annotations, với điều này trình soạn thảo của bạn và các công cụ bên ngoài có thể hỗ trợ bạn tốt hơn">type annotated</abbr> code base.
* Được sử dụng cho các ứng dụng sản phẩm.

## Tính năng của Starlette

## What is "Dependency Injection"

**"Dependency Injection"** means, in programming, that there is a way for your code (in this case, your *path operation functions*) to declare things that it requires to work and use: "dependencies".

And then, that system (in this case **FastAPI**) will take care of doing whatever is needed to provide your code with those needed dependencies ("inject" the dependencies).

                ],
            ),
        ):
            return item

    # TODO: enable these tests once/if Form(embed=False) is supported
    # TODO: In that case, define if File() should support example/examples too
    # @app.post("/form_example")
    # def form_example(firstname: str = Form(example="John")):
    #     return firstname

    # @app.post("/form_examples")

* <a href="https://github.com/tiangolo/full-stack-flask-couchdb" class="external-link" target="_blank">https://github.com/tiangolo/full-stack-flask-couchdb</a>

And these same full-stack generators were the base of the [**FastAPI** Project Generators](project-generation.md){.internal-link target=_blank}.

!!! info
    Flask-apispec was created by the same Marshmallow developers.

!!! check "Inspired **FastAPI** to"

The contents that you return from your *path operation function* will be put inside of that `Response`.

And if that `Response` has a JSON media type (`application/json`), like is the case with the `JSONResponse` and `UJSONResponse`, the data you return will be automatically converted (and filtered) with any Pydantic `response_model` that you declared in the *path operation decorator*.

!!! note

    Any HTTP (error) status code 401 "UNAUTHORIZED" is supposed to also return a `WWW-Authenticate` header.

    In the case of bearer tokens (our case), the value of that header should be `Bearer`.

    You can actually skip that extra header and it would still work.

    But it's provided here to be compliant with the specifications.