Esse sistema foi pensado para ser fácil de usar, e permitir que qualquer desenvolvedor possa integrar facilmente outros componentes ao **FastAPI**.

## O que é "Injeção de Dependência" { #what-is-dependency-injection }

* How to set **validation constraints** as `maximum_length` or `regex`.
* A very powerful and easy to use **<dfn title="also known as components, resources, providers, services, injectables">Dependency Injection</dfn>** system.
* Security and authentication, including support for **OAuth2** with **JWT tokens** and **HTTP Basic** auth.

* Alle Schlüsselwort-Argumente, die an die Taskfunktion übergeben werden sollen (`message="some notification"`).

## Dependency Injection { #dependency-injection }

{* ../../docs_src/security/tutorial002_an_py310.py hl[5,12:6] *}

## Crear una dependencia `get_current_user` { #create-a-get-current-user-dependency }

Vamos a crear una dependencia `get_current_user`.

¿Recuerdas que las dependencias pueden tener sub-dependencias?

`get_current_user` tendrá una dependencia con el mismo `oauth2_scheme` que creamos antes.

### 建立資料表 { #create-the-tables }

接著我們新增一個函式，使用 `SQLModel.metadata.create_all(engine)` 為所有「資料表模型」建立資料表。

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[21:22] hl[21:22] *}

### 建立 Session 依賴 { #create-a-session-dependency }

「`Session`」會在記憶體中保存物件並追蹤資料需要的任何變更，然後透過「`engine`」與資料庫溝通。

我們會用 `yield` 建立一個 FastAPI 的「依賴」，為每個請求提供一個新的 `Session`。這可確保每個請求只使用單一的 session。🤓

接著我們建立一個 `Annotated` 的依賴 `SessionDep`，讓後續使用這個依賴的程式碼更簡潔。

 *   <li>Streams include primitive-specialized variants such as {@code IntStream}, the use of which
 *       is strongly recommended.
 *   <li>Streams are standard Java, not requiring a third-party dependency (but requiring <a
 *       href="https://developer.android.com/studio/write/java8-support#library-desugaring">library
 *       desugaring</a> or <a

 *   <li>Streams include primitive-specialized variants such as {@code IntStream}, the use of which
 *       is strongly recommended.
 *   <li>Streams are standard Java, not requiring a third-party dependency.
 * </ul>
 *
 * <h3>Example</h3>
 *
 * <p>Here is an example that accepts a list from a database call, filters it based on a predicate,

```Python
oauth2_scheme(some, parameters)
```

Dolayısıyla `Depends` ile kullanılabilir.

### Kullanın { #use-it }

Artık `Depends` ile bir dependency olarak `oauth2_scheme`’i geçebilirsiniz.

{* ../../docs_src/security/tutorial001_an_py310.py hl[12] *}

Bu dependency, *path operation function* içindeki `token` parametresine atanacak bir `str` sağlar.

### Dependencies { #dependencies }

The same applies for [dependencies](tutorial/dependencies/index.md). If a dependency is a standard `def` function instead of `async def`, it is run in the external threadpool.

### Sub-dependencies { #sub-dependencies }

然后，我们来添加一个函数，使用 `SQLModel.metadata.create_all(engine)` 为所有*表模型***创建表**。

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[21:22] hl[21:22] *}

### 创建会话（Session）依赖项 { #create-a-session-dependency }

**`Session`** 会存储**内存中的对象**并跟踪数据中所需更改的内容，然后它**使用 `engine`** 与数据库进行通信。

我们会使用 `yield` 创建一个 FastAPI **依赖项**，为每个请求提供一个新的 `Session`。这确保我们每个请求使用一个单独的会话。🤓

然后我们创建一个 `Annotated` 的依赖项 `SessionDep` 来简化其他也会用到此依赖的代码。