获取当前用户

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English version

上一章中，（基于依赖注入系统的）安全系统向路径操作函数传递了 str 类型的 token：

Python 3.9+

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


@app.get("/items/")
async def read_items(token: Annotated[str, Depends(oauth2_scheme)]):
    return {"token": token}

🤓 Other versions and variants

Python 3.10+Python 3.10+ - non-AnnotatedPython 3.9+ - non-Annotated

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


@app.get("/items/")
async def read_items(token: Annotated[str, Depends(oauth2_scheme)]):
    return {"token": token}

Tip

Prefer to use the Annotated version if possible.

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


@app.get("/items/")
async def read_items(token: str = Depends(oauth2_scheme)):
    return {"token": token}

Tip

Prefer to use the Annotated version if possible.

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


@app.get("/items/")
async def read_items(token: str = Depends(oauth2_scheme)):
    return {"token": token}

但这并不实用。

接下来，我们学习如何返回当前用户。

创建用户模型

首先，创建 Pydantic 用户模型。

与使用 Pydantic 声明请求体相同，并且可在任何位置使用：

Python 3.10+

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: Annotated[str, Depends(oauth2_scheme)]):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: Annotated[User, Depends(get_current_user)]):
    return current_user

🤓 Other versions and variants

Python 3.10+ - non-Annotated

Tip

Prefer to use the Annotated version if possible.

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: str = Depends(oauth2_scheme)):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: User = Depends(get_current_user)):
    return current_user

创建 get_current_user 依赖项

创建 get_current_user 依赖项。

还记得依赖项支持子依赖项吗？

get_current_user 使用 oauth2_scheme 作为依赖项。

与之前直接在路径操作中的做法相同，新的 get_current_user 依赖项从子依赖项 oauth2_scheme 中接收 str 类型的 token：

Python 3.10+

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: Annotated[str, Depends(oauth2_scheme)]):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: Annotated[User, Depends(get_current_user)]):
    return current_user

🤓 Other versions and variants

Python 3.10+ - non-Annotated

Tip

Prefer to use the Annotated version if possible.

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: str = Depends(oauth2_scheme)):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: User = Depends(get_current_user)):
    return current_user

获取用户

get_current_user 使用创建的（伪）工具函数，该函数接收 str 类型的令牌，并返回 Pydantic 的 User 模型：

Python 3.10+

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: Annotated[str, Depends(oauth2_scheme)]):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: Annotated[User, Depends(get_current_user)]):
    return current_user

🤓 Other versions and variants

Python 3.10+ - non-Annotated

Tip

Prefer to use the Annotated version if possible.

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: str = Depends(oauth2_scheme)):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: User = Depends(get_current_user)):
    return current_user

注入当前用户

在路径操作 的 Depends 中使用 get_current_user：

Python 3.10+

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: Annotated[str, Depends(oauth2_scheme)]):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: Annotated[User, Depends(get_current_user)]):
    return current_user

🤓 Other versions and variants

Python 3.10+ - non-Annotated

Tip

Prefer to use the Annotated version if possible.

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: str = Depends(oauth2_scheme)):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: User = Depends(get_current_user)):
    return current_user

注意，此处把 current_user 的类型声明为 Pydantic 的 User 模型。

这有助于在函数内部使用代码补全和类型检查。

提示

还记得请求体也是使用 Pydantic 模型声明的吧。

放心，因为使用了 Depends，FastAPI 不会搞混。

检查

依赖系统的这种设计方式可以支持不同的依赖项返回同一个 User 模型。

而不是局限于只能有一个返回该类型数据的依赖项。

其它模型

接下来，直接在路径操作函数中获取当前用户，并用 Depends 在依赖注入系统中处理安全机制。

开发者可以使用任何模型或数据满足安全需求（本例中是 Pydantic 的 User 模型）。

而且，不局限于只能使用特定的数据模型、类或类型。

不想在模型中使用 username，而是使用 id 和 email？当然可以。这些工具也支持。

只想使用字符串？或字典？甚至是数据库类模型的实例？工作方式都一样。

实际上，就算登录应用的不是用户，而是只拥有访问令牌的机器人、程序或其它系统？工作方式也一样。

尽管使用应用所需的任何模型、类、数据库。FastAPI 通过依赖注入系统都能帮您搞定。

代码大小

这个示例看起来有些冗长。毕竟这个文件同时包含了安全、数据模型的工具函数，以及路径操作等代码。

但，关键是：

安全和依赖注入的代码只需要写一次。

就算写得再复杂，也只是在一个位置写一次就够了。所以，要多复杂就可以写多复杂。

但是，就算有数千个端点（路径操作），它们都可以使用同一个安全系统。

而且，所有端点（或它们的任何部件）都可以利用这些依赖项或任何其它依赖项。

所有路径操作只需 3 行代码就可以了：

Python 3.10+

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: Annotated[str, Depends(oauth2_scheme)]):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: Annotated[User, Depends(get_current_user)]):
    return current_user

🤓 Other versions and variants

Python 3.10+ - non-Annotated

Tip

Prefer to use the Annotated version if possible.

from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer
from pydantic import BaseModel

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")


class User(BaseModel):
    username: str
    email: str | None = None
    full_name: str | None = None
    disabled: bool | None = None


def fake_decode_token(token):
    return User(
        username=token + "fakedecoded", email="john@example.com", full_name="John Doe"
    )


async def get_current_user(token: str = Depends(oauth2_scheme)):
    user = fake_decode_token(token)
    return user


@app.get("/users/me")
async def read_users_me(current_user: User = Depends(get_current_user)):
    return current_user

小结

现在，我们可以直接在路径操作函数中获取当前用户。

至此，安全的内容已经讲了一半。

只要再为用户或客户端的路径操作添加真正发送 username 和 password 的功能就可以了。

下一章见。