如何在Litestar控制器中正确使用dependency-injector？

问题背景 #

使用Litestar开发项目原型时，希望通过dependency-injector框架实现控制器的依赖注入，但无法像FastAPI那样通过Depends直接集成，运行时出现类型不支持的错误。

项目结构 #

lite/
├── __init__.py
├── __main__.py
├── controllers.py
├── di.py
├── logging.py
├── main.py
├── services.py

现有代码片段 #

di.py #

from dependency_injector import containers, providers
from .services import Service

class Container(containers.DeclarativeContainer):
    service = providers.Factory(Service)

main.py #

import uvicorn
from .di import Container
from .logging import logger

if __name__ == "__main__":
    try:
        container = Container()
        container.wire(modules=[__name__, "lite", "lite.controllers"])

        config = uvicorn.Config(app="lite.main:app", port=3000)
        server = uvicorn.Server(config)
        server.run()
    except Exception as e:
        logger.exception(e)

main.py #

from litestar import Litestar
from .controllers import ExampleController
from litestar.logging import LoggingConfig

app = Litestar(
    route_handlers=[ExampleController],
    logging_config=LoggingConfig(
        root={"level": "INFO", "handlers": ["queue_listener"]},
        formatters={
            "standard": {
                "format": "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
            }
        },
        log_exceptions="always",
    ),
)

失败的控制器实现 #

from typing import Annotated
from litestar import Controller, get
from litestar.di import Provide as Depends
from litestar.params import Dependency
from .di import Container
from dependency_injector.wiring import Provide, inject
from .services import Service

class ExampleController(Controller):
    path = "/test"

    @get("/")
    @inject
    async def bar(self, service: Service = Depends(Provide[Container.service])) -> None:
        service.foo() # 仅打印"foo"

错误信息 #

Traceback (most recent call last):
  File "/workspaces/LiteTest/.venv/lib/python3.10/site-packages/litestar/_signature/model.py", line 101, in _deserializer
    return default_deserializer(target_type, value)
  File "/workspaces/LiteTest/.venv/lib/python3.10/site-packages/litestar/serialization/msgspec_hooks.py", line 139, in default_deserializer
    raise TypeError(f"Unsupported type: {type(value)!r}")
TypeError: Unsupported type: <class 'dependency_injector.wiring.Provide'>

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/workspaces/LiteTest/.venv/lib/python3.10/site-packages/litestar/_signature/model.py", line 203, in parse_values_from_connection_kwargs
    return convert(kwargs, cls, strict=False, dec_hook=deserializer, str_keys=True).to_dict()
msgspec.ValidationError: Unsupported type: <class 'dependency_injector.wiring.Provide'> - at `$.service`

已尝试的方案 #

• 直接在方法参数中使用Depends(Provide[...])注入
• 尝试重写控制器构造函数，但Controller基类不可修改
• 查阅Litestar和dependency-injector官方文档，无相关集成指导
• 找到一种不够优雅的变通方法：

from litestar import Controller, get
from litestar.di import Provide as Depends
from .di import Container, Provide, inject
from .services import Service

@inject
def _get_service(service: Service = Provide[Container.service]) -> Service:
    return service

def get_service() -> Service:
    return _get_service()

class ExampleController(Controller):
    path = "/test"

    @get("/", dependencies={"service": Depends(get_service)})
    async def bar(self, service: Service) -> None:
        service.foo()

问题根源是Litestar的参数解析系统无法识别dependency-injector的Provide类型，且同时混用了两套依赖注入机制导致冲突。以下是两种优雅的解决方式：

方案1：纯用dependency-injector的注入能力 #

去掉Litestar的Depends，仅使用dependency-injector的@inject和Provide，确保装饰器顺序正确（@inject靠近函数定义，让它先于Litestar路由装饰器执行）：

from litestar import Controller, get
from dependency_injector.wiring import inject, Provide
from .di import Container
from .services import Service

class ExampleController(Controller):
    path = "/test"

    @get("/")
    @inject
    async def bar(self, service: Service = Provide[Container.service]) -> None:
        service.foo()

注意：确保__main__.py中container.wire(modules=["lite.controllers"])已正确包含控制器模块，让dependency-injector能扫描到需要注入的参数。

方案2：对接Litestar的依赖注入系统 #

将dependency-injector容器注册为Litestar的应用级依赖，通过Litestar的依赖提供者获取服务实例：

1. 修改di.py，添加全局容器实例：

from dependency_injector import containers, providers
from .services import Service

class Container(containers.DeclarativeContainer):
    service = providers.Factory(Service)

# 创建全局容器实例
container = Container()

2. 修改main.py，初始化容器并注册为应用依赖：

from litestar import Litestar
from .controllers import ExampleController
from litestar.logging import LoggingConfig
from .di import container

# 初始化容器资源
container.init_resources()

app = Litestar(
    route_handlers=[ExampleController],
    logging_config=LoggingConfig(
        root={"level": "INFO", "handlers": ["queue_listener"]},
        formatters={
            "standard": {
                "format": "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
            }
        },
        log_exceptions="always",
    ),
    # 注册容器为应用级依赖
    dependencies={"container": container},
)

3. 修改控制器，通过Litestar依赖系统获取服务：

from litestar import Controller, get
from litestar.di import Provide
from .di import Container
from .services import Service

# 定义依赖提供者函数
def get_service(container: Container) -> Service:
    return container.service()

class ExampleController(Controller):
    path = "/test"

    @get("/", dependencies={"service": Provide(get_service)})
    async def bar(self, service: Service) -> None:
        service.foo()

内容的提问来源于stack exchange，提问作者Arthur Brenno Ribeiro Coelho