保持模块依赖规则下使用mediatr与dependency_injector注入报错求助

问题背景 #

模块依赖关系如下：

• application（依赖domain）
• domain（无依赖）
• persistence（依赖application）
• main.py（依赖所有模块）

使用mediatr和dependency_injector实现依赖注入时，触发错误：

AttributeError: 'Provide' object has no attribute 'get_person'

错误原因分析 #

1. 装饰器顺序错误：@inject装饰器放在@Mediator.handler之前，导致dependency_injector无法正确拦截Handler类的实例化，依赖未被注入，self.db仍是Provide对象而非实际的DBConnection实例。
2. 容器依赖未正确传递：主容器Container中，application_container和persistence_container独立创建，未建立依赖关联，导致ApplicationContainer的dbconnection依赖未被填充。
3. 接口与实现参数不匹配：IDBConnection定义的get_person参数id类型为str，但DBConnection实现中为int，会触发类型错误。
4. Wire范围不足：仅对__name__（main模块）进行wire，未覆盖application层模块，导致Handler类的注入逻辑未生效。

修复步骤 #

1. 调整装饰器顺序 #

将@inject移至@Mediator.handler之后，确保注入逻辑优先执行：

@Mediator.handler
@inject
class PersonQueryHandler:
    # ... 原有代码 ...

2. 修正主容器的依赖关联 #

在main.py的Container中，让application_container依赖persistence_container提供的database实例：

class Container(containers.DeclarativeContainer):
    mediator = providers.Singleton(Mediator)
    persistence_container = providers.Container(PersistenceContainer)
    application_container = providers.Container(
        ApplicationContainer,
        dbconnection=persistence_container.database
    )

3. 统一参数类型 #

修改persistence/storage.py中get_person的参数类型为str，与接口定义一致：

def get_person(self, id: str) -> Person:
    return Person(id=id, name="Razali", gender="Male")

4. 扩大Wire覆盖范围 #

在main函数启动时，将application层的模块加入wire范围：

container.wire(modules=[__name__, "application.personcontext.queries.person"])

完整修复代码 #

domain/models.py（无修改） #

from dataclasses import dataclass

@dataclass
class Person:
    id: str
    name: str
    gender: str

application/interfaces/database.py（无修改） #

from abc import ABC, abstractmethod
from domain.models import Person

class IDBConnection(ABC):
    @abstractmethod
    def get_person(self, id: str) -> Person:
        pass

application/containers.py（无修改） #

from dependency_injector import containers, providers
class ApplicationContainer(containers.DeclarativeContainer):
    dbconnection = providers.Dependency()

application/personcontext/queries/person.py（修改装饰器顺序） #

from domain.models import Person
from mediatr import Mediator
from application.interfaces.database import IDBConnection
from dependency_injector.wiring import inject, Provide
from application.containers import ApplicationContainer

class PersonQuery:
    def __init__(self, id: str) -> None:
        self.id = id

@Mediator.handler
@inject
class PersonQueryHandler:
    def __init__(self, db: IDBConnection = Provide[ApplicationContainer.dbconnection]) -> None:
        self.db: IDBConnection = db

    def handle(self, request: PersonQuery):
        return self.db.get_person(request.id)

persistence/containers.py（无修改） #

from dependency_injector import containers, providers
from application.interfaces.database import IDBConnection
from persistence.storage import DBConnection
from application.containers import ApplicationContainer

class PersistenceContainer(containers.DeclarativeContainer):
    database = providers.Singleton(IDBConnection, DBConnection())
    application_container = providers.Container(
        ApplicationContainer,
        dbconnection=database
    )

persistence/storage.py（修改参数类型） #

from application.interfaces.database import IDBConnection
from domain.models import Person

class DBConnection(IDBConnection):
    def get_person(self, id: str) -> Person:
        return Person(id=id, name="Razali", gender="Male")

main.py（修改容器关联与wire范围） #

from mediatr import Mediator
from application.personcontext.queries.person import PersonQuery
from dependency_injector import containers, providers
from dependency_injector.wiring import inject, Provide
from persistence.containers import PersistenceContainer
from application.containers import ApplicationContainer

class Container(containers.DeclarativeContainer):
    mediator = providers.Singleton(Mediator)
    persistence_container = providers.Container(PersistenceContainer)
    application_container = providers.Container(
        ApplicationContainer,
        dbconnection=persistence_container.database
    )

@inject
def main(mediator: Mediator = Provide[Container.mediator]):
    response = mediator.send(PersonQuery("1"))
    print(response)

if __name__ == '__main__':
    container = Container()
    container.init_resources()
    # Wire main模块和application的handler模块
    container.wire(modules=[__name__, "application.personcontext.queries.person"])
    main()

验证结果 #

运行main.py后，将输出：

Person(id='1', name='Razali', gender='Male')

内容的提问来源于stack exchange，提问作者RStyle