DAO 和 Repository 模式有什么区别? [英] What is the difference between DAO and Repository patterns?

问题描述

数据访问对象 (DAO) 和存储库模式之间有什么区别?我正在使用 Enterprise Java Beans (EJB3)、Hibernate ORM 作为基础设施、域驱动设计 (DDD) 和测试驱动开发 (TDD) 作为设计技术来开发应用程序.

What is the difference between Data Access Objects (DAO) and Repository patterns? I am developing an application using Enterprise Java Beans (EJB3), Hibernate ORM as infrastructure, and Domain-Driven Design (DDD) and Test-Driven Development (TDD) as design techniques.

推荐答案

DAO 是数据持久化的抽象.
Repository 是对象集合的抽象.

DAO is an abstraction of data persistence.
Repository is an abstraction of a collection of objects.

DAO 会被认为更接近数据库，通常以表为中心.
Repository 会被认为更接近于域，只处理聚合根.

DAO would be considered closer to the database, often table-centric.
Repository would be considered closer to the Domain, dealing only in Aggregate Roots.

Repository 可以使用 DAO 来实现，但你不会反其道而行之.

Repository could be implemented using DAO's, but you wouldn't do the opposite.

此外，Repository 通常是一个较窄的接口.它应该是一个简单的对象集合，带有 Get(id)、Find(ISpecification)、Add(Entity).

Also, a Repository is generally a narrower interface. It should be simply a collection of objects, with a Get(id), Find(ISpecification), Add(Entity).

Update 之类的方法适用于 DAO，但不适用于 Repository - 当使用 Repository 时，对实体的更改通常由单独的 UnitOfWork 跟踪.

A method like Update is appropriate on a DAO, but not a Repository - when using a Repository, changes to entities would usually be tracked by separate UnitOfWork.

看到称为 Repository 的实现似乎很常见，它实际上更像是一个 DAO，因此我认为它们之间的区别存在一些混淆.

It does seem common to see implementations called a Repository that is really more of a DAO, and hence I think there is some confusion about the difference between them.

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