Spring 注解@Repository 和@Service
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Spring annotations @Repository and @Service
提问by BlueSky
What are the advantages of using @Repositoryand @Service?
使用@Repository和@Service 有什么好处？
Don't tell me about component scanning etc., I am looking forward to something extra benefits or features that are there if at all.
不要告诉我有关组件扫描等的信息，我很期待有一些额外的好处或功能，如果有的话。
what happens if I don't use it? what is that I would be missing?
如果我不使用它会怎样？我会错过什么？
回答by Donal Fellows
There are a few reasons:
有几个原因：
- It's easier to target pointcuts with more specific annotations. Do notunderestimate the usefulness of this!
- The
@Repositoryannotation carries with it some additional functionality: it causes exceptions to be wrapped up asDataAccessExceptions. - The
@Serviceannotation may gain additional semantics in the futurebut it's not happened yet…
- 使用更具体的注释更容易定位切入点。千万不能小看这个用处！
- 该
@Repository注释与它携带了一些附加功能：它会导致异常被包裹起来作为DataAccessException小号。 - 该
@Service注释可能获得额外的语义在未来，但它没有发生过......
回答by Luciano Fiandesio
The @Repositoryannotation (introduced in Spring 2.0) and @Serviceannotation (introduced in Spring 2.5) are specialization of the @Componentannotation.
的@Repository注释（在Spring 2.0引入）和@Service注释（在Spring 2.5引入）是专业化@Component注释。
The main advantage of using @Repositoryor @Serviceover @Componentis that it's easy to write an AOP pointcut that targets, for instance, all classes annotated with @Repository.
using @Repositoryor @Serviceover的主要优点@Component是很容易编写一个 AOP 切入点，例如，所有用@Repository.
Also, the specialized annotations help to clearly demarcate application layers (in a standard 3 tiers application).
此外，专门的注释有助于明确划分应用程序层（在标准的 3 层应用程序中）。
回答by nicholas.hauschild
I believe that there are two things Spring had in mind when they added these Component annotations.
我相信 Spring 在添加这些 Component 注解时考虑了两件事。
- They can be used to specify point cuts across all objects annotated with that sub-component. (All @Repository or all @Service pointcuts)
- I think Spring also mentioned that they would be adding some future functionality to them. (I have no citation for this, I just think I read this somewhere)
- 它们可用于在使用该子组件注释的所有对象上指定点切割。（所有@Repository 或所有@Service 切入点）
- 我认为 Spring 还提到他们将向他们添加一些未来的功能。（我没有引用这个，我只是想我在某处读过这个）
回答by lrkwz
If you TDDit would be useful to carefully design (an test of course) @Services because they will benefit of full injection of all the @Autowired components you have defined.
如果您使用TDD，仔细设计（当然是测试）@Services 会很有用，因为它们将受益于您定义的所有 @Autowired 组件的完全注入。
You could implement your functionalities directly into a @Controller for example, but in this case testing will be harder and you need to define all the mock elements (quite easier in springframework 3.1 but still "bad design").
例如，您可以将您的功能直接实现到 @Controller 中，但在这种情况下，测试将更加困难，您需要定义所有模拟元素（在 springframework 3.1 中相当容易，但仍然是“糟糕的设计”）。
