我应该将@Transactional 注释放在哪里:在接口定义或实现类中?

2022-01-13 00:00:00 annotations coding-style spring java

代码中标题的问题:

@Transactional (readonly = true)
public interface FooService {
   void doSmth ();
}


public class FooServiceImpl implements FooService {
   ...
}

对

public interface FooService {
   void doSmth ();
}

@Transactional (readonly = true)
public class FooServiceImpl implements FooService {
   ...
}

推荐答案

来自 http://static.springsource.org/spring/docs/2.0.x/reference/transaction.html

Spring 团队的建议是您只使用 @Transactional 注释来注释具体类，而不是注释接口.您当然可以将 @Transactional接口(或接口方法)上的 注释，但这只会在您使用基于接口的代理时按预期工作.注释不被继承这一事实意味着，如果您使用基于类的代理，则基于类的代理基础设施将无法识别事务设置，并且对象不会被包装在事务代理中(这绝对是糟糕).所以请务必听取 Spring 团队的建议，只使用 @Transactional 注释来注释具体类(以及具体类的方法).

The Spring team's recommendation is that you only annotate concrete classes with the @Transactional annotation, as opposed to annotating interfaces. You certainly can place the @Transactional annotation on an interface (or an interface method), but this will only work as you would expect it to if you are using interface-based proxies. The fact that annotations are not inherited means that if you are using class-based proxies then the transaction settings will not be recognised by the class-based proxying infrastructure and the object will not be wrapped in a transactional proxy (which would be decidedly bad). So please do take the Spring team's advice and only annotate concrete classes (and the methods of concrete classes) with the @Transactional annotation.

注意:由于这种机制是基于代理的，只有通过代理传入的外部"方法调用才会被拦截.这意味着自调用"，即目标内的方法对象调用目标对象的某些其他方法，即使调用的方法标有 @Transactional!

Note: Since this mechanism is based on proxies, only 'external' method calls coming in through the proxy will be intercepted. This means that 'self-invocation', i.e. a method within the target object calling some other method of the target object, won't lead to an actual transaction at runtime even if the invoked method is marked with @Transactional!

(在第一句中添加了重点，原文中的其他重点.)

(Emphasis added to the first sentence, other emphasis from the original.)

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