为什么将@Transactional 与@Service 一起使用而不是与@Controller 一起使用 [英] Why use @Transactional with @Service instead of with @Controller
问题描述
我在 stack-overflow 文章中看到了很多评论，我发现了一些关于 @Transactional 与 @Service 或 @Controller 一起使用的事情
I have seen many comments in stack-overflow articles I found certain things about either @Transactional use with @Service or with @Controller
通常，应该将事务放在服务层."
"Usually, one should put a transaction at the service layer."
正常情况是在服务层级别进行注释"
"The normal case would be to annotate on a service layer level"
"认为事务属于服务层.它是了解工作单元和用例的人.如果您将多个 DAO 注入到需要在单个事务中协同工作的服务中，这是正确的答案."[来源]
"Think transactions belong on the Service layer. It's the one that knows about units of work and use cases. It's the right answer if you have several DAOs injected into a Service that need to work together in a single transaction." [Source]
将@transactional 与@service 层一起使用的缺点
如果我有 2 个方法，例如 saveUser() 和 saveEmail()(因为我将电子邮件存储在数据库中以便稍后发送 - 就像一个队列)我会在我的服务中创建一个方法 saveUserAndSendEmail(User user)是交易性的.[来源]
If I had 2 methods for example saveUser() and saveEmail() (because I store the emails in a database to send them later - like a queue) I would create in my service a method saveUserAndSendEmail(User user) which would be transactional. [Source]
这意味着我在服务层创建了许多方法而不是一个保存通用方法，如下所示
public <T> long save(T entity) throws DataAccessException {
Session session = sessionFactory.getCurrentSession();
long getGenVal=(Long) session.save(entity);
return getGenVal;
}
根据上面的解决方案，这意味着我们有很多方法，比如像LOL..
public
public
public
克服这种情况
我在@Controller 中使用@Transactional 并创建一个通用保存方法并使用这个简单的保存方法保存所有实体/模型.如果任何方法保存失败，则控制器回滚所有事务成功.
I USE THE @Transactional in @Controller and Just make a Generic Save Method and save all the entities/ model using this simple save method. and if any method fail to save then all the transactions in controller rollback successfully.
确保@Transactional 应该与@Controller 一起使用的其他情况
在@Controller 中:
In @Controller:
pt.save(entity1);
pt.save(entity2);
int a = 2/0;
pt.save(entity3);
如果@Transactional on Service，前2个实体成功保存，但第三个不是，它不会回滚所有事务
万一，@Controller 上的@Transactional 发生异常时所有事务回滚
为什么堆栈溢出会问，不要在控制器中进行交易.将它们放在您的服务层类中."?[来源]
why stack-overflow asked , "Don't do transactions in your controller. Put them in your service layer classes."? [source]
推荐答案
你问的是最佳实践，最佳实践是在服务层标记 @Transactional 因为一个 @Controller 不应该意识到 MVC 逻辑中的数据持久性.@Service 基于分析生成的用例构建，了解工作单元，也实现了重用方面的思考:如果您从 Web 上下文切换到桌面上下文(例如，或一些其他的视觉前端)，其中 @Controller 层不存在你没有问题，因为所有都封装在服务层中.@Service 是一个契约，表示层的修改不需要重写 @Service 代码.
但是 Spring 并不关心你把你的事务边界放在哪里，你可以放 @Controller 但你的应用程序可能会更难维护.
You are asking about best practice, and best practice is to mark @Transactional in the service layer because a @Controller should not be aware of data persistence in a MVC logic.
@Service is constructed on use-case generated from analysis and knows about unit of works and is also realized thinking in terms of reuse: if you switch from a web context to a desktop one (for example, or some other visual frontend) where @Controller layer doesn't exist you don't have problems because all is encapsulated in service layer.
A @Service is a contract and a modification in presentation layer should not require a rewrite of @Service code.
But Spring don't care about where you put your your transaction boundaries, you can put on @Controller but your application may will be harder to be maintained.
我希望这已经足够清楚了.对不起，如果没有；英语不是我的母语.
I hope this is clear enough. Sorry if not; English is not my native language.
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