在Spring MVC应用程序的Controller层中使用@Transactional有什么好处

Question

In an Spring 4 MVC application, i noticed that the @Transactional annotation was used in Controller layer. But in many places it was recommended to use within the service layer (service implementation class).

What is the benefit of using @Transactional in @Controller class?

Also, i have a service layer implementation class, which updates the data to database, i noticed the usage of Transaction properties as below

@Transactional(propagation = Propagation.REQUIRED, readOnly = true)

readOnly = true, was to be used when the method uses find or fetch some data from database. But using readOnly = true, the service layer was able to save the data anyways. My application uses Spring 4 + Hibernate 4.2.20.

Transaction manager used by application

<bean id="transactionManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager" >
        <property name="sessionFactory" ref="sessionFactory" /> 
    </bean>

Using " readOnly = true " within the transaction will be able to save the data to database?

Answer 1

There is no reason to use the annotation @Transactional in the @Controller.

There is a simple reason not to do this: best practice. A @Controller should not be aware of data persistence in a MVC logic, only the Service layer.

Also Spring recommends not to annotate whole classes only certain methods, this is also a good practice so you can mantain easily your application.