For web MVC Spring app should @Transactional go on controller or service?

Question

For WebApplicationContext, should I put @Transactional annotations in the controller or in services? The Spring docs have me a bit confused.

Here is my

Answer 1

The Service is the best place for putting transactional demarcations. The service should hold the detail-level use case behavior for a user interaction, meaning stuff that would logically go together in a transaction. Also that way a separation is maintained between web application glue code and business logic.

There are a lot of CRUD applications that don't have any significant business logic, for them having a service layer that just passes stuff through between the controllers and data access objects is not useful. In those cases you could get away with putting the transaction annotation on the data access objects.

Putting the transactional annotation on the controller can cause problems, see [the Spring MVC documentation][1], 17.3.2:

A common pitfall when working with annotated controller classes happens when applying functionality that requires creating a proxy for the controller object (e.g. @Transactional methods). Usually you will introduce an interface for the controller in order to use JDK dynamic proxies. To make this work you must move the @RequestMapping annotations, as well as any other type and method-level annotations (e.g. @ModelAttribute, @InitBinder) to the interface as well as the mapping mechanism can only "see" the interface exposed by the proxy. Alternatively, you could activate proxy-target-class="true" in the configuration for the functionality applied to the controller (in our transaction scenario in ). Doing so indicates that CGLIB-based subclass proxies should be used instead of interface-based JDK proxies. For more information on various proxying mechanisms see Section 9.6, “Proxying mechanisms”.

The transaction propagation behaviors that you set up on the attributes decide what happens when a transactional method calls another transactional method. You can configure it so that the method called uses the same transaction, or so that it always uses a new transaction.

By having multiple calls to your service in the example code you're defeating the transactional purpose of the service. The different calls to your service will execute in different transactions if you put the transactional annotations on the service.