Spring transaction behavior in private & internal methods

This post is to detail on the spring behavior when @Transactional annotations are applied on private methods or when transactional methods are called from within a method in the same class.

Transactional Private Methods

public class Bean {
  public void doStuff() {
     doPrivateStuff();
  }
  @Transactional
  private void doPrivateStuff() {

  }
}

...

Bean bean = (Bean)appContext.getBean("bean");
bean.doStuff();

@Transactional will have no effect if used to annotate private methods. The proxy generator will ignore them.
As per the Spring manual

Method visibility and @Transactional
When using proxies, you should apply the @Transactional annotation only to methods with public visibility. If you do annotate protected, private or package-visible methods with the @Transactional annotation, no error is raised, but the annotated method does not exhibit the configured transactional settings. Consider the use of AspectJ if you need to annotate non-public methods.

Calling internal transactional methods

public class Bean {
   public void doStuff() {
     doTransactionStuff();
   }

   @Transactional
   public void doTransactionStuff() {

   }
}

This will open a transaction:

Bean bean = (Bean)appContext.getBean("bean");
bean.doTransactionStuff();

This will not:

Bean bean = (Bean)appContext.getBean("bean");
bean.doStuff();

As per the Spring manual
Note: In proxy mode (which is the default), 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!

Consider the use of AspectJ mode if you expect self-invocations to be wrapped with transactions as well. In this case, there won’t be a proxy in the first place; instead, the target class will be ‘weaved’ (i.e. its byte code will be modified) in order to turn @Transactional into runtime behavior on any kind of method.

Summary

The @Transactional annotation defines a transaction boundary, and Spring will start/rollback/commit the transaction every time a @Transactional-annotated method is entered or exited.
If you execute a @Transactional-annotated method, and that method then calls another method in another class, and that one calls another one, which eventually does some database work, then you’re still inside the transaction.

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