Where can I use #Transactional - spring

Question

Can someone explain me why this will work:
#Transactional
#Test
public void test() {
save();
}
public void save() {
Scenario scenar = new Scenario();
sessionFactory.getCurrentSession().save(scenar);
}
And this won't, because it won't find a transaction:
#Test
public void test() {
save();
}
#Transactional
public void save() {
Scenario scenar = new Scenario();
sessionFactory.getCurrentSession().save(scenar);
}
Thank you!

Answer 1

Spring #Transactional annotation works using Spring AOP. This means, that when a bean that contains a method with that annotation is injected as a dependency for a different bean, it gets wrapped in a proxy. This proxy has the same interface as the bean, but performs additional actions before a method is invoked (wrapping it in a transaction in this case). You can think of it as a sort of a decorator. You can even see the proxy being invoked when you debug your application.
Now, when the method that you annotate with #Transactional is called from the same class, there is no (at least, no easy) way to inject the proxy. There just isn't a way to replace the object referenced by the "this" keyword in Java.
More reading on Spring AOP proxies.

Answer 2

As you have a method annotated as #Test I assume this is part of a Junit Test class.
Spring developpers know that test methods usually do not implement interfaces, and as such cannot support JDK proxying. So they specially support #Transactional annotation on a #Test method. The doc says :
Enabling and disabling transactions
Annotating a test method with #Transactional causes the test to be run within a transaction that will, by default, be automatically rolled back after completion of the test. If a test class is annotated with #Transactional, each test method within that class hierarchy will be run within a transaction. Test methods that are not annotated with #Transactional (at the class or method level) will not be run within a transaction. Furthermore, tests that are annotated with #Transactional but have the propagation type set to NOT_SUPPORTED will not be run within a transaction.