What is the difference between defining @Transactional on class vs method
In case 1 @Transactional is applied to every public individual method. Private and Protected methods are Ignored by Spring.
Spring applies the class-level annotation to all public methods of this class that we did not annotate with @Transactional. However, if we put the annotation on a private or protected method, Spring will ignore it without an error.
In case 2 @Transactional is only applied to method2(), not on method1()
Case 1:- Invoking method1() -> a transaction is started. When method1() calls method2() no new transaction is started, because there is already one
Case 2:- Invoking method1() -> no transaction is started. When method1() calls method2() NO new transaction is started. This is because @Transactional does not work when calling a method from within the same class. It would work if you would call method2() from another class.
From the spring reference manual:
In proxy mode (which is the default), only external method calls coming in through the proxy are intercepted. This means that self-invocation, in effect, a method within the target object calling another method of the target object, will not lead to an actual transaction at runtime even if the invoked method is marked with @Transactional. Also, the proxy must be fully initialized to provide the expected behaviour so you should not rely on this feature in your initialization code, i.e. @PostConstruct.
@Transactionalon a class applies to each method on the service. It is a shortcut. Typically, you can set @Transactional(readOnly = true) on a service class, if you know that all methods will access the repository layer. You can then override the behavior with @Transactional on methods performing changes in your model. Performance issues between 1) and 2) are not known.
Suppose you have the following class:
@Transactional(readOnly = true)public class DefaultFooService implements FooService { public Foo getFoo(String fooName) { // do something } // these settings have precedence for this method @Transactional(readOnly = false, propagation = Propagation.REQUIRES_NEW) public void updateFoo(Foo foo) { // do something }}The @Transactional annotation on the class level will be applied to every method in the class.
However, when a method is annotated with @Transactional (like, updateFoo(Foo foo)) this will take precedence over the transactional settings defined at the class level.
More info: