What is the difference between defining @Transactional on class vs method
Case1
@Transactional
public class UserServiceImpl implements UserService {
...................
public void method1(){
try{
method2();
}catch(Exception e){
}
}
public void method2(){
}
}
Case2
public class UserServiceImpl implements UserService {
...................
public void method1(){
try{
method2();
}catch(Exception e){
}
}
@Transactional
public void method2(){
}
}
In case1 if any exception occurs it rollback is working, but in case 2 it's not working. Is there any performance issues if I follow the case1?
Answer
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.