Hibernate LockMode expected behavior - spring

Question

#Repository
public class MyClass{
public int myFunction(Integer id){
Record x = recordDao.get(id,LockMode.UPGRADE);
int d = x.getProp();
x.setProp(d+1);
recordDao.update(z);
}
}
#Service
#Transactional
public class MyOtherClass{
#Autowired
private MyClass myClass;
public void myOtherFnx(Integer id){
try{
myClass.myFunction(id);
}catch(Exception e){
throw new RuntimeException(e.getMessage());
}
}
}
What happens when new MyOtherClass().myOtherFnx(3) was invoked at same time but at separate request/transactions.
I tried creating runnables and invoke myOtherFunx on separate threads to simulate concurrency. I was expecting to get RuntimeException but
so far I haven't notice getting any runtime exception even if i increase the threads running myOtherFunx to 50.
Can you explain to me why this happens? Or is my assumption that a runtime exception will occur. The case when I am expecting a runtime exception
is when multiple threads invoke myClass.myFunction(3) and the Record object retrieved on these threads are the same, let's say
id=3,prop=4. Since one of them gets the lock first, when threads try to update the record only one should update and others will throw exception since I am catching all Exception.

Answer 1

The first Thread will acquire the lock, and release it on commit or rollback.
While the first Thread is doing its work, the rest of threads will wait for the lock to be released.
After the lock has been released, the next Thread will acquire it, do the updates, commit, and so on...
If you want to get an exception, you will have to use the LockMode UPGRADE_NOWAIT.