Question

I have a method that will be used to send out email. i want to lock this method so only one thread can accses it per time and the rest pool up concurrently. should i synchronized the method or use spring @transactional PROPAGATION_REQUIRED ?

in my service layer

 //each time use new thread to send out email
  public  void sendThroughSMTP(List<String> emails,String subject,String content){

            //each time will open and sent through port 25.  dont u think this will caused too many threads spawned?
            BlastEmailThread blastEmailThread = new BlastEmailThread(emails,subject,content);

            blastEmailThread.start();


}

Answer 1

Why not make the method thread-safe by not using any instance level things?

However, I don’t see how Spring’s Transaction Management fits here. I mean Spring provides few transaction managers, i.e. DataSourceTransactionManager, JtaTransactionManager, HibernateTransactionManager all this is about database persistence. What will you configure for this email send out?

I believe, first you should show us why you worry about the thread-safety in the first place. Most probably you would like to show us some relevant code snippet or something. Then we might be able to suggest you something.

[Addendum]

When you are spawning a thread for every call to that method and not using anything from the state, then why you want to make the method synchronized. Making the method synchronized will not limit the number of threads in any way. There might be chance that before starting a new thread, previous thread might have finished the work, because of synchronization. The process of spawning a thread might go slower.

However, you should go with this until you find out that there are really many threads running and you are going out of memory. And if you really want to tackle that before time, then you should choose some blocking mechanism, something like Semaphore.