[jboss-user] [EJB3] - How do javax.ejb.Singletons work?

John Lee [https://community.jboss.org/people/jhn134910] created the discussion "How do javax.ejb.Singletons work?" To view the discussion, visit: https://community.jboss.org/message/804718#804718 -------------------------------------------------------------- Are singletons implemented using synchronized methods? I have an EJB singleton, say: @Singleton public void MySingleton {      ...      public void receive(final String string) {           x.callMyBlockingMethod(string);      } } Consider the scenario, where this is running in JBOSS standalone. This singleton shall be called from multiple threads, with names Thread-1, Thread-2 and Thread-3 in that order. Thread-1 calls the blocking method which doesn't return for 10 seconds. Thread-2 arrives at the receive method shortly after Thread-1, followed shortly by Thread-3 and both wait for the lock to be released by Thread-1. Is there anything in the EJB standard regarding singletons that guarantees that Thread-2 shall aquire the lock before Thread-3 once Thread-1 releases it? I'm going to test this singleton behaviour but if my test shows that Thread-2 is indeed processed before Thread-3 and order is maintained, it shall not tell me that this is guaranteed behaviour, and is merely a consequence of using a particular OS, JVM or EJB container implementation. So does @Singleton offer any guarantees? If it does, are there any gotchas about using this behavior to queue up client requests against singleton where they wait to acquire the lock? -------------------------------------------------------------- Reply to this message by going to Community [https://community.jboss.org/message/804718#804718] Start a new discussion in EJB3 at Community [https://community.jboss.org/choose-container!input.jspa?contentType=1&...]