Is there a function which is called every time an EJB is looked up? I need to refresh some data before any method is called.
+1
A:
Not sure I get exactly what you mean. First you probably need to distinguish between stateless and stateful EJBs.
Stateless EJB are well, stateless, and should not contain data. The app. server can decide to destroy or reconstruct it anytime. You don't actually hold a reference to a particular instance which is created when it's looked up. The app. server maintain a pool of EJBs, and one of them is used per invocation.
Stateful EJB can contain data. You hold a reference to one specific instance, which is created when the bean is looked up. Callback methods can be specified with
@PostConstructor@PreDestroy(These callbacks also exist for stateless EJBs but make less sense).
That said, if you need to perform something before a method is called, I suggest you use an interceptor (using @Interceptor, works for stateless and stateful EJBs). Just like with AOP, you get a chance to perform something before and after the bean method is actually executed, e.g refresh the cache.
ewernli
2010-06-18 10:56:38
Data is client independent so I've created stateless bean (maybe wrongly). I need to read config file before method invocation. This config may change after deployment so I need to update this data everytime someone looks up for my EJB.
Filip
2010-06-18 11:34:58
I see now. Configuration data is not business data, neither it is completely static in your case. I fear that realoding the config each time will be bad performance wise. You could store a timestamp and reload the data if a certain period has elapsed. You can store the config, in an instance field, in a static field, or give a try to a `@Singleton` bean if you use EJB 3.1. An instance field means you will have one config per bean instance, a static field means there is only one config but you must make sure you synchronize things correctly.
ewernli
2010-06-18 11:57:43