are stateless beans thread safe

I am being lazy here - but as I have started reading about EJB some questions come up .

So before I lose track of what doubts I have - I thought would place them here .

So this is an excuse in advance if some one tells me that I am asking them to do my homework !

Are stateless beans threadsafe ?
How does the container go about it ? after the bean is picked from pool - can container use same bean to process multiple requests ?

I am assuming that stateful beans ( since they are per client ) would remain available specific to a client and thereby there cannot be any issues regarding thread safety in case of steful session beans ?

Thanks ,
~satish
[ August 01, 2008: Message edited by: satish bodas ]

Yes, EJBs are threadsafe.

Thanks Paul

I agree with Paul although I think you can make them not thread safe by spawning your own threads, granted in J2EE spawning threads is a really bad idea.

What is a thread-saftiness? If an object is shielded by another object( proxy or container) which serializes concurrent threads, does it make the first object itself thread-safe?

Why in EJB 1.1. and EJB 2.0 it was always highly recommended not to share reference to an EJB among client's threads?

It is used to belive that Entity Beans are thread-safe. Hwo is controlling concurrent access to independent Load and Store methonds? To me, if it is a container, then the Entity Bean itself is NOT thread safe.

In general, I think that from the performace persective, it makes sense to have EJB not thread safe becuase EJB Container can do this job for EJBs. I need to look into EJB 3.0 - how POJO resolves this issue.

Scott Selikoff wrote:I agree with Paul although I think you can make them not thread safe by spawning your own threads, granted in J2EE spawning threads is a really bad idea.

Does that include the case where you inject a stateless EJB in a ServletContextListener with

@EJB FooLocal fooLocal;

and pass it as a parameter to a spawned thread (which has to do some ansynchronous tasks):

MaintencanceThread maintencanceThread = new MaintenanceThread(fooLocal);
t = new Thread(maintenanceThread);
t.setDaemon(false);
t.start();

You are not spawning a thread from the EJB there. That is the part that is specifically precluded by the EJB specification.

Ok, Paul, that's right.

But now suppose that this maintenance thread listens to a ServerSocket for TCP connect requests, and then spawns new threads (using an Executor). Now these threads would all use the same instance of the stateless session bean. That wouldn't be thread-safe, right?