Generally, SLSBs are generated in managed pools by the container. So a single thread can access a single instance of a SLSB at a time. But the container can create as many copies as it wants (ie, a pool of them) to handle all incoming threads. Since a SLSB is truly a stateless service (or should be!), any single instance of that bean can handle any request from any thread. In this regard, stateless session beans are considered thread-safe. And to reiterate, thread usage within an EJB is considered a no-no.
Cheers
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