When an EntityBean (EJB3) is annotated with @PojoCacheable, do I have to explicitely invoke somehow
mycache.put("/myname", myEntityBean) ?
No, @PojCacheable only denotes that this pojo will be instrumented. You will still need to attach it to the cache. However, when running under ejb3, there is container layer integration needed for this to happen. Currently, we are implementing ejb3 sfsb now for PojoCache.
As for entity bean, you should use Hibernate with JBossCache (plaing cache) as a second-level cache.