Since we're thinking of calling the release 3.1, I started looking at
implementing singleton beans.
Started hacking last night and think I might have something working.
Here are some of my "singleton" spec notes. Perhaps too terse to the
point of being useless, but I figured I'd share anyway.
In general, think stateless bean where there is exactly one instance
(no pool) that is created at startup and never destroyed.
Singletons:
- concurrent access
- session bean
- supports web services
- not activated or passivated
- can use javax.ejb.TimerService
- can have EJBHome/EJBLocalHome interfaces
- With @Startup created when app starts
- @DependsOn allows for startup ordering
- does not support remove
- instances not discarded on system exception
- Bean-Managed or Container-Managed Concurrency
- Container-Managed Concurrency method attributes:
- ReadOnly (shared access)
- ReadWrite (exclussive access), the default
Some related new API classes (subject to change):
- @Singleton (class)
- @Startup (class)
- @DependsOn (class)
- @ContainerManagedConcurrency (class)
- @BeanManagedConcurrency (class)
- @ReadOnly (class, method)
- @ReadWrite (class, method)
- ConcurrentAccessTimeoutException
Will post more details as I get them.
-David
