- An application need to read configurations from an external source, for instance a file
- A configuration file might be changed during an application’s work
If EJB instance, other than Singleton, throws system exception, which is non application runtime exception, then EJB Container immediately discards the instance without calling @PreDestroy method.
This is not a problem if calling @PreDestroy is not essential to an application. If it is, then it was proposed to provide additional application pool of resources or beans and periodically clean up abandoned resources or beans. We do it other way.