In the singleton section (4.8.3) of the ejb 3.1 specification it is stated like the following-
「4.8.3Transaction Semantics of Initialization and Destruction
PostConstruct and PreDestroy methods of Singletons with container-managed transactions are transactional.
From the bean developer's view there is no client of a PostConstruct or PreDestroy method.
A PostConstruct or PreDestroy method of a Singleton with container-managed transactions has transaction
attribute REQUIRED, REQUIRES_NEW, or NOT_SUPPORTED (Required , RequiresNew, or NotSupported if the deployment descriptor is used to specify the transaction attribute).
Note that the container must start a new transaction if the REQUIRED (Required) transaction attribute is used. This guarantees, for example, that the transactional behavior of the PostConstruct method is the same regardless of whether it is initialized eagerly at container startup time or as a side effect of a first client invocation on the Singleton. The REQUIRED transaction attribute value is allowed so that specification of a transaction attribute for the Singleton PostConstruct/PreDestroy methods can be defaulted.」
Can anyone please put some light about the necessity of container managed transaction only for singleton lifecycle callback methods. For stateless session beans nothing like the above takes place. So, why for singleton this is required.
An example in the answer will be highly appreciated.