How EJB evolved over the years?

The evolution of EJB can be captured in following points:
1.0:

- No mandate that Entity EJB must be supported by EJB container
- EJB communication backbone uses RMI-JRMP(Java Remote Method Protocol)
- No CMP Entity EJB
- No Deployment Descriptor XML file, used compiled class, then serializes it into flat file (binary).
1.1:
- Entity Bean supported by EJB container
- has CMP, but never describe how to configure relationship between CMP Entity EJBs, this depends on container tool provided by vendor
- RMI-IIOP is suggested for EJB communication
- Deployment Descriptor XML file was introduced
2.x:
- Message Driven Bean is introduced
- With CMP, you can configure the relationship between CMP Entity EJBs, in ejb-jar.xml
- EJB-QL for CMP EntityEJB query language
- RMI-IIOP is a must for EJB communication
3.0:
-No more deployment descriptor,metadata annotations used instead.
-CMP simplified.It is more like JDO or Hibernate.
-Checked exceptions are reduced.RemoteException is no longer mandatory with each remote business method .
-Inheritance is allowed and a bean can extend some base code.
-EJB-QL enhanced.

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