Enterprise
Bean Interfaces
- All bean classes must implement javax.ejb.EnterpriseBean, or one of its subinterfaces, at some level.
- Like java.io.Serializable, this is simply a marker interface; it does not define any constants or methods.
- Interestingly, it also extends java.io.Serializable.
- Session beans implement javax.ejb.SessionBean.
- This extends javax.ejb.EnterpriseBean.
- It does define methods:
- ejbActivate, called when the container is going to activate the bean.
- ejbPassivate, called when the container is going to make the bean inactive.
- ejbRemove: when the container is going to terminate the session object.
- setSessionContext, sets the session context, which contains properties of the session.
- You can see that the first three methods are all lifecycle methods, and are called by the EJB container. You can implement these if you want to do something when these life events occur; otherwise, you can simply ignore them.
- Entity Beans implement javax.ejb.EntityBean .
- This also extends javax.ejb.EnterpriseBean.
- Though it does not extend javax.ejb.SessionBean, it has the same methods (though the coutnerpart to setSessionContext is setEntityContext), plus a few more:
- ejbLoad: this is called to instruct the bean to synchronize its state with the underlying database.
- ejbStore: this is called to instruct the bean to store its data in the underlying database.
- unsetEntityContext: unsets the entity context.
- Message Driven Beans implement javax.ejb.MessageDrivenBean. This has two methods: ejbRemove and setMessageDrivenContext.