SCBCD Quick Revision Notes

Enterprise Java Beans (EJB) Overview
There are 3 different types of EJB: session, entity, and message-driven beans. Furthermore, session beans come in two flavors: stateless and stateful.

Client View of a Session Bean
The home interface of a stateless session bean must have only one create() method. This method does not take any arguments.

Session Bean Component Contract
A stateless session bean does not maintain any conversational state.

Session Bean Lifecycle
ejbRemove() will not be invoked if

	The container crashes;
	A system exception is thrown from the session bean instance to the EJB container;
	The client is inactive during a timeout period and the session bean instance is in the PASSIVE state.

Client View of an Entity
The local or remote home interface of an entity bean must include the findByPrimaryKey() method.

Component Contract for Container-Managed Persistence (CMP)
Entity beans cannot use bean-managed transaction demarcation (BMT), that is, there are no BMT entity beans.

Entity Beans
The primary key class for a compound primary key of an entity bean class must be public, all of its member fields must be public, and their names must be a subset of the names of the container-managed fields declared in the deployment descriptor.

EJB-QL
The keyword AS is optional in the FROM clause of an EJB-QL statement.

Transactions
The only valid transaction attributes for message-driven beans are Required and NotSupported.

Exceptions
When an application exception is thrown (only from session or entity bean classes), the current transaction (if any) is not automatically rolled back.

Enterprise Bean Environment
The Deployer must ensure that all <env-entry-value> elements in the deployment descriptor contain appropriate data.

Security Management
The <use-caller-identity> element in the deployment descriptor cannot be used with message-driven beans.