Enterprise JavaBeans 3.1, 6th Edition

The JNDI ENC

The ENC has been around in the EJB specification since the early 1.0 days. It began as a local JNDI namespace that was specific to an EJB container. Developers could define aliases to resources, EJBs, and environment entries in the JNDI ENC through EJB XML deployment descriptors. These aliases could then be looked up directly in JNDI within business logic. In EJB 3.x, this mechanism was enhanced so that JNDI ENC references can be injected directly into the fields of a bean class. Annotations are the primary mechanism for doing this, but XML deployment descriptor support is available for those who wish to use that abstraction.

What Can Be Registered in the JNDI ENC?

Many different items can be bound to the ENC: references to any EJB interface, a JMS queue or topic destination, JMS connection factories, data sources, any JCA resource, and even primitive values. Java EE services such as javax.transaction.UserTransaction, javax.ejb.TimerService, and org.omg.CORBA.ORB are also available in the ENC.

How Is the JNDI ENC Populated?

The ENC’s JNDI namespace is populated in two separate ways: via XML or via annotations. Any reference that you declare in XML to a service or resource automatically populates the JNDI ENC with the reference’s name. Any environment annotation that you use in your bean class also causes the ENC to be populated. Once an item is bound to the JNDI ENC of the EJB container, it can be referenced by a JNDI lookup.

XML population

To illustrate how XML population ...