WebLogic: The Definitive Guide

Development Guidelines

Earlier, we looked at the various types of EJBs supported by WebLogic, and the different circumstances under which you should use them. In this section, we examine some of the important design principles you should adopt when building an enterprise application using EJBs. Careful choices can help you extract the best performance out of your EJBs in a WebLogic environment.

Collocation

The EJB 2.0 standard introduces the notion of local EJBs, which provide lightweight access from other EJBs and local clients running within the same server. An EJB, whose home interface extends EJBLocalHome and whose component interface extends EJBLocalObject, is accessible only to local clients running within the same JVM. Unlike remote EJBs where the client communicates with the EJB over RMI-IIOP, a client can communicate with a local EJB without incurring the overheads of marshalling and unmarshalling associated with remote method calls. Because both the client and the EJB reside within the same JVM, the EJB container is able to use pass-by-reference semantics, similar to an ordinary Java method call.

Consider using local EJBs when you want to ensure they are accessible only to other server-side components or local clients running within the same JVM. This means your local EJB interfaces will not be exposed to other remote clients — i.e., any client running on another JVM, or even another machine. EJBs that participate in container-managed relationships (CMR) with other ...