WebLogic: The Definitive Guide

Getting Started

Before we delve into the configuration of the various EJB types, it is useful to understand under which circumstances the different EJB types should be used. After this, we provide an overview of how to package your EJBs, and how to use the deployment descriptors to configure the runtime behavior of your EJBs. We also describe how you can use WebLogic’s tools to generate and compile the classes needed to deploy your EJBs. Finally, we look at how to set up references to other EJBs and resources.

EJB Types

WebLogic provides full support for the different component models: session beans that model business processes, entity beans that model domain entities, and message-driven beans (MDBs) that represent asynchronous message consumers. Here’s a quick summary of important characteristics of these three EJB types:

Session beans

• A session bean executes on behalf of a single client.

• It typically accesses or updates shared data in the underlying database.

• It supports both container-managed and bean-managed transactions.

• The EJB container supports a pool of stateless session EJB instances that can be shared across multiple clients. It also supports a cache of stateful session EJB instances, where each instance maintains the conversational state for a specific client.

Consider using a session bean when only one client can have access to an EJB instance, and session state is relatively short-lived and need not be persisted. Consider using a stateful bean if the EJB holds session information ...