Enterprise JavaBeans 3.0, 5th Edition

Chapter 3. Resource Management and Primary Services

Chapter 2 discussed the basic architecture of Enterprise JavaBeans and Java Persistence, including the relationship between the bean class, the EJB container, and the EntityManager service. These artifacts define a common model for distributed server-side components as well as a persistence model that can be used on the server or in standalone applications. But this model isn’t enough to make EJB interesting or even particularly useful. EJB servers also manage the resources used by beans, and can manage thousands or even millions of distributed objects simultaneously. They must manage how distributed objects use memory, threads, database connections, processing power, and more. Furthermore, the EJB specification defines interfaces that help developers take advantage of these common practices.

EJB servers support six primary services: concurrency, transaction management, persistence, object distribution, naming, and security. These services provide the kind of infrastructure that is necessary for a successful three-tier system. EJB also supports two additional services: asynchronous messaging and a timer service.

This chapter discusses the resource-management facilities and the primary services that are available to Enterprise JavaBeans.

Resource Management

A large business system with many users can easily have thousands or even millions of objects in use simultaneously. As the number of interactions among these objects increases, ...