1.3. Getting inside EJB

When you build a simple Java class, you need a Java Virtual Machine (JVM) to execute it. In a similar way (as you learned in the previous section) to execute session beans and MDBs you need an EJB container, and to run your entities you need a persistence provider. In this section we give you a bird’s-eye view of containers and persistence providers and explain how they are related.

In the Java world, containers aren’t just limited to the realm of EJB 3. You’re probably familiar with a web container, which allows you to run web-based applications using Java technologies such as servlets, JSP, or JSF. A Java EE container is an application server solution that supports EJB 3, a web container, and other Java EE APIs and services. BEA WebLogic Server, Sun Microsystems’s GlassFish, IBM WebSphere, JBoss Application Server, and Oracle Application Server 10g are examples of Java EE containers. The relationship between the Java EE container, web container, EJB container, and JPA persistence provider is shown in figure 1.7.