The Business Tier

All of these classifications are more important to application developers than to administrators/ deployers .

Most EJBs are prebundled as a module for deployment. Geronimo administrators and deployers work with a bundled archive rather than individual EJBs.

An important thing to realize from Figure 4-3 is that entity beans may require the configuration of a Java Database Connectivity (JDBC) data source for storing the related data, and deployment of MDBs may require the configuration and setup of a JMS destination. Of course, code within the EJB implementation may also reference other business-tier EJBs that may not reside within the same archive bundle.

Deployable Module at Geronimo’s Business Tier

EJBs to be deployed to the Geronimo server must be bundled in an EJB JAR file. According to the J2EE 1.4 specifications, the EJBs must be bundled together with a standard deployment descriptor called ejb-jar.xml , placed in the META-INF directory of the archive.

Deploying EJBs As Part of an Enterprise Application

Most likely, especially in production, the EJBs in an EJB JAR file is just a part of a larger enterprise application. In this case, a WAR file (for the Web-tier components) is combined with an EJB JAR file to create a new archive called an E nterprise A pplication A r chive, or an EAR file. An EAR file is just a JAR file with an .ear extension.

An EAR file can contain one or more WAR files containing servlets and JSPs, and one or more JAR files containing EJBs (as well as other resource adapter JARs). It must include a standard deployment descriptor, called application.xml , in the META-INF directory. This deployment descriptor should reference the modules that are a part of the overall enterprise application.

OpenEJB at the Business Tier

The EJB container inside Geronimo is a special version of the OpenEJB version 2.1 container. OpenEJB is an Open Source EJB container, hosted at Codehaus, that is released under the Apache 2.0 license. For more information on OpenEJB , see:

http://openejb.codehaus.org/

The OpenEJB container integration within Geronimo features the following:

• Support of EJB 2 Container Managed Persistence 2

• Support of EJB QL

• Support of EJB 2.1 Web services interoperation

• CORBA interoperation

The specially adapted OpenEJB container inside Geronimo makes full use of Geronimo’s container services. This includes JNDI support, fully configurable transactional support and security.

Chapter 12 will provide detailed information on the configuration and deployment of EJBs (either alone in an EJB JAR or as a part of an EAR) to the OpenEJB container.