Chapter 14 Working with Java

Defining EJBs

Introduction

The Java TM 2 Platform, Enterprise Edition (J2EE TM) is a Java platform that defines the standard for developing multi-tier enterprise applications. J2EE simplifies enterprise applications by basing them on standardized, reusable modular components, it provides a complete set of services to those components, and handles many details of application behavior automatically without complex programming.

Java 2 Enterprise Edition supports the following technologies that you can use in PowerDesigner:

Enterprise JavaBean (EJB)
Java Servlets (Servlets)
Java Server Page (JSP)

The following sections develop how to use these technologies in PowerDesigner.

EJB

Sun Microsystems definition of Enterprise JavaBeans TM is:

"The Enterprise JavaBeans architecture is a component architecture for the development and deployment of component-based distributed business applications. Applications written using the Enterprise JavaBeans architecture are scalable, transactional and multi-user secure. These applications may be written once and then deployed on any server platform that supports the Enterprise JavaBeans specification".

EJBs are non-visual, remotely executable components that can be deployed on a server, they provide a component architecture framework for creating distributed n-tier middleware. They communicate with clients to make some services available to them.

Enterprise JavaBeans enable rapid and simplified development of distributed, transactional, secure, and portable Java applications. EJB servers reduce the complexity of developing middleware by providing automatic support for middleware services such as transactions, security and database connectivity.

For more information on EJB, a specification is available from Sun Web site, at http://java.sun.com

PowerDesigner supports the EJB 2.0 specification, with special emphasis on entity beans (both CMP and BMP). PowerDesigner implementation of EJB support can take full advantage of the tight integration between PDM and OOM.

What do you need to work with EJBs?

You need Java 2 SDK Standard Edition (J2SE TM) 1.3 (final release), Java 2 SDK Enterprise Edition (J2EE TM) 1.3 (final release), a Java IDE or a text editor. You also need a J2EE application server supporting EJB 2.0.

It is also recommended that you set up the JAVA_HOME and J2EE_HOME system variables in your environment as follows:

In CLASSPATH:

%JAVA_HOME%\lib;%J2EE_HOME%\lib\j2ee.jar;%J2EE_HOME%\lib

In Path:

%JAVA_HOME%\bin;%J2EE_HOME%\bin