This chapter looks at one of the principal types of component in the Java 2 Platform, Enterprise Edition (J2EE) — Enterprise JavaBeans (EJBs). See how EJBs are applied and how they are deployed. (This is chapter 4 from Sams Publishers, author Martin Bond, et. al., Teach Yourself J2EE in 21 Days, second edition, ISBN: 0-672-32558-6).
In this section, you will look at how to deploy an EJB in the J2EE Reference Implementation (RI) and how to run the simple application client.
Configuring J2EE RI
On Day 2 you were asked to install and configure the J2EE RI available, free of charge, from Sun Microsystems (at http://java.sun.com/j2ee) and build a sample database for the exercises in this book. If you have not already done so go back to Day 2 and follow the instructions for installing the J2EE RI and building the Agency case study database.
Note - As discussed on Day 2, before running any of the tools described in this section, you will need to set the J2EE_HOME environment variable to the location on your hard drive where you installed the J2EE reference implementation. You should also add the bin directory below J2EE_HOME to your executable search path (%PATH% under Windows or $PATH under Solaris/Linux) so that you can run J2EE tools and batch files from the command line. You should place the J2EE bin directory at the front of your PATH setting to avoid conflicts with system tools with the same names as the J2EE tools. You should also copy the code in the CaseStudy directory on the accompanying Web site onto your local hard disk, because commands you will run today require write access to the working directory.
There are two approaches to building and deploying a J2EE component or application using J2EE RI:
You can use the deploytool provided with the J2EE SDK.
You can use the asant utility supplied with the J2EE SDK (this is a modified version of the popular Apache Ant utility from http://jakarta.apache.org/ant). The J2EE tutorial examples for J2EE SDK 1.4 are built and deployed using asant build files and asant build files are supplied for all the examples used throughout this book.
As a newcomer to J2EE, you will find it informative to use the GUI interface of deploytool for building and configuring the EAR and WAR files used to hold your EJBs, applications, and web components. As you gain more experience, you might find the speed of the asant command-line interface to be preferable. You will also find asant build files useful for scripting automated testing procedures.
The disadvantage of using asant is that you will have to write the build files yourself; not to mention hand crafting all the deployment descriptors. Many developers use deploytool once to generate the basic deployment descriptors and then save these descriptors to disk for use with asant build files. That is how most of the examples for this book were developed.
This section will show how to build and deploy J2EE components using deploytool before looking at the asant build files used for the Agency case study example. The directory structure for the book's example code was discussed on Day 2, but as a quick reminder, these are the subdirectories under the exercise directory for Day 4:
build—A temporary directory used by the asant build files (created when needed)
classes—The compiled class files
dd—The deployment descriptor files used by the asant build files
j2ee-ri—Repository for files manipulated by deploytool
src—The Java source files
JSP—The HTML and JavaServer Pages source files
Remember to make sure you are running the J2EE RI server and PointBase database servers and have created the Agency database before starting this exercise.
Opening the Case Study EAR File
Now you are ready to run the deploytool found in the bin directory under the J2EE_HOME directory. Start a command line window in the Day04/exercise directory and enter the command:
You will be presented with a graphic interface for building J2EE components. If you have not set your PATH to include the bin directory under J2EE home you will have to provide the full pathname for deploytool. Windows users can use the Start, Programs, Sun Microsystems, J2EE 1.4 SDK, Deploytool menu or run
Solaris and Linux users should enter
In deploytool, use the File, Open menu to open the supplied agency enterprise archive (EAR) file in Day04/exercise/j2ee-ri/agency.ear. The agency application will now be displayed in the list of applications, as shown in Figure 4.2.
Figure 4.2 The Agency application loaded by deploytool.
This chapter is from Teach Yourself J2EE in 21 Days, second edition, by Martin Bond et. al. (Sams, 2004, ISBN: 0-672-32558-6). Check it out at your favorite bookstore today. Buy this book now.