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Enterprise JavaBeans: Getting Started with EJB, Part 4

  • January 3, 2001
  • By Richard G. Baldwin
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Java Programming, Lecture Notes #1313


Preface

This is one in a series of lessons designed to teach you about Sun's Enterprise JavaBeans (EJB).

This lesson is also the fourth lesson in a miniseries intended to get you up and running with Sun's Enterprise JavaBeans(TM) very quickly.

Preview

The following steps are required to deploy your bean into the J2EE server:
  • Create the J2EE Application
  • Package the Enterprise Bean
  • Deploy the J2EE Application
This lesson will show you how to accomplish the first of the three steps listed above.

Along the way, you will learn how to start and stop the J2EE server.  You will learn how to expose the J2EE options, and you will learn how to start the deploytool program.

You will get your first look at the deploytool GUI and use it to create your application.

Introduction

Writing, compiling, deploying and executing a simple bean

The lessons in this miniseries will show you the steps involved in writing, compiling, deploying and executing a simple bean.  The discussion will be brief, and is intended primarily to get you to the point that you can get something running very quickly.

More details in subsequent lessons

Subsequent lessons will come back and fill in the gaps to help you more-fully understand each of the steps.

Subsequent lessons will also teach you about the different kinds of beans and how to use those beans in different situations.

Recommended supplementary reading

It is strongly recommended that you study the previous lesson entitled Enterprise JavaBeans: Getting Started with EJB, Part 3

before embarking on this lesson.

Additional supplementary material that I have written is available at Gamelan.  As of the date of this writing, Gamelan does not maintain a consolidated index to my Java tutorials.  Therefore, they may be difficult to locate on the Gamelan site.  A consolidated index with links to the tutorials on the Gamelan site is available at Baldwin's Java Programming Tutorials.

The required steps

An earlier lesson entitled Enterprise JavaBeans: Getting Started with EJB, Part 1

contained a list of the required steps for writing, compiling, deploying and executing a simple bean.  Abbreviated versions of the first seven steps in that list are repeated below.

  • Download and install Java 2 Platform, Standard Edition from Sun.
  • Download and install the Java 2 Platform, Enterprise Edition.
  • Write the bean class and required helper classes.
  • Write home and remote interfaces.
  • Write a compilation batch file for the bean and the interfaces.
  • Compile the bean class, helper classes, and interfaces.
  • Use Sun's J2EE deploytool program to deploy the bean into the server.
Class files available

The first six steps were discussed in earlier lessons, and I am assuming that you have completed those steps.  Having completed them, you should have the class files necessary to deploy your bean into the J2EE server.

Deployment of the bean is the subject of the last step in the above list, and is also the topic of this lesson.

Watch that last step, it's a big one

The last step shown above is a big one, so I have subdivided it into several sequential lessons, beginning with the previous lesson entitled Getting Started with EJB, Part 3.

The detailed steps

In this group of lessons associated with deployment, I am walking you through the detailed steps necessary to deploy your new bean in the J2EE server.  Those steps are:

  • Create the J2EE Application
  • Package the Enterprise Bean
  • Deploy the J2EE Application
I am providing instructions for accomplishing those three steps in cookbook fashion, meaning that I will tell you what to do but not necessarily why to do it.

This lesson deals with the first of the three steps.

Viewing tip

Deploying a bean can be very tedious and a little complex.  This and the following lessons provide screen shots of the critical steps in the process.  You may find it useful to open another copy of this lesson in a separate browser window.  That will make it easier for you to scroll back and forth and refer to earlier material and figures, without losing your place.

Beans versus beans

Just in case you are reading this lesson without having read the earlier lessons in this series, I will tell you that an enterprise bean is not the same thing as a JavaBean Component(TM), as discussed in my series of tutorial lessons beginning with lesson number 500.

Sample Bean Program

Class files

At this point, you should have the following three class files as a result of compiling the bean class and the two interfaces during previous lessons.  Make sure that you have them all located conveniently in the same directory.

  • HelloBean.class
  • HelloHome.class
  • Hello.class
The first of these is the class file for the bean proper.  The second is the class file for the home interface.  The third is the class file for the remote interface.

A complete listing of the bean program and the two required interfaces is provided near the end of this lesson.

Creating the J2EE Application

As described in the previous lesson, you do not deploy an enterprise bean directly into the J2EE server.  Rather you must first create a J2EE application and then add the bean to the J2EE application.  Then, you then deploy the application into the J2EE server.

Step-by-step instructions

This lesson will contain the step-by-step instructions for creating a new J2EE application named HelloApp and for storing the application in a file named HelloApp.ear.

Windows NT

These instructions are written for use with a Windows NT operating system.  If you are using some other operating system, you will need to translate these instructions into the terminology of that operating system.

Get two Command Prompt windows

The first thing that you need to do is to open two Command Prompt windows.  If you know how to use the JDK from Sun for compiling and executing Java applications at the command line, you already know how to do this.

If you don't know how ...

If you don't already know how to do it, you should be able to open the Start menu (on the lower left of your screen) and then select Programs.  There you should find an entry for Command Prompt.  Choose that entry to open the window.  Do this twice to open two separate windows.

From here on, I will refer to the Command Prompt windows simply as windows.

Start the J2EE server

To start the J2EE server running, enter the following command at the prompt in one of the windows:

j2ee -verbose

The -verbose parameter causes output from the server to be displayed in the window where the server is running.  If you leave it off, output from the server will be sent to a log file.

The screen output

Listing 1 is a partial screen shot of the kinds of information that you should see on your screen as the server starts and progresses to the ready state.  For brevity, I have deleted several lines of material in the middle of the sequence and have replaced those lines with ...  I also inserted some manual line breaks to force the material to fit in this narrow format.
 

C:\jnk>j2ee -verbose

J2EE server Listen Port: = 1049
Naming service started: :1050
Published the configuration object ...
Binding DataSource, name = jdbc/Cloudscape, 
url = jdbc:cloudscape:rmi:Cloudscape
B;create=true
Web service started: 9191
Web service started: 8000
Web service started: 7000
Loading
...

J2EE server startup complete.

Listing 1

The last line is critical

The critical thing to note is that the last line shown above should appear indicating that the server is ready.  If it doesn't appear, there is no point in starting the deployment tool (as described later).

No prompt should appear

The prompt should not reappear until you stop the server.  If the prompt does reappear, it will probably be preceded by an error message of some sort indicating that the server did not start running properly.

J2EE options

You can learn more about the J2EE options by entering the parameter -? as shown by the (reformatted) screen shot in Listing 2,
 

C:\jnk>j2ee -?

Java 2 Enterprise Edition Server
Options:
-verbose   Redirect all logging output to
           the current shell.
-help      Print this help message.
-version   Print the version.
-singleVM  Deploys all beans in this process.
-multiVM   Deploys all beans in a jar file
           in a new process.

-stop      Stop the J2EE server.

Listing 2

Stopping the server

As you can see, to stop the server, you must enter j2ee -stop in a different window.  When you do that, the prompt will reappear in the window in which the server is running.

The J2EE version

Entry of j2ee -version while writing this lesson produced the following output.

Java 2 Enterprise Edition version 1.2.1

Thus, the deployment instructions that follow in this and subsequent lessons are based on version 1.2.1.

Using later versions of J2EE

As new versions of J2EE are released, adjustments may need to be made to these instructions, depending on the changes that are made in succeeding versions of J2EE.  Hopefully the product will remain sufficiently stable that these instructions will continue to be a useful guide in getting your first enterprise bean up and running, even for later versions of J2EE.

Starting the deployment tool

Once the server has been started successfully, you need to start the deployment tool.  To do this, enter the following command at the prompt in another window:

deploytool

The main deployment screen

A splash screen will appear first.  This will be followed by a screen that looks similar to Figure 1.  This is the main deployment screen.

This screen is a very large dialog box with dimensions of 841 x 736 pixels, so I had to reduce it considerably to make it fit in this format.

Previously deployed applications

The tall rectangular area on the left in Figure 1 contains a tree display showing previously deployed applications.  When you deploy your first application, this frame will initially be empty.  As you deploy new applications into the server, they will appear in this frame each time you start the deployment tool running.

Figure 1. The J2EE deployment tool main screen.

Additional screen shots

I will supplement the deployment instructions with screen shots like Figure 1 at critical points in the process.  Because of the need to reduce the image for display, you often won't be able to read the text in the screen shots.  However, I believe that the screen shots will help you make sure that you are at the right place in the deployment process.

Color coded for clarity

The following text will be a mixture of action statements and explanatory text.  I will color the actions statements the following color of blue to make them easy to separate from the explanatory text.

Create your new J2EE application

Here are the steps for creating your new application using the deployment tool:

  • Select the File menu.  A pulldown menu will appear.
  • Choose New Application in the pulldown file menu.
  • Click Browse.  A file chooser will appear.
  • In the file chooser, locate the directory where you want to place the .ear file that contains the J2EE application.
  • Enter HelloApp.ear in the File name field.
  • Click New Application.  This causes a smaller dialog box to appear showing the path and name of your ear file in one text field and the ApplicationDisplayName in a second text field.
  • Click OK to accept these two names.
Your new application is still empty

Your new application has now been created, but at this point it is empty.  If you are monitoring the directory specified as the location of the ear file, you should notice that a file named HelloApp.ear has appeared in that directory.

Back to main deployment screen

At this point, you should be back to the screen shown in Figure 1.  You can terminate the deployment tool by selecting Exit from the file menu.  You can also terminate the server by entering j2ee - stop in a window other than the window in which the server is running.

Summary

The following steps are required to deploy your bean into the J2EE server:
  • Create the J2EE Application
  • Package the Enterprise Bean
  • Deploy the J2EE Application
This lesson has provided instructions for accomplishing the first step.  Along the way, you learned how to start and stop the J2EE server.  You learned how to expose the J2EE options, and you learned how to start the deploytool program.  You got your first look at the deploytool GUI and used it to create your application.

Where To From Here?

The next lesson will walk you through the second of the three steps listed above:  Package the Enterprise Bean.

Complete Program Listings

A complete listing of the bean program is shown in Listing 3 below.  Complete listings of the remote and home interfaces are shown in Listing 4 and Listing 5.
 
/* File HelloBean.java
Copyright 2000 R.G.Baldwin
Rev 9/15/00

This bean receives and returns a String object
via a single business method.  It also displays
information about its life cycle in the 
System.out log file or on the system comsole
depending on whether or not System.out has been
directed to the log files.

This is a stateless session bean.  According to
Sun, a session bean must meet the following
reuirements:

Implement the SessionBean interface.
Class is defined as public.
Class cannot be defined as abstract or final.
Implements one or more ejbCreate methods.
Implements the business methods.
Contains a public constructor with no 
  parameters.
Must not define the finalize method.

Tested using Sun j2ee and JDK 1.3 under 
WinNT 4.0 workstation.
***********************************************/
import javax.ejb.*;
import java.util.Date;

public class HelloBean implements SessionBean{
  SessionContext ctx;

  public void ejbCreate(){
    System.out.println("HelloBean Created " 
                                  + new Date());
  }//end ejbCreate()

  public String aBusinessMethod(String str){
    return "Hello " + str;
  }//end aBusinessMethod()

  public void ejbRemove(){
    System.out.println("HelloBean Removed " 
                                  + new Date());
  }//end ejbRemove()

  public void ejbActivate(){
    System.out.println("HelloBean Activated " 
                                  + new Date());
  }//end ejbActivate()

  public void ejbPassivate(){
    System.out.println("HelloBean Passivated " 
                                  + new Date());
  }//ejbPassivate()

  public void setSessionContext(
                            SessionContext ctx){
    this.ctx = ctx;
    System.out.println(
      "HelloBean got SessionContext " 
                                  + new Date());
  }//setSessionContext()

  public HelloBean(){}//public constructor

}//end class HelloBean
 

Listing 3


 
/* File HelloHome.java 
Copyright 2000 R.G.Baldwin
Rev 9/15/00
***********************************************/
import javax.ejb.*;

public interface HelloHome extends EJBHome{
  public Hello create()
                throws java.rmi.RemoteException, 
                      javax.ejb.CreateException;
}//end interface

Listing 4


 
/* File Hello.java
Copyright 2000 R.G.Baldwin
Rev 9/15/00
***********************************************/
import javax.ejb.*;
import java.rmi.*;

public interface Hello extends EJBObject{
  String aBusinessMethod(String s)
                         throws RemoteException;
}//end interface

Listing 5


Copyright 2000, Richard G. Baldwin.  Reproduction in whole or in part in any form or medium without express written permission from Richard Baldwin is prohibited.

About the author

Richard Baldwin is a college professor and private consultant whose primary focus is a combination of Java and XML. In addition to the many platform-independent benefits of Java applications, he believes that a combination of Java and XML will become the primary driving force in the delivery of structured information on the Web.

Richard has participated in numerous consulting projects involving Java, XML, or a combination of the two.  He frequently provides onsite Java and/or XML training at the high-tech companies located in and around Austin, Texas.  He is the author of Baldwin's Java Programming Tutorials, which has gained a worldwide following among experienced and aspiring Java programmers. He has also published articles on Java Programming in Java Pro magazine.

Richard holds an MSEE degree from Southern Methodist University and has many years of experience in the application of computer technology to real-world problems.

baldwin.richard@iname.com






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