Home > Articles > Software Development & Management

  • Print
  • + Share This
Like this article? We recommend

An Example EJB3 Project on JBoss5

The example program is a simple EJB3 stateless session bean. When we’re through with the code, you’ll have seen some of the following:

  • Persistence coding with JPA
  • The components of EJB3
  • The concept of an entity bean
  • Stateless session beans
  • Running a client program

The application is very simple indeed. I model a greeting card entity that has a message and a color. Both of these attributes can be modified from the client program. The finished greeting card entity is stored in the default JBoss5 database. Before you can run the example code, you’ll have to download the code zip file and extract it into a folder such as the following:

C:\ejbcode

Next, set up the environment variables as described earlier. Run any Ant targets from the folder containing the Ant script file: build.xml. Let’s now have a look at the Java code.

The Domain Model

Listing 1 illustrates the domain entity that models our greeting card. Notice the use of annotations, such as @Entity and @Table. You might remember these if you read my recent article about JPA and Hibernate.

Listing 1 The Domain Entity for a Greeting Card

@Entity
@Table(name="GREETING_CARD")
public class GreetingCard implements java.io.Serializable
{
  private int id;
  private String greeting;
  private int colour;

  @Id
  @Column(name="ID")
  public int getId() {
  return id;
  }

  public void setId(int pk) {
  id = pk;
  }

  @Column(name="NAME")
  public String getGreeting() {
    return greeting;
  }

  public void setGreeting(String str) {
  greeting = str;
  }

  @Column(name="COLOUR")
  public int getColour() {
  return colour;
  }

  public void setColour(int colour) {
  this.colour = colour;
  }
}

One of the first things that struck me about EJB3 code is its brevity. Listing 1 models a business entity. How do you choose such entities? A good rule of thumb is to model the entities described as nouns in your business domain. So, our code will be using instances of the entity in Listing 1—reading and writing them to the database. Let’s now look at the EJB interface—this is the so-called business contract.

The EJB Interface

The interface is the business contract and is illustrated in Listing 2.

Listing 2 The Business Interface

import javax.ejb.Remote;

import com.cardsrus.domain.GreetingCard;

@Remote
public interface CardShopRemote
{
  public void createGreetingCard(GreetingCard greetingCard);
  public GreetingCard findGreetingCard(int pKey);
  public void removeGreetingCard(GreetingCard greetingCard);
  public void mergeGreetingCard(GreetingCard greetingCard);
  public void flushGreetingCard();
}

The use of the @Remote annotation indicates that the implementation of this interface is accessible to clients outside the EJB3 container. Don’t think of this interface as being any more complex than a normal Java interface; it just has a set of methods that can be implemented by a bean class. Let’s now look at such an implementation—our first bean.

The Bean Class

Listing 3 illustrates the stateless bean class. This class implements the interface we saw in Listing 2.

Listing 3 The bean Class

@Stateless
public class CardShopBean implements CardShopRemote
{
  @PersistenceContext(unitName="cardshop") private EntityManager manager;

  public void createGreetingCard(GreetingCard greetingCard) {
  manager.persist(greetingCard);
  }

  public GreetingCard findGreetingCard(int pKey) {
  return manager.find(GreetingCard.class, pKey);
  }

  public void removeGreetingCard(GreetingCard greetingCard) {
  manager.remove(greetingCard);
  }

  public void flushGreetingCard() {
  manager.flush();
  }

  public void mergeGreetingCard(GreetingCard greetingCard) {
  manager.merge(greetingCard);
  }
}

The most noteworthy thing in Listing 3 is the use of the EntityManager class. This is required to gain access to the database services. The next building block is the client program.

The Client

Listing 4 illustrates the client class that brings it all together.

Listing 4 The client Class and Main Program

public class Client
{
  public static void main(String [] args)
  {
    try
  {
      Context jndiContext = getInitialContext();
      Object ref = jndiContext.lookup("CardShopBean/remote");
      CardShopRemote dao = (CardShopRemote)ref;

      GreetingCard oldGreetingCard = dao.findGreetingCard(1);
      if (oldGreetingCard != null)
      {
      dao.mergeGreetingCard(oldGreetingCard);
      dao.removeGreetingCard(oldGreetingCard);
      dao.flushGreetingCard();
      }

      GreetingCard greetingCard_1 = new GreetingCard();
      greetingCard_1.setId(1);
      greetingCard_1.setGreeting("Seasons Greetings from Terry Dactyll");      greetingCard_1.setColour(1);

      dao.createGreetingCard(greetingCard_1);

      GreetingCard greetingCard_2 = dao.findGreetingCard(1);
      System.out.println(
"Greeting card name:"+greetingCard_2.getGreeting());
      System.out.println(
"Greeting card colour: " + greetingCard_2.getColour());
    }
    catch (javax.naming.NamingException ne)
    {
    ne.printStackTrace();
  }
  }

  public static Context getInitialContext()
    throws javax.naming.NamingException
  {
    return new javax.naming.InitialContext();
  }

The program is divided into four main sections:

  • Resource lookup
  • Deleting old greeting cards
  • Creating a new greeting card
  • Retrieving the new greeting card

Again, notice the simplicity of the code. In spite of the compact size and simplicity, the code in Listing 4 is doing some pretty sophisticated stuff: JNDI lookups, database access, entity creation, entity modification, etc. However, the code conceals much of the complexity because it effectively “outsources” the mechanics to the EJB3 container.

The last major code element is the persistence unit. Let’s look at this now.

The Persistence Unit

The last major building block you need is what’s called the persistence unit. Just think of this as the database that the Java code uses. This is the location into which instances of the domain entities are written and retrieved. You might have heard of an acronym called CRUD? This is Create, Read, Update, and Delete, and represents the typical set of database operations you execute on your data. You create new entity instances. You read these instances from the database. You modify or update existing entities. Finally, when you no longer need a given entity, you delete it. Well, the client code in Listing 4 illustrates the CRUD operations, and the persistence unit (see Listing 5) describes the data source against which these operations take place.

Listing 5 The Persistence Unit XML File

<?xml version="1.0" encoding="UTF-8"?>
<persistence
  xmlns="http://java.sun.com/xml/ns/persistence"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
  version="1.0"> 

  <persistence-unit name="cardshop">
   <jta-data-source>java:/DefaultDS</jta-data-source>
   <properties>
     <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
   </properties>
  </persistence-unit>
</persistence>

The persistence unit in Listing 5 is pretty much the simplest possible: It uses the default JBoss5 database and re-creates the schema on each run of the program. All the building blocks are now in place. We just need an Ant script to compile, deploy, and run the program.

To compile and deploy the EJB to JBoss5, make sure the application server is running and execute the standard Ant command from the code download folder:

C:\ejbcode>ant

This will compile and deploy the EJB in the JBoss5 deployment folder. Let’s have a quick look at the Ant build script.

The Ant Build Script

As is normal for any Ant script, the file is made up of a set of targets. Each target has a specific purpose, such as compilation, deployment, cleanup, execution, etc. Listing 6 illustrates what is perhaps the most interesting target: Deployment.

Listing 6 The Deployment Target

 <target name="ejbjar" depends="compile">
  <jar jarfile="build/cardsrus.jar">
   <fileset dir="${build.classes.dir}">
      <include name="com/cardsrus/domain/*.class"/>
      <include name="com/cardsrus/cardshop/*.class"/>
   </fileset>
   <fileset dir="${src.resources}/">
     <include name="META-INF/persistence.xml"/>
   </fileset>
   </jar>
   <copy file="build/cardsrus.jar" todir="${jboss.home}/server/default/deploy"/>
 </target>

In Listing 6, the EJB JAR file is created and copied to the server deployment folder. That’s all that’s required to get your code running under JBoss5. If all is well, the deployed EJB JAR is picked up by JBoss and registered. This should result in a flurry of JBoss messages culminating in those illustrated in Listing 7.

Listing 7 Successful Deployment of the EJB

12:32:20,203 INFO [SessionSpecContainer] Starting jboss.j2ee:jar=cardsrus.jar,name=CardShopBean,service=EJB3
12:32:20,437 INFO [EJBContainer] STARTED EJB: com.cardsrus.cardshop.CardShopBean ejbName: CardShopBean
12:32:20,890 INFO [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI:

    CardShopBean/remote - EJB3.x Default Remote Business Interface
    CardShopBean/remote-com.cardsrus.cardshop.CardShopRemote - EJB3.x Remote Business Interface

At this point, you’re ready to run the client.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020