The Developer's Resource & Community Site

COM	XML	ASP	Java & Misc.	NEW: VS.NET
International	This Week	Forums	Author Central	Find a Job

Developing Entity Beans

Author: Gopalan Suresh Raj
Date Submitted: January 6th 2000
Level of Difficulty: Advanced
Subjects Covered: Entity Beans
Pre-required Reading: Entity Java beans, Idevresource.com.

To work with any of these samples, you will need the following:

• JDK 1.1.6 or higher (I use JDK 1.1.7B)
• Swing 1.1 or higher for JDK 1.1 (required if you wanna use the HomeBase GUI)
• The HomeBase (Scunthorpe version 0.5.1) - a free EJB Server from ejbhome.iona.com

To work with the EJB Servlet client, you will need:

• JSDK 2.0 or higher

The Steps involved in developing and deploying an Entity Bean are:

• Set up your Data Source to the Database
• Define your Home Interface.
• Define your Remote Interface.
• Develop your EntityBean
• Define a Primary Key class

*** Note : From this point onwards, whatever we do becomes vendor (HomeBase) specific ***

• Define your Deployment Descriptor
• Compile your classes and generate the Container code using the tools provided by the vendor
• Startup your Server

Figure shows what we are trying to ultimately accomplish in these pages here.

1. Set up your Data Source to the Database
The example program requires a database table named CHECKINGS --the DML of which is shown below-- with the following fields:

CREATE TABLE CHECKINGS
	ACCOUNT_NUMBER	Number
	CUSTOMER_NAME	Text
	BALANCE	Currency
			*primary key (ACCOUNT_NUMBER)

2. Define your Home Interface:

3. Define your Remote Interface:

4. Develop your EntityBean

Bank\CheckingsBean.java

package Bank; import java.rmi.*; import javax.ejb.*; import java.util.*; public class CheckingsBean implements EntityBean {     protected EntityContext _entityContext;     public    int           account_number; //ACCOUNT_NUMBER   public    String        customer_name;  //CUSTOMER_NAME   public    double        balance;        //BALANCE     public int getAccountNumber () {     return this.account_number;   }     public String getCustomerName () {     return this.customer_name;   }     public void credit ( double amount ) {     System.out.println ("==============Invoking CheckingsBean::credit");     System.out.println ("==============changing CheckingsBean::balance from " + balance);     if ( amount > 0 ) {       balance += amount;     }     System.out.println(" to " + balance);   }   public void debit ( double amount ) {     System.out.println ("==============Invoking CheckingsBean::debit");     System.out.println ("==============changing CheckingsBean::balance from " + balance);     if ( (amount > 0) && (balance >= amount) ) {       balance -= amount;     }     System.out.println (" to " + balance);   }   public double getBalance () {     System.out.println ("==============Invoking CheckingsBean::getBalance");     System.out.println ("==============CheckingsBean::balance is " + balance);     return this.balance;   }   public CheckingsBean () {     System.out.println ("==============Invoking CheckingsBean::CheckingsBean");     try {       jbInit ();     }     catch (Exception e) {       e.printStackTrace ();       System.out.println ("==============CheckingsBean::CheckingsBean - jbInit failed");     }   }   // Container managed beans return void   public void ejbCreate ( int accountNo, String customer)     throws RemoteException, CreateException {       System.out.println ("==============Invoking 2 parameter CheckingsBean::ejbCreate");     this.account_number = accountNo;     this.customer_name  = customer;     this.balance   = 0d;     System.out.println ("======================================================");     System.out.println ("CheckingsBean::account_number =" + this.account_number);     System.out.println ("CheckingsBean::customer_name =" + this.customer_name);     System.out.println ("CheckingsBean::balance =" + this.balance);     System.out.println ("======================================================");   }   public void ejbPostCreate ( int accountNo, String customer)     throws RemoteException, CreateException {       System.out.println ("======================================================");     System.out.println ("Invoking 2 parameter CheckingsBean::ejbPostCreate");     System.out.println ("CheckingsBean::account_number =" + this.account_number);     System.out.println ("CheckingsBean::customer_name =" + this.customer_name);     System.out.println ("CheckingsBean::balance =" + this.balance);     System.out.println ("======================================================");   }   public void ejbCreate( int accountNo, String customer, double balance)     throws RemoteException, CreateException {       System.out.println ("Invoking 3 parameter CheckingsBean::ejbCreate");     this.account_number = accountNo;     this.customer_name  = customer;     this.balance   = balance;     System.out.println ("======================================================");     System.out.println ("CheckingsBean::account_number =" + this.account_number);     System.out.println ("CheckingsBean::customer_name =" + this.customer_name);     System.out.println ("CheckingsBean::balance =" + this.balance);     System.out.println ("======================================================");   }   public void ejbPostCreate ( int accountNo, String customer, double balance)     throws RemoteException, CreateException {       System.out.println ("======================================================");     System.out.println ("Invoking 3 parameter CheckingsBean::ejbPostCreate");     System.out.println ("CheckingsBean::account_number =" + this.account_number);     System.out.println ("CheckingsBean::customer_name =" + this.customer_name);     System.out.println ("CheckingsBean::balance =" + this.balance);     System.out.println ("======================================================");   }   public void ejbActivate () throws RemoteException {     System.out.println ("==============Invoking CheckingsBean::ejbActivate======");   }   public void ejbLoad () throws RemoteException {     System.out.println ("==============Invoking CheckingsBean::ejbLoad==========");   }   public void ejbPassivate () throws RemoteException {     System.out.println ("==============Invoking CheckingsBean::ejbPassivate=====");   }   public void ejbRemove () throws RemoteException, RemoveException {     System.out.println ("==============Invoking CheckingsBean::ejbRemove========");   }   public void ejbStore () throws RemoteException {     System.out.println ("==============Invoking CheckingsBean::ejbStore=========");   }   public void setEntityContext (EntityContext context) throws RemoteException {     System.out.println ("==============Invoking CheckingsBean::setEntityContext=");     this._entityContext = context;   }   public void unsetEntityContext () throws RemoteException {     System.out.println ("==============Invoking CheckingsBean::unsetEntityContext");     this._entityContext = null;   }   private void jbInit () throws Exception {     System.out.println ("==============Invoking CheckingsBean::jbInit============");   } }

5. Define a Primary Key class

6. Write the Deployment Descriptor for your Server

Note that the deployment descriptor also specifies the properties of a certain Savings Entity Bean and a Teller Session Bean. Don't be surprised. The code for the Savings Entity Bean is included in the zip file and can be downloaded and is very similar to the Checkings Entity Bean. The steps to develop the Teller Session Bean can be seen at the Developing a Session Bean link. I am using two entity beans (Checkings and Savings) to show how workflow between two entity beans can be co-ordinated and managed by a single session bean (Teller) that creates and manages the entity beans.

7. Compile your classes and generate the Container code using the tools provided by the vendor

8. Startup your Server

The Server is now up and ready and is waiting for connections from the client.

Next part....Developing Session Beans

What do you think of this article?

Have your say about the article. You can make your point about the article by mailing [email protected] (If you haven't allready joined, you can join by going to https://www.onelist.com/community/dev-java).

You can also write a review. We will publish the best ones here on this article. Send your review to [email protected]. Please include the title of the article you are reviewing.

Further Reading

The Enterprise JavaBeans Series:

Enterprise Java Beans By Gopalan Suresh Raj.
In this introduction to Enterprise Java Beans, Gopalan covers the bases then goes on to demonstrate how to build server side business object components. This article is the introduction to Gopalans series of Enterprise JavaBeans articles. (This series of articles is courtesy of Gopalan Suresh Raj)
Author: Gopalan Suresh Raj
Date Submitted: January 6th 2000
Level of Difficulty: Advanced
Subjects Covered: Enterprise JavaBeans, EJB Server, EJB Architecture, Java Naming and Directory Interface, Java Transaction Service.
Pre-required Reading: None

Enterprise Java Beans Series - Components at the Server By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Server side components, CORBA
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Model By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Enterprise JavaBeans, EJB Server, EJB Containers, EJB Clients.
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Naming Services and JNDI By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Naming Services, Java Naming Directory Interface
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Transactions and JTS By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Java Transaction Service, Two-phase commits
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Lifecycle By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: EJB server provider, EJB container provider, EJB developer, EJB deployer, Application developer.
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Servers By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Server Infrastructure
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Containers By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: EJB Containers, EJB Servers
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Components By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: EJB Object, Home Object, Remote Object
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Session Beans By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Stateful Session Beans, Stateless Session Beans
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - EJB Entity Beans By Gopalan Suresh Raj.
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Container-Managed Persistence, Bean-Managed Persistence
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - Writing a Session Bean By Gopalan Suresh Raj.
Part 2 of a four part series: A four tier bank account example
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Developing Session Beans, Home & Remote Interfaces, Deployment Descriptors.
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - Writing an EJB Client By Gopalan Suresh Raj.
Part 3 of a four part series: A four tier bank account example
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: EJB Clients.
Pre-required Reading: Enterprise JavaBeans

Enterprise Java Beans Series - Writing an EJB Servlet Client By Gopalan Suresh Raj.
Part 4 of a four part series: A four tier bank account example
Author: Gopalan Suresh Raj
Date Submitted: January 11th 2000
Level of Difficulty: Advanced
Subjects Covered: Servlet Clients.
Pre-required Reading: Enterprise JavaBeans

Author: Gopalan Suresh Raj

Gopalan has his own site at Author Central (visit him. He also maintains his own site at https://www.execpc.com/~gopalan/) - Contribute to iDevResource.com and you can have one too!

© Copyright 1997-2000 Gopalan Suresh Raj. Reproduced with Permission