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Anchortoptop

Enterprise Java Beans has been one of the corner stones in of the J2EE specification. As a J2EE 1.4 certified application server, Apache Geronimo supports EJB's extensively with the help of OpenEJB EJB Container. Although it is possible to use standard Java objects to contain your business logic and business data, using EJBs addresses many of the issues of using simple Java objects, such as scalability, lifecycle life cycle management and state management. In this article, you 'll will see how an initial database application is extended and used for both locally local and remotely reffered referred application clients for an Enterprise Java Beans back end. The application uses inbuilt built-in Apache Derby as the its database. Use this article to learn how to simplify your enterprise application development process.

Banking application has two types of application clients namely "Banking Remote Application" and "Banking Web Application". Each one of these clients demonstrate how to refer Entrprise Enterprise Java Beans in remote and local interfaces respectively. Both of these clients are reffering referring a common business layer which has been implemented with the help of Session and Entity Beans. Stateless Session Beans are acting as the business service interface between business entities and application clients. All the business entities of the application layer are implemented with the CMP & and BMP Entity Beans. Relations between CMP entities are managed as Container Managed Relations.

After reading this article you should be able get the best out of EJB features of Geronimo, such as defining Enterprise Java Beans, managing relations between them and refer EJB's EJBs via different kind of clients.

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• Overview of EJB Features
• Application Overview
• Configuring, Building and Deploying the Sample Application
• Testing of the Sample Application
• Summary

Overview of EJB Features Anchoroverviewoverview

EJB implementation may vary from one vendor to another. Following The following are the main list of features Apache Geronimo supports as a J2EE container.

• Stateful and stateless Session Beans
• BMP (Bean Managed Persistence) Entity Beans
• CMP (Container Managed Persistence) Entity Beans
• Message driven beans (MDBs)
• Interoperability using RMI-IIOP or JAXRPC
• Ability to expose stateless session beans and MDBs as Web Services
• Support for sending and receiving messages via Web Services
• Easy provisioning and hot deployment of EJB and JMX-based Web Services
• Access to EJBs from external CORBA objects

Application Overview Anchorapplicationapplication

As mentioned above the Banking application of this article supports two types of business application clients. Following are the The overview of each client is given below.

1. Banking Remote Application
   A small Swing swing application client which has more of super user capabilities in the banking enviromentenvironment. Only a limited number of banking staff has have access to this application. It allows to view and update the viewing and updating of balance of bank accounts.
2. Banking Web Application
   A This is a Web application that is going to open to the Customers. It enables them to view their bank account information. Additionally, users of this application can view the exchange rates given by the bank. For the sake of simplicity, security features of each application will be ignored eventhough even though it can be achieved very easily in the context of Geronimo context.

Both of these clients are using use a common business service layer. Behind that buisiness business service layer, there are three common business entities appeared that appear in the banking application domain Account, Customer and ExchangeRate. Each Customer can have more than one Account while an Account can only be only owned by one Customer. ExchangeRate represents a rate value given by the bank in relative to a the USD for a particular currency.

Following The following figure gives the overall architecture of the banking application.

Application contents

The Banking application consist consists of the following list of packages and classes.

• org.apache.geronimo.samples.bank.client
  • MainUI - User interface for the Account Balance Modifier.
• org.apache.geronimo.samples.bank.dto
  • AccountDTO - Use to transfer Account entity related data between different application layers.
  • ExchangeRateDTO - Transfer ExchangeRate entity related data between different application layers.
• org.apache.geronimo.samples.bank.ejb
  • AccountBean - CMP Entity Bean, represent account entity related data in the DB.
  • BankManagerFacadeBean - Stateless Session Bean, acting as a service class for different application clients.
  • CustomerBean - CMP Entity Bean, represent represents customer entity related data.
  • ExchangeRateBean - BMP Entity Bean, represent represents exchange rate relative to a USD.
• org.apache.geronimo.samples.bank.util
  • PropertyLoader - Loads configuration properties to the Account Balance Modifier Client.
• org.apache.geronimo.samples.bank.web
  • CustomerServiceServlet - Dispatches web requests of Customer Account Balance Viewer to the service layer.
  • CommonServiceServlet - Dispatches web request requests of Exchange Rate viewing scenario.

Finally, the banking application will be deployed as an EAR to the application server. Overview The overview of the contents structural content of the EAR file is given in the following example.

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First, we will look at how the business service layer of the application has been implemented with the help of EJBs. In this application enviroment environment all the EJBs are using XDoclet to generate their meta information and most of the interfaces. ejb-jar.xml is a such XDoclet generated file which contains standard information about EJBs.their interfaces.

Corresponding openejb-jar.xml defines Geronimo specific features of EJBs. It has both EJB information and their relationships. In addition to that , it gives a link to the database pool of the application. Entity Beans in the apllication application are depending dependent on this pool. Also note that the final part of this file defines a 1-N Container Managed Relation (CMR) between Customer and Account Entity Beans.

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BankPool.xml is a typical database pool configuration file, which will be connected to the BankDB defined in through the inbuilt Derby database. Entity beans of the application refer the defined database via this configuration file.

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geronimo-application.xml and application.xml define the main components of the EAR. Both EJB component and Web archive information are given in this these files as usual. Additionally, these two XML files define Database application scoped database connection pool information with tranql-connector-1.2.rar and BankPool.xml.

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Since Banking Web Application is a part of EAR, the BankManagerFacade Session Bean will be reffered referred as a local interface. Those additional configuration information of EJBs required for the EJB reference can be found in the web.xml.

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Account Balance Modifier Swing Application refer swing application refers the same BankManagerFacade Session bean as a remotely refer EJB. It's configuration information can be found in the bank_client.properties file.

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Always check for the correct network information to run this application client out side of the local computer.

Sample Database

The sample database that is being used to demonstrate this application is inbuilt Derby database. The name of the sample database is BankDB and it consist consists of following three tables, CUSTOMER ,ACCOUNT and EXCHANGE_RATE. The fields for each of these tables are described below.

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The CUSTOMER table stores the data related to the customers and it store .It stores only the identification number and and his/her the name. ACCOUNT table has a unique account number to the for identification. Account type and balance are the other information stored. CUSTID_FK is a foriegn key to the Customer table which is the owner of the Account. EXCHANGE_RATE table has a primary key of RATE_ID for an identification. Each record of EXCHANGE_RATE has CURRENCY name and RATE paid by the bank.

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XDoclet is an open source code generation engine. It enables Attribute-Oriented Programming for java. In short, this means that you can add more significance to your code by adding meta data (attributes) to your java sources. This is done in special JavaDoc tags.
Although XDoclet originated as a tool for creating EJBs, it has evolved into a general-purpose code generation engine. XDoclet consists of a core and a constantly growing number of modules. It is fairly straightforward straight forward to write new modules if there is a need for a new kind of component.
http://xdoclet.sourceforge.net/xdoclet/index.html

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Configuring, Building and Deploying the Sample Application Anchor configureconfigure

Download the bank application from the following link:
Bank

After decompressing the given file, the bank directory is will be created.

Configuring

Configuration of the application consists of creating the database and defining the connection pool to access it.

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After starting Apache Geronimo log in to into the console and follow the given steps to create the BankDB.

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1. Select DB Manager link from the Console Navigation in the left.
2. Give the database name as BankDB and click Create button.
3. Select BankDB to the Use DB field.
4. Open BankDB.sql in the bank/config directory from a text editor.
5. Paste the content BankDB.sql to the SQL Commands text area and press Run SQL button.

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Bank application comes with an Ant script to help users to build from source code. It has to be properly configured before using it to building build from the source code. build.properties file in the config directory has to modify according to your enviroment. Set the correct paths to the xdoclet.home and geronimo.home directories.
Also set the correct network information in the bank_client.properties file, which are is going to reffered by remote application client.

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This build script depends on XDoclet version 1.2.3 and Geronimo 1.1.1. Also make sure to use "/" as you directory separator in Windows environment when you are setting the above properties.

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Building

Use a command prompt to navigate into the bank directory and just give ant command to build. It will create the Bank.ear and bankclient.jar under the bank/releases folder. Also note it will create a lib folder and copy with a list of jar files refered reffered by the client application. Now, you are ready to deploy bank application in to the Geronimo Application server.

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Deploying sample application is pretty straight forward as we are going to use the Geronimo Console.

1. Travel Scroll down to Deploy New from the Console Navigation panel.
2. Load Bank.ear from bank/releases folder in to the Archive input box.
3. Press Install button to deploy application in the server.

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Testing of the Sample Application AnchorSample Application testingtesting

Core business application logic of the banking application is shared between two different clients. Testing of each client will be is given in below.

Banking Web Application

To test the sample web application open a browser and type http://localhost:8080/Bank^{Image Removed}. It will forward you in to the index page of banking application which has direct links to the view customer and exchange rate information. To view the list of account information of each customer, provide a relavant customer id in the DB. Exchange rate page will display list of all currencies in the exchange rate table.
Image Removed Image Added

Banking Remote Application

Banking remote application client can be run providing java -jar bankclient.jar by issuing the ant run-client in a command prompt. Use an existing account number in the database to view it's balance. Modification of account balance can be done by providing a numeric value to the balance field and using the Update button.

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Always consider lib folder inside of releases are a part of this client application.Check your Operating Sytem's security configuration when you are connecting from a remote machine.

Summary Anchorsummarysummary

This article has shown you how to use the EJB features of the Apache Geronimo. It has provided a step-by-step instructions to build an application, deploy and run it to elaborate those features.

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• Apache Geronimo is a J2EE 1.4 Certified application server and it provides all the necessary features to get for Enterprise applications.
• Create and configure Session and Entity Beans (both BMP and CMP).
• Use Container Managed Relations (CMRs) to manage relations between CMP Entity Beans.
• Access defined enterprise level services by different sorts of clients.