Introduction

This article introduces you to IBM® Rational® Application Developer for WebSphere Software Version 7.5, and walks you through building a JPA entity, session bean, and servlet, and then deploying them to IBM® WebSphere® Version 7.0 .

Java™ Platform, Enterprise Edition Version 5.0 (Java™ EE) makes significant changes in creating enterprise applications due to support for the Java™ Persistence API (JPA), and for Enterprise Java™Beans technology (EJB) V3.0 programming model, annotation, and dependency injection.

Prerequisites

This article assumes that you have Rational Application Developer V7.5 installed with at least the WebSphere V7.0 test server.

Sample application

The sample application you are going to create has a JPA entity, a Session bean that calls the JPA, a Servlet which invokes the Session bean and a web page which calls the servlet. The database used in this application is embedded Derby database which comes along with RAD 7.5. The following diagram illustrates the sequence of interactions in the components of the application.

Follow these steps to develop the application:

1. Create a JPA project and entity, and specify mapping
   
   
2. Create an EJB V3.0 Project, and a session bean that uses a JPA Entity
   
   
3. Create a Web V2.5 project, and a servlet that invokes the session bean
   
   
4. Set a data source and run a Web page on WebSphere V7.0
   
   

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Create a JPA project and entity, and specify mapping

In this example, you create a JPA entity in a separate archive (.jar). Note that the Java EE specification allows you to package JPA entities in a Web or EJB project, too. In Rational Application Developer, you can add JPA facets to a Web or EJB project to enable them for JPA entities.

Create a JPA project

1. In the Java EE perspective, select File > New > Other > JPA Project, as shown in Figure 1.

2. Specify the Project name, as shown in Figure 2.

3. You are prompted for switching to JPA perspective, choose No. JPA perspective has views such as JPA Structure and JPA Details, since Annotations view in the Java EE perspective allows similar functionality, switching to JPA perspective is not necessary.

Note that Rational Application Developer creates a project with these files:

• persistence.xml
• orm.xml
• manifest.MF.

The persistence unit name is set to EmployeeJPA.

Create a JPA entity

4. Right click the project and choose New > Entity, as shown in Figure 4.

5. Specify the package name and class name, as shown in Figure 5, and then click Next.

6. Create the entity fields by clicking the Add button in the following page, as shown in Figure 6.

7. In the resulting Entity Fields dialog, select java.lang.String as the Type from the drop-down list, as shown in Figure 7.

8. Click Finish on the wizard, and you will see a class created with getters and setters for the fields, annotation @Entity, and the annotation @Id for the key field, as shown in Listing 1.

import java.io.Serializable;
import java.lang.String;
import javax.persistence.*;

/**
 * Entity implementation class for Entity: Employee
 *
 */
@Entity


public class Employee implements Serializable {

	   
	@Id
	private String EMP_ID;
	private String First_Name;
	private String Last_Name;
	private static final long serialVersionUID = 1L;

	public Employee() {
		super();
	}   
	public String getEMP_ID() {
		return this.EMP_ID;
	}

	public void setEMP_ID(String EMP_ID) {
		this.EMP_ID = EMP_ID;
	}   
	public String getFirst_Name() {
		return this.First_Name;
	}

	public void setFirst_Name(String First_Name) {
		this.First_Name = First_Name;
	}   
	public String getLast_Name() {
		return this.Last_Name;
	}

	public void setLast_Name(String Last_Name) {
		this.Last_Name = Last_Name;
	}
   
}

Map a database

To make sure that the entity class can properly communicate with the database Table, a mapping between the two is required. JPA provides two mechanisms for mapping. One, by annotation, the other by XML(specified in orm.xml). This example uses the annotation mechanism for mapping.

9. From the Data Source Explorer view in the Java EE perspective, choose Derby Sample Connection > Connect, as shown in Figure 8.

10. Examine the Employee table, as shown in Figure 9.

11. Because the schema does not match, you need to fix mappings.

12. In the Annotation view, click the Table node of the entity, Employee, and specify the following, as shown in Figure 10.
    • Table Name: EMPLOYEE
    • Schema : SAMP

13. Click the column node under EMP_ID and map it to the EMPNO column, as shown in Figure 11.

14. Similarly, map First_Name and Last_Name to the appropriate columns.

15. Now, the Java file will look like that shown in Listing 2.

@Entity

@Table(schema="SAMP", name = "EMPLOYEE")
public class Employee implements Serializable {

	   
	@Id
	@Column(name="EMPNO")
	private String EMP_ID;
	@Column(name="FIRSTNME")
	private String First_Name;
	@Column(name="LASTNAME")
	private String Last_Name;

16. The Java Database Connectivity (JDBC) API data source in the persistence.xml needs to be set. Open the file in Enterprise explorer, as shown in Figure 12.

17. Next, specify the data source, as shown in Figure 13 (an actual data source needs to be created: the steps are shown in the last section).

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Create an EJB V3.0 Project, and a session bean that uses a JPA entity

In this section, you will create an EJB project and a session bean.

Create an EJB Project

1. Choose File > New > EJB Project.

2. Specify the Project name, set the EJB Module version as 3.0, and select the EAR Project Name, as shown in Figure 15. For this example, choose the EAR project that was created when you created the JPA project.

3. Right click the EJB project and select Java EE Module Dependencies, and then select EmployeeJPA.jar, as shown in Figure 16. This creates the manifest entry in the EJB project, and also enables the JPA entity classes visible during development.

Create a session bean

4. Right-click the Session Beans node in the Enterprise Explorer and select New > Session Bean, as shown in Figure 17.

5. Specify the Java package and the class name, as shown in Figure 18. In this example, the Local business interface is selected.

6. Click Finish. The EmployeeSession class and EmployeeSessionLocal business interface are created.

Invoking JPA entity

7. Add a method called findEmployee to the session bean class.

EntityManager em;
    
    public Employee findEmployee(String empNo){
    	Employee emp = (Employee) em.find(Employee.class, empNo);
    	return emp;
    } 

8. You need to define a persistence unit to the entity manager variable. Remember that, when JPA project was created, the EmployeeJPA persistent unit was set in the persistence.xml. You can directly annotate it: @PersistenceContext(name="EmployeeJPA") and import javax.persistence.PersistenceContext, or you can select Add annotation in the Annotation view.

9. Select the bean, as shown in Figure 19.

10. Choose the annotation, as shown in Figure 20.

11. Name the persistence unit EmployeeJPA, as shown in Figure 21.

The action not only adds the annotation, but also sets the import correctly.

12. The final class looks like that shown in Listing 4.

package com.ibm.ejb;

import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import com.ibm.entities.Employee;
import javax.persistence.PersistenceContext;

/**
 * Session Bean implementation class EmployeeSession
 */
@Stateless
public class EmployeeSession implements EmployeeSessionLocal {

    /**
     * Default constructor. 
     */
    public EmployeeSession() {
        // TODO Auto-generated constructor stub
    }
    

    @PersistenceContext(unitName="EmployeeJPA")
    EntityManager em;
    
    public Employee findEmployee(String empNo){
    	Employee emp = (Employee) em.find(Employee.class, empNo);
    	return emp;
    }    

}

13. The business interface of the session bean needs to have the signature of the method you just added. You can do this quickly: select the method in the outline view, and then choose Java EE > Promote Methods, as shown in Figure 22.

14. This opens the Promote Methods dialog. Select the findEmployee(string) method, as shown in Figure 23.

The session bean is now ready to be consumed by the client.

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Create a Web V2.5 Project, and a servlet that invokes the session bean

In this section, you will create a Web project and a servlet.

Create a Web Project

1. Choose File > New > Dynamic Web Project, as shown in Figure 24.

2. Specify the Web Project name, select the Dynamic Web Module version as 2.5, and choose the same EAR Project Name as for the JPA and EJB Project, as shown in Figure 25.

3. Select No when prompted to open the Perspective, as shown in Figure 26, Web perspective has tools for advanced web editing which we do not need in this example.

4. Right-click the Web project and select Java EE Module Dependencies from the list on the left, and then select EmployeeEJBClient.jar and EmployeeJPA.jar, as shown in Figure 27.

Create a servlet

5. Choose New > Servlet from the Servlets node in the Enterprise explorer, as shown in Figure 28.

6. Specify the Java package (com.ibm.servlets) and the Class name (EmployeeSearch) for the servlet, as shown in Figure 29.

7. Modify the doGet method, as shown in Listing 5. The method gets employee id from the request object and uses it to pass to the session bean to find the employee information.

@EJB(name="Employee")
private EmployeeSessionLocal employeeSession; 
	
protected void doGet(HttpServletRequest request,
           HttpServletResponse response) throws
            ServletException, IOException {
  String empNo = request.getParameter("empid");
  Employee emp = employeeSession.findEmployee(empNo);
  if(emp  != null ){
    response.getWriter().println(emp.getFirst_Name() + 
    " " + emp.getLast_Name());
  }else{
    response.getWriter().println("Employee with id =" + 
      empNo + "couldn't be found");
  }
}

8. Create an HTML page in the Web Project that has input field for employee id, and a Submit button, as shown in Listing 6.

<body>
   <form action="/EmployeeWeb/EmployeeSearch" method = "get">
   	 <p>
   	   <label>
             Type Employee ID and press Submit <br/>
             <input type = "text" name = "empid"/>
             <input type = "submit" name = "Submit"/>
   	   </label>
   	 </p>
   </form>
</body>

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Set data source and run Web page on WebSphere V7.0

In this section, you will set the data source and run a Web page.

Setting dataSource

1. Right-click the EAR project, EmployeeEAR, and select JavaEE > Open WebSphere Application Server Deployment, as shown in Figure 30.

2. In the JDBC provider section, click Add and select Database type (Derby) and JDBC provider type (Derby JDBC Provider), as shown in 31.

3. Name the provider (DerbyDB) and select the driver and the Class path (IBM\SDP75\runtimes\base_v7\derby\lib\derby.jar), as shown in Figure 32.

4. Now create the data source by clicking Add, as shown in Figure 33.

5. Select Derby JDBC Provider and Version 5.0 data source, and click the Next button, as shown in Figure 34.

6. Specify the data source name and the JNDI name, as shown in Figure 35. Remember to use the same name JNDI name as you used in the persistence.xml JPA.

7. Locate the sample Derby database in your workspace, and enter the path in the databasename property (workspace\EmployeeSample\metadata\plugins\com.ibm.datatools.db2.cloudscape.driver\SAMPLE), as shown in Figure 36.

Run the Web page

8. Right-click in the EmployeeSerach.html and choose Run As > Run on Server, as shown in Figure 37.

9. The EAR is added to the server, as shown in Figure 38.

10. Enter the EmployeeID and press Submit, as shown in Figure 39.

11. The result is displayed on the screen.

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What you have learned

Java EE V5.0 simplifies enterprise application development. This article showed you how to use Java Persistence API, EJB V3.0, and the tools provided in Rational Application Developer V7.5 to build these enterprise artifacts.

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Resources

Learn

• The developerWorks article Developing Web applications with the Java Persistence API and JavaServer Faces, by Tom Mutdosch, demonstrates JPA Web tools in Rational Application Developer v7.5.
  
  
• The developerWorks article Web 2.0 Application Development using JPA, AJAX, and Dojo tools in Rational Application Developer Version 7.5, by Jarett Stein, explains how to create a simple end-to-end Web application using the JPA, AJAX, and Dojo tools available in IBM Rational Application Developer for WebSphere Software Version 7.5.
  
  
• Understand more about JavaServer Faces tooling in Rational Application Developer Version 7.5 by reading this article What's new in JavaServer Faces tooling in Rational Application Developer Version 7.5?.
  
  
• Understand more about how Rational Application Developer Version 7.5 provides solutions to the many challenges that software teams face when tasked to deliver Web and service-oriented applications by reading this article Why Rational Application Developer for WebSphere Software Version 7.5?.
  
  
• Understand more about how the new functionality of the UML Modeler component common to both IBM Rational Software Architect Standard Edition Version 7.5 and IBM Rational Software Architect for WebSphere Software Version 7.5 by reading this article Using the new features of UML Modeler in IBM Rational Software Architect Version 7.5.
  
  
• Discover all about Rational Application Developer V7.5 on the IBM Rational marketing Web site.
  
  
• Learn all about EJB 3.0.
  
  
• Visit the Rational software area on developerWorks for technical resources and best practices for Rational Software Delivery Platform products.
  
  
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Table of contents

• Introduction
• Create a JPA project and entity, and specify mapping
• Create an EJB V3.0 Project, and a session bean that uses a JPA entity
• Create a Web V2.5 Project, and a servlet that invokes the session bean
• Set data source and run Web page on WebSphere V7.0
• What you have learned
• Download
• Resources
• About the author
• Comments

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