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Using some of EJB 3.0 functionalities Sample applications Very simple Session EJB example

The Phone Book Bean Example

This is an example of a JSP-page calling an Enity Bean that uses annotations. The result looks like this:

Application Contents

First, let us take a look at the PhoneBook Entity Bean that represents a table in the database. Each instance of PhoneBook is a record of the table.
PhoneBook.java uses the

  1. @Entity annotation to mark this class as an Entity Bean
  2. @Table annotation to map the table name that is being represented by the Entity Bean.
  3. @Id annotation to specify the primary key of the table.

And, as usual their is an empty constructor for the Entity Bean

PhoneBook.java
package org.apache.geronimo.samples.myphonebookpak;

import java.io.Serializable;

import javax.persistence.Id;
import javax.persistence.Entity;
import javax.persistence.Table;

@Entity
@Table(name = "phonebook")
public class PhoneBook implements Serializable {

	private String number;
	private String name;

	public PhoneBook() {

	}

	public PhoneBook(String name, String number) {
		this.name = name;
		this.number = number;
	}

	@Id
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getNumber() {
		return number;
	}

	public void setNumber(String number) {
		this.number = number;
	}
}

MyPhonebookLocal.java is the business interface that drives the above mentioned Entity Bean.

MyPhonebookLocal.java
package org.apache.geronimo.samples.myphonebookpak;

import org.apache.geronimo.samples.myphonebookpak.PhoneBook;

public interface MyPhonebookLocal {
	public PhoneBook findByPrimaryKey(String name);
}

MyPhonebookBean.java is where the implementation of the local (and if there is, a the remote) interface. To explain what the annotations in this Stateless Session Bean means I will enumerate them:

  1. @Stateless - tells Geronimo that this is a stateless session bean
  2. @PersistenceUnit - tells Geronimo to retrieve a persistence unit defined in the persistence.xml and place it in the EntityManagerFactory

    Note that PersistenceContext is used when you are directly obtaining a EntityManager. For an EntityManagerFactory use PersistenceUnit.

MyPhonebookBean.java
package org.apache.geronimo.samples.myphonebookpak;

import javax.ejb.Stateless;
import javax.persistence.PersistenceUnit;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;

import org.apache.geronimo.samples.myphonebookpak.PhoneBook;

@Stateless
public class MyPhonebookBean implements MyPhonebookLocal {

	@PersistenceUnit(unitName="PhonePU")
	protected EntityManagerFactory emf;

	public MyPhonebookBean() {

	}
   
	public PhoneBook findByPrimaryKey(String name) {
		EntityManager em = emf.createEntityManager();

		PhoneBook phonebook = (PhoneBook)em.find(PhoneBook.class, name);

		em.close();

		return phonebook;
	}
}

index.jsp is the JSP page that uses the EJB to access the database.

index.jsp
<%@ page contentType="text/html" import="org.apache.geronimo.samples.myphonebookpak.*, javax.naming.* " %>

<%
	String searchName = "";
	if (request.getParameter("searchname") != null) {
		searchName=request.getParameter("searchname");
	}
%>

<html><head><title>Phonebook</title></head><body>
<form action="index.jsp">
<b>Search number</b>:<br>
Enter name: <input type="text" name="searchname" value="<%=searchName%>">  
<input type="submit" value="Search">
(Test with <a href="index.jsp?searchname=Mattias">Mattias</a>)
</form>
<%
	if (! searchName.equals("")) {
		String number="";
		try {
			Context context = new InitialContext();
			MyPhonebookLocal myPhonebookLocal = (MyPhonebookLocal)context.lookup("java:comp/env/ejb/MyPhonebookBean");
			PhoneBook phonebook = myPhonebookLocal.findByPrimaryKey(searchName);
			if(phonebook != null) {
				number =  phonebook.getNumber();
			}	
		}
		catch (Exception e) {
			number=e.toString();
		}
		out.println("This is the number returned from the EJB when searching for '"+searchName+"' : " + number);
	}
%>
</body></html>

Deployment Plans for EJB

openejb-jar.xml just specifies the module's information.

openejb-jar.xml
<?xml version="1.0" encoding="UTF-8"?>
<openejb-jar
		xmlns="http://www.openejb.org/xml/ns/openejb-jar-2.1" 
		xmlns:nam="http://geronimo.apache.org/xml/ns/naming-1.1" 
		xmlns:pkgen="http://www.openejb.org/xml/ns/pkgen-2.0" 
		xmlns:sec="http://geronimo.apache.org/xml/ns/security-1.1" 
		xmlns:sys="http://geronimo.apache.org/xml/ns/deployment-1.2">
	<sys:environment>
		<sys:moduleId>
			<sys:groupId>org.apache.geronimo.samples</sys:groupId>
			<sys:artifactId>MyPhonebookBean</sys:artifactId>
			<sys:version>1.0</sys:version>
			<sys:type>car</sys:type>
		</sys:moduleId>
	</sys:environment>
</openejb-jar>

persistence.xml will specify the name of the PersistenceUnit. This name is used when referencing for the EntityManagerFactory. I have denoted it as PhonePU. For some reason I could not get it to reference with jta-data-source. So the alternative method is to explicitly specify the ConnectionURL, ConnectionDriverName, and ConnectionUserName. I added an extra property called SynchronizeMappings so that the data in the database will not be overwritten.

persistence.xml
<?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" version="1.0"
		xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
	<persistence-unit name="PhonePU">
		<description>Phone Book</description>
		<provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>
		<class>org.apache.geronimo.samples.myphonebookpak.PhoneBook</class>
		<properties>
			<property name="openjpa.ConnectionURL" value="jdbc:derby:PhoneBookDB" />
			<property name="openjpa.ConnectionDriverName" value="org.apache.derby.jdbc.EmbeddedDriver" />
			<property name="ConnectionUserName" value="app" />
			<property name="openjpa.jdbc.SynchronizeMappings" value="false" />
		</properties>
	</persistence-unit>
	<!--
	<jta-data-source>PhoneBookPool</jta-data-source>
	<non-jta-data-source>PhoneBookPool</non-jta-data-source>
	-->
</persistence>
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