JPA Query

[Abhijit Rai]

Hi ,
I am of the view that JPA may be used for standalone applications (i.e. even without a server(web/application)),
dragged along by this belief I ventured along to make an application

I made an entity class :Cabin

  
package com.titan.domain;

import javax.persistence.*;

@Entity
@Table(name="CABIN")
public class Cabin implements java.io.Serializable{
    private int id;
    private String name;
    private int deckLevel;
    private int shipId;
    private int bedCount;

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

    @Column(name="NAME")
    public String getName( ) { return name; }
    public void setName(String str) {name = str; }

    @Column(name="DECK_LEVEL")
    public int getDeckLevel( ) { return deckLevel; }
    public void setDeckLevel(int level) { deckLevel = level; }

    @Column(name="SHIP_ID")
    public int getShipId( ) { return shipId; }
    public void setShipId(int sid) { shipId = sid; }

    @Column(name="BED_COUNT")
    public int getBedCount( ) { return bedCount; }
    public void setBedCount(int bed) { bedCount = bed; }

}

and a client class: StandaloneClient

package standalone;
import javax.persistence.*;

import com.titan.domain.Cabin;

public class StandaloneClient {
   public static void main(String[] args) throws Exception {
      EntityManagerFactory factory =
         Persistence.createEntityManagerFactory("titan");
      EntityManager manager = factory.createEntityManager( );
      try {
         createCabin(manager);
         Cabin cabin_2 = manager.find(Cabin.class, 1);
         System.out.println(cabin_2.getName( ));
         System.out.println(cabin_2.getDeckLevel( ));
         System.out.println(cabin_2.getShipId( ));
         System.out.println(cabin_2.getBedCount( ));
      } finally {
         manager.close( );
         factory.close( );
      }
   }

   public static void createCabin(EntityManager manager) {
      Cabin cabin_1 = new Cabin( );
      cabin_1.setId(1);
      cabin_1.setName("Master Suite");
      cabin_1.setDeckLevel(1);
      cabin_1.setShipId(1);
      cabin_1.setBedCount(3);

      EntityTransaction transaction = manager.getTransaction( );
      transaction.begin( );
      manager.persist(cabin_1);
      transaction.commit( );
   }
}

also I have persistence.xml within META-INF in my classpath

 

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence">
<persistence-unit name="titan" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>com.foo.Greeting</class>
<properties>
<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/javatest"/>
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
<property name="hibernate.connection.password" value="root"/>
<property name="hibernate.connection.username" value="root"/>
<property name="hibernate.hbm2ddl.auto" value="create-drop"/>
</properties>
</persistence-unit>
</persistence>
	

and all I get is a Fat exception :

   
Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named titan
	at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
	at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
	at standalone.StandaloneClient.main(StandaloneClient.java:9)

Is it possible to use JPA the way I want to use it . If yes ,how do we get over this exception( does any one have the postal address for the Persistence provider ) .
Thanks everyone for helping out

[Cameron Wallace McKenzie]

You don't need any of those silly "Servlet Engines" or overrated "Application Servers" to work with JPA. All you need is a persistence provider; that is, someone who knows how to process JPA stuff, and you're good.

Hibernate is probably the most popular JPA implementation framework. Here's a little class that I can annotate with JPA tags, and pass into the Hibernate Session/EntityManager, and have it persist my data to a database:

  
package com.examscam.model;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;

@Entity
public class User {
  private Long id;
  private String password;

  @Id
  @GeneratedValue
  public Long getId() {return id;}
  public void setId(Long id) {this.id = id;}
  public String getPassword() {return password;}
  public void setPassword(String password) {
    this.password = password;
  }
  public static void main(String args[]){
    AnnotationConfiguration config = 
                     new AnnotationConfiguration();
    config.addAnnotatedClass(User.class);
    config.configure();
    // new SchemaExport(config).create(true, true);
    SessionFactory factory = 
                  config.buildSessionFactory();
    Session session = factory.getCurrentSession();
    session.beginTransaction();
    System.out.println("creating user");
    
    User u = new User();
    u.setPassword("abc123");
    session.saveOrUpdate(u);
    System.out.println("user saved");
    session.getTransaction().commit();
    System.out.println("transaction successful!!!");  
  }
}
  

As you can see, that's all done in a main method - that is, it's done in a standalone Java application that runs on nothing more than a Java 5 JRE. No EJB or Servlet containers are harmed in the running of this code.

Here's a little tutorial in which I detail how to set up this particular configuration with Hibernate and run the code. There's nothing to it, actually:
Using the Java Persistence API (JPA) in a Stand-Alone Java Application (no containers!)

So, in summary, you do not need a J2EE / JEE5 container in order to work with the Java Persistence API.

Regards,

-Cameron McKenzie

[Abhijit Rai]

Hey Cameron,
Thanks mate ,awesome reply ,was like a beautiful sun ray tearing the dark clouds away .
The link was quite useful too . Just as you did I added a main method in my Cabin class and it works like a charm .

  public static void main(String args[]){
	    AnnotationConfiguration config = 
	                     new AnnotationConfiguration();
	    config.addAnnotatedClass(Cabin.class);
	    config.configure();
	    SessionFactory factory = 
	                  config.buildSessionFactory();
	    Session session = factory.getCurrentSession();
	    session.beginTransaction();
	    
	    Cabin cabin=new Cabin();
	    cabin.setBedCount(12);
	    cabin.setDeckLevel(4);
	    cabin.setId(4);
	    cabin.setName("Nickleback");
	    cabin.setShipId(1209);
	    session.save(cabin);
	    
	    session.getTransaction().commit();
	    System.out.println("transaction successful!!!");  
	  }
  

Also the Hibernate configuration xml looks like :

 
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>
	<session-factory>
		<property name="connection.username">root</property>
		<property name="connection.url">jdbc:mysql://localhost:3306/javatest</property>
		<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
		<property name="myeclipse.connection.profile">
			connection
		</property>
		<property name="connection.password">root</property>
		<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="connection.pool_size">1</property>

		<!-- Enable Hibernate's automatic session context management -->
		<property name="current_session_context_class">thread</property>
		<!-- Echo all executed SQL to stdout -->
		<property name="show_sql">true</property>
		
		
		
	</session-factory>

</hibernate-configuration>

   

Thanks again , Cheers