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Spring Hibernate Example:
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Written By : Amit
Title :
Interview Questions

Description :
On Hibernate
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Written By : Amit
Title :
mapping class hierarchy table per subclass

Description :
Example
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Written By : Amit
Title :
ways create Hibernate SessionFactory

Description :
Example
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Written By : Amit
Title :
Spring Hibernate Integration example

Description :
Example
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Written By : Amit
Title :
ORM Hibernate Best FIT

Description :
Discussion
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Written By : Amit
Title :
One to Many mapping example

Description :
Code
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Tags/Keywords : Spring Hibernate Example, Spring, Hibernate, Example, Code, Tutorial, Article
Author : Amit
Date (Year/Month/Date): 2009-02-18
SpringFramework and Hibernate Integration an example discussed

Please be informed that NONE of the design/code from this
page is claiming to be some sort of best practices and we DO NOT expect
any of our visitor/reader of this page to assume this as some sort of
best practice for any context and should not be using this 
as it is without appropriate evaluation to their, so to say, 
specific programming context.

This page intends only to provide bit and piece of known ways  for
doing some sort of example and may not be fit for any other purpose.

I have spend many hours in understanding how I think can be
a way of setting up Spring and Hibernate using JBoss
application server, in my small local development environment.



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I have tried my ways and means of arranging for required
software and start this demonstration quickly.

My Software environment for this example:
1. Eclipse 3.2
2. JDK 1.5
3. Hibernate 3.2
4. SpringFramework 1.2.8
5. MySQL database 5.0
6. JBoss 5.0.0 Beta2

Objective of this exercise is to use application server
JTA transaction along with Spring and Hibernate, and EJB.

So idea is to create an EJB session bean, and configuring
Spring and Hibernate to as to be able to use the
Container Managed Transaction initiated by the client requesting
session bean, to Spring BeanFactory to get the Hibernate SessionFactory
created. Using this SessionFactory, and Session, I should be able to
do a simple JDBC insert operation on database table.

In this way JTA transaction actually initiating Session, throughout
the complete lifecycle of Session bean transaction begin and commit
/rollback and this operation is getting automatically rolled back
in case of any exception raised in Database.

Steps I followed are as follows:
1. Created a workspace in Eclipse.
2. Created a Java project.
3. Created a source folder.
4. Now using my prior experience of creating Session bean in JBoss.
   (If anyone interested in learning how to use XDoclet 1.2.3 to
    create JBoss Session Bean EJB3.0 , using annotation, then I shall
	be writing an article on this topic as well. Keep visiting for
	updates)
5. Created a DAO class for hiding all Hibernate SessionFactory and Session
   related operation insulated from the Session Facade.

6. Now, most important part is, defining applicationContext.xml file
   using SpringFramework.

7. My configuration is defined in applicationContext.xml file as follows:
<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"
          "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>
<bean id="myDataSource"
      class="org.springframework.jndi.JndiObjectFactoryBean">
	<property name="jndiName" value="java:/MysqlDS"/>
</bean>
<bean id="mySessionFactory"
      class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
	<property name="dataSource" ref="myDataSource"/>
	<property name="mappingResources">
	<list>
		<value>User.hbm.xml</value>
	</list>
	</property>
 <property name="hibernateProperties">
  <props>
	<prop key="hibernate.dialect">
	    org.hibernate.dialect.MySQL5InnoDBDialect
	</prop>
	<prop key="hibernate.show_sql">true</prop>
	<prop key="hibernate.current_session_context_class">
	  jta
	</prop>
	<prop key="hibernate.transaction.factory_class">
	    org.hibernate.transaction.JTATransactionFactory
	</prop>
	<prop key="hibernate.transaction.manager_lookup_class">
	    org.hibernate.transaction.JBossTransactionManagerLookup
	</prop>
	<prop key="jta.UserTransaction">UserTransaction</prop>
  </props>
 </property>
</bean>
</beans>
 

This applicationContext.xml file is pretty much self explanatory.
First part is the way I defined the DataSource, and the SessionFactory.
SessionFactory has various Hibernate properties for setting up JTA
Transaction, with the help of JBossTransactionManagerLookup
and JTATransactionFactory.

Current session context is defined as "jta", for the Hibernate session
to be initiated during the JTA Transaction startup. And there is no
need for the developer to open and close/flush Hibernate Session in code.
Instead, one has to just use the getCurrentSession for getting the
same session throughout the complete transactional operation.

jta.UserTransaction, is looking up the JNDI UserTransaction of the
application server for using it in JTA.

Now one very important question is:
How to get a handle of Hibernate SessionFactory in EJB code/ DAO?

I have used a Singleton class for looking loading applicationContext.xml
file and getting the SessionFactory as a Bean from the Spring BeanFactory.

This Singleton class is very inserting to see and is as follows:

/**
* This code is provided "AS IS".
*
*/

import javax.transaction.Transaction;

import org.hibernate.SessionFactory;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SessionFactoryProvider
{
	private SessionFactory sessFactory;
	private Transaction userTrans = null;
	private final static SessionFactoryProvider sessFactProvider
                                          = new SessionFactoryProvider();
	private SessionFactoryProvider()
	{
         ClassPathXmlApplicationContext appContext =
			  new ClassPathXmlApplicationContext(
                               new String[] {"applicationContext.xml"});
        BeanFactory factory = (BeanFactory) appContext;
        sessFactory = (SessionFactory)factory.getBean("mySessionFactory");
	}
	public static SessionFactoryProvider getInstance()
	{
		return sessFactProvider;
	}
	public SessionFactory getSessionFactory()
	{
		return this.sessFactory;
	}
}
 

If this Singleton class is loaded for the first time, the it creates
SessionFactory for one time only, and returns SessionFactory, on request
using getSessionFactory().

I have chosen to instantiate Singleton class in ejbCreate lifecycle method
of the Session bean, so as to have the SessionFactory created before any
business method invocation:

	public void ejbCreate() throws CreateException {
		SessionFactoryProvider.getInstance();
    }


Having written all these, I wanted your thinking about a particular
scenario where by I am not being able to execute this code from a WAR
file.

Same applicationContext.xml file when used in a web application and
loaded using context loader listener/Servlet, I was getting a
ClasscastException for the Transaction part while Hibernate SessionFactory
is getting loaded/instantiated.

I think, I am not sure, but it could be due to the JDBCTransaction
getting initiated instead of JTA transaction in Web application
and in WAR file.

Did anybody encountered this kind of exception? do write
your experience to me By Replying to this writing.



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while working with the example code environment setting up, running
and resolving any such exception raised during compile or at runtime.
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from the Author for FREE.

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