Hibernate Transactions with Annotations

The current session is maintained in the SessionFactory throughout the call if it has the @Transactional annotation.

Here are the steps for setting the Transactions

Pass the sessionFactory to the transactionManager.

<bean id="transactionManager"
class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>

Add the tx namespace to context.xml

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">

.
.
.

<tx:annotation-driven />

Place the annotations above the methods you are going to use the sessionFactory.

@Transactional
public Product getProductById(final long id) {
final Session session = sessionFactory.getCurrentSession();
final Product product = (Product) session.get(Product.class, id);
return product;
}

Here are some points to remember:
1. If you want a method to be transactional.
2. The classes that use transactional annotation should use not use constructor autowire. - It will give bean creation exceptions. I have used setter injection autowire byType.
3. If a class is calling a method that needs transaction, The public method needs to be transactional. So you cannot call from outside, a non-transactional public method and then delegate to a transactional method.
4. How do you check if the hibernate transactions are working?
Insert in the method : sessionFactory.getCurrentSession()
If the transactions are not set correctly, you will get errors.
5. If the transaction is going to run a batch job, flush and clear the session at batches of 20 - 30.

final Session session = sessionFactory.getCurrentSession();
int count = 0;
for (final EipCharge charge : eipCharges) {
// Do the stuff .....
.....
if (count % 20 == 0) {
session.flush();
session.clear();
}
count++;
}