Spring Transaction propagation nested Propagation REQUIRES_NEW in Propagation.REQUIRED - spring

Question

I'm using Spring 3.2 integrate with hibernate 4
Here is my code
#Service
public class MyService{
#AutoWired
private NestedServcie ns;
#Transactional(propagation=Propagation.REQUIRED)
public void outer(){
while(true){
dao.findOne(); // This method find data from db using hibernate hql
ns.inner(); // insert some data and commit and loop again.
}
}
}
#Service
public class NestedServcie{
#Transactional(propagation=Propagation.REQUIRES_NEW)
public void inner(){
//here insert some data into db using hibernate
}
}
Here is the spring config xml
<tx:annotation-driven transaction-manager="transactionManager"/>
<bean id="transactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory"/>
</bean>
And here is my question
before I run this program, there is no data in db, so dao.findOne() is null in the first loop. But after ns.inner() excute, I insert some data into db and commit (where I think REQUIRES_NEW works). And when the second loop begin, dao.findOne is still null, the outer
can not get the inner insert data. why??
Thanks!!

Answer 1

There is already an ongoing transaction which basically has its own version of the data. The newly added data is not visible to that transaction. Next to that you have hibernate in the mix, which uses caching and depending on what is executed, the query is only executed once and on subsequent calls it simply returns the cached values (within the same transaction/session for instance).
Links
Can/Should spring reuse hibernate session for sub transaction
Transaction Isolation
Visibility of objects in different hibernate sessions