Spring: HibernateTransactionManager handling multiple datasources

The Question:

I just spent the past day dealing with this exact question: Why do transactions across data sources appear to work with one hibernate transaction manager?

Like you, I also read in multiple places that I needed to use a JtaTransactionManager...and it turns out they were right! I'll explain:

Configuration:

Just like you, I started with 2 data sources, 2 session factories, and 1 HibernateTransactionManager.

My test code also looked very similar to yours and I could save objects to both databases successfully. If I manually threw an exception, neither save would appear in the database. So it seemed that both were being rolled back correctly. However, when I turned on hibernate's debug logging, I could see that neither save was actually sent to the databases so there was nothing to rollback.

The problem is in the test, so I'll change your test to prove that the single transaction manager is actually not working!

The change we need was suggested by JB Nizet on Jan 2:

Have you tried calling flush on both sessions before throwing the exception?

A better test:

First, add a flush function to each of your DAO's. This is what mine looks like:

public void flush() {    sessionFactory.getCurrentSession().flush();}

Yours will probably look like this:

public void flush() {    getHibernateTemplate().flush();}

Now, modify your test to flush each dao before the exception:

 @Transactional("txManager")public class DaoHolder {    @Transactional(value="txManager", readOnly=false, propagation=Propagation.REQUIRES_NEW, rollbackFor={Exception.class})    private void runTransactionalMethod() throws Exception {        dao1.insertRow();        dao2.insertRow();        dao1.flush();        dao2.flush();        throw new Exception();    }    //...}

The result:

Only the datasource associated to txManager is rolled back. That makes sense, because txManager does not know about the other data source.

Summary:

In my case, I do not need to access 2 databases in one transaction, separate transactions is fine. So I simply defined a second transaction manager:

<bean id="txManager2" class="org.springframework.orm.hibernate3.HibernateTransactionManager">    <property name="sessionFactory" ref="sessionFactory2"/></bean>

And referenced this by name in the Transactional annotation wherever I access the second database:

@Transactional(value="txManager2"...)

I can now get annotated transactions for my second database, but I still cannot get transactions across both databases...it seems that you will need a JtaTransactionManager for that.