Spring-boot with JPA Repositories using JTA Transaction Manager using JBOSS 6

First of all - do you really need JTA? Typically spring+hibernate don't require it. You can use a simple JpaTransactionManager / HibernateTransactionManager.

If you really want JTA, then you will need a JTA provider. If not running in an application server, check this question for how to use JTA in a servlet container. (Also take a look at this question)

Finally, hibernate docs specify that, for container-managed transactions:

Declarative transaction demarcation is a standard feature of EJB, also known as container-managed transactions (CMT). In EJB 2.x you would use XML deployment descriptors to create your transaction assembly. In EJB 3.x you can use JDK 5.0 annotation metadata directly in your source code, a much less verbose approach. To enable CMT transaction demarcation for EJBs in Hibernate configuration:

• set hibernate.transaction.manager_lookup_class to a lookup strategy for your JEE container
• set hibernate.transaction.factory_class to org.hibernate.transaction.CMTTransactionFactory

The second point is perhaps something you've missed?

What the documentation says in addition to that (the next section) is that if you want declarative transaction, hibernate is not where you should look at. You'd need to create an interceptor. That's exactly what spring transaction managers are. And that would be my choice given your technology stack (Spring).

If you wish not to rely on a single JTA provider, then make two builds. For example maven has "maven profiles", which allow to make builds for different environments.

Transaction Managers and Websphere:

Websphere does not use the typical jndi standard when supplying the transaction manager. Spring has worked around this by providing the org.springframework.transaction.jta.WebSphereUowTransactionManager that you can use to lookup the websphere transaction manager.

Datasource and Isolation Levels

You typically cannot change the isolation level of a datasource and I know you cannot change it when connecting from websphere to DB2 database (it's set as a parameter on the datasource configuration). The allowCustomIsolationLevels flag lets you select different data sources for different requested isolation levels..

See here and here