Using Spring, JPA with Hibernate to access multiple databases/datasources configured in Jboss

Question

I have a requirement where i need to configure a Spring based application to work with two databases. We have two databases, one that we use to keep the live data and the other

Answer 1

Spring has exactly what you want - the AbstractRoutingDataSource. See this blog post on how to use it. In your case, you need to switch the datasource during one request, so you'll need to have 2 transactions, switching the datasource between them by changing the datasource indicator on the ThreadLocal:

1. For these DAOs, demarcate the wrapping Service-layer either with distinct packages, class names, or method names
2. Indicate to Spring that the Service-layer method calls should run in their own transactional contexts by annotating with @Transactional(propogation=Propogation.REQUIRES_NEW)
3. Create an Aspect (using AspectJ annotation @Aspect) to fire around the service-layer method calls (using @Around) to set the ThreadLocal value before the method call, and to unset it afterwards
4. In the @Controller, simply call the Service-layer methods. The Aspect will take care of setting the values to indicate which datasource to use, and the AbstractRoutingDataSource will use that datasource in the context of each transaction.