How do I connect to multiple databases using JPA?

Question

I have an application using Java servlets/JSP\'s. There are multiple clients using my app, however each client has a separate database. All the databases have the same schem

Answer 1

1) Create several persistent units in your persistence.xml with different names.

2) Create necessary number of EntityManagerFactorys (1 per persistence-unit) and specify which persistence-unit should be used for concrete factory:

3) Create necessary number of TransactionManager s:

4) In your DAO's classes specify with which persistence-unit (and so with which EntityManagerFactory) you want to work:

public class AbstractAuthDao { 

   @PersistenceContext (unitName = "SpringSecurityManager")
   protected EntityManager em;

    ...
}

5) In your service-objects specify which TransactionManager should be used (this feature is supported only in Spring 3.0):

@Transactional (value = "authTransactionManager", readOnly = true)
public class UserServiceImpl implements UserService {

   ...
}

6) If you have OpenEntityManagerInViewFilter in your web.xml, then specify in its init-param name of necessary EntityManagerFactory (or create several filters with correspondent init-blocks):

    entityManagerFactoryBeanName
    authEntityManagerFactory