How to inject persistence context to different data source programmatically

Question

In standard EJB 3, when injecting entity manager, persistence unit (which refers to datasource) is hardcoded into annotation: (or alternatively xml file)

@Pe         


        

Answer 1

• Configure required data-sources & persistent-units in persistence.xml.

      PERSISTENCE_PROVIDER
          java:DATA_SOURCE_NAME


 -- other units  

Now at runtime you can build entity-manager for the required persistence-unit. Create separate persistence-units for each data-source.

//---
EntityManagerFactory emf = Persistence.createEntityManagerFactory(persistenceUnitName);
EntityManager em = emf.createEntityManager();
//---

• Else you can also build factory by providing a map of properties like db-url, userName etc.

createEntityManagerFactory(persistenceUnitName,propertiesMap);

This will create and return an EntityManagerFactory for the named persistence unit using the given properties. Therefore you can change the properties at runtime accordingly.