Currently we use the persistence.xml to map a persistenceUnit to data source. Our application got a requirement:

create a new persistence unit programmatically and map it to a new datasource without redeploy or server restart. How to achieve this functionality?

EntityManagerFactory emf = Persistence.createEntityManagerFactory("manager1");
//or
Map configOverrides = new HashMap();
configOverrides.put("hibernate.hbm2ddl.auto", "create-drop");
EntityManagerFactory programmaticEmf =
Persistence.createEntityManagerFactory("manager1", configOverrides);

But the persistence unit "manager1" needs to be defined in persistence.xml.

What we need is:

EntityManagerFactory emf = Persistence.createEntityManagerFactory("foo", "dataSourceName");
the persistence unit "foo" is not defined in any persistence.xml.