The example below demonstrates the Persistence class in action. You will typically execute code like this on application startup, then cache the resulting factory for future use. This bootstrapping code is only necessary in non-EE environments; in an EE environment EntityManagerFactories are typically injected.

// if your persistence.xml file does not contain all settings already, you
// can add vendor settings to a map
Properties props = new Properties();
...

// create the factory defined by the "openjpa" entity-manager entry
EntityManagerFactory emf = Persistence.createEntityManagerFactory("openjpa", props);