It is possible that we are working with JPA and we need to access the Hibernate API. Or, vice-versa, we work with Hibernate native and we need to create an EntityManagerFactory from the Hibernate configuration.

To obtain a SessionFactory from an EntityManagerFactory, we’ll have to unwrap the first one from the second one.

Listing 7 Obtaining a SessionFactory from an EntityManagerFactory

private static SessionFactory getSessionFactory
(EntityManagerFactory entityManagerFactory) {
return entityManagerFactory.
unwrap(SessionFactory.class);

private static EntityManagerFactory
createEntityManagerFactory() {
Configuration configuration = new
Configuration(); #1
configuration.configure().
addAnnotatedClass(Item.class); #2

Map properties =
new HashMap<>(); #3
Enumeration propertyNames =
configuration.getProperties().
propertyNames(); #4
while (propertyNames.hasMoreElements()) {
String element = (String)
propertyNames.nextElement(); #5
properties.put(element,
configuration.getProperties().
getProperty(element)); #5
}
return Persistence.
createEntityManagerFactory("cscs",
properties); #6
}

• We create a new Hibernate configuration #1, then call the configure method, which adds the content of the default hibernate.cfg.xml file to the configuration.
• We explicitly add Item as annotated class #2.
• We create a new hash map to be filled in with the existing properties #3.
• We get all property names from Hibernate configuration #4, then we add them one by one to the previously created map #5.
• We return a new EntityManagerFactory, providing to it the cscs persistence unit name and the previously created map of properties #6.

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Catalin Tudose
Java and Web Technologies Expert