JPA - Is there a way/method to retrieve Persistence Unit information - jpa

Question

I'd like to find out my data source name in the code. Is there a way of doing that?
I am using eclipselink.
thanks
To be more specific, my aim is to get an jdbc connection object.
I know i can do that thru:
datasource = (DataSource) (new InitialContext()).lookup("my_data_source_name")
connection = dataSource.getConnection();
But I don't want to hard code the data source name in my code.
I also tried
java.sql.Connection connection = em.unwrap(java.sql.Connection.class);
and it always return null.

Answer 1

.unwrap() should be the way to go, as written in EclipseLink wiki.
I also used to get null when calling em.unwrap(java.sql.Connection.class); because it was not inside a transaction. When called like this:
em.getTransaction().begin();
java.sql.Connection conn = em.unwrap(java.sql.Connection.class);
// ...
em.getTransaction().commit();
everything works fine!

Answer 2

java.sql.Connection connection = em.unwrap(java.sql.Connection.class);
Should work, what version are you using? Ensure that a transaction is active.
To get the data source name you should be able to use,
((JNDIConnector)em.unwrap(JpaEntityManager.class).getSession().getLogin().getConnector()).getName();

Answer 3

Here's what I've found helpful:
private DataSource createDataSource() {
ClientDataSource dataSource = new ClientDataSource();
dataSource.setServerName("localhost");
dataSource.setPortNumber(1527);
dataSource.setDatabaseName("sample");
dataSource.setUser("app");
dataSource.setPassword("app");
return dataSource;
}
private EntityManagerFactory getEntityManagerFactory() {
if (emf == null) {
Map properties = new HashMap();
properties
.put(PersistenceUnitProperties.NON_JTA_DATASOURCE,createDataSource());
emf = Persistence.createEntityManagerFactory(PU_NAME, properties);
}
return emf;
}
Can you create your datasource in the code, rather than configure via persistence.xml?