conn.getAutoCommit() is true inside tx

2.1.0

What am I doing wrong?

Context ctx = new InitialContext();

UserTransaction tx =
  (UserTransaction)ctx.lookup("java:comp/UserTransaction");
DataSource ds =
  (DataSource)ctx.lookup("java:comp/env/jdbc/metatv");

Connection conn = null;
tx.begin();
try {
  conn = ds.getConnection();
  System.out.println(conn.getAutoCommit()); // prints true ;-(
} finally {
  try { conn.close(); } catch(Throwable whatever) {}
}
tx.rollback();

TIA

-- 
Dimitri