code: @Override
      public void customize(Session session) throws Exception {
          JNDIConnector connector;
          // Initialize session customizer
          DataSource dataSource;
          try {
              Context context = new InitialContext();
              if (null == context) {
                  throw new VMException("Context is null");
              }
              connector = (JNDIConnector) session.getLogin().getConnector(); // possible CCE
              // Lookup this new dataSource
              dataSource = (DataSource) context.lookup(JNDI_DATASOURCE_NAME);
              connector.setDataSource(dataSource);
              // Change from COMPOSITE_NAME_LOOKUP to STRING_LOOKUP
              // Note: if both jta and non-jta elements exist this will only change the first one - and may still result in the COMPOSITE_NAME_LOOKUP being set
              // Make sure only jta-data-source is in persistence.xml with no non-jta-data-source property set
              connector.setLookupType(JNDIConnector.STRING_LOOKUP);
  
              // if you are specifying both JTA and non-JTA in your persistence.xml then set both connectors to be safe
              JNDIConnector writeConnector
                      = (JNDIConnector) session.getLogin().getConnector();
              writeConnector.setLookupType(JNDIConnector.STRING_LOOKUP);
              JNDIConnector readConnector
                      = (JNDIConnector) ((DatabaseLogin) ((ServerSession) session)
                              .getReadConnectionPool().getLogin()).getConnector();
              readConnector.setLookupType(JNDIConnector.STRING_LOOKUP);
  
              // Set the new connection on the session
              session.getLogin().setConnector(connector);
          }
          catch (Exception e) {
              LOG.log(Level.SEVERE, JNDI_DATASOURCE_NAME, e);
          }
      }
docs: Get a dataSource connection and set it on the session with
  lookupType=STRING_LOOKUP
  
  @param session Session
  @throws java.lang.Exception If an error occurs.