private boolean userExists(String name) throws PersistenceException {
    return dataStore != null &&
        dataStore.find(PhoneUser.class, name) != null || viewContext.getInstanceData(name) != null;
  }
The view data store.
<code>null</code> indicates that the view properties should be used instead of the data store.
ambari-views/examples/phone-list-upgrade-view/src/main/java/org/apache/ambari/view/phonelist/PhoneListServlet.java