public QueryManager getQueryManager() { if (qm == null) { synchronized (this) { if (qm == null) { try { String pluginClass = CommonProperties.getInstance().getProperty(QUERY_MANAGER_CLASS_PROPERTY); qm = (QueryManager) createPluginInstance(pluginClass); } catch (Exception e) { String errmsg = "[QueryManager] Cannot instantiate " + "QueryManager plugin. Please check that " + "property '" + QUERY_MANAGER_CLASS_PROPERTY + "' is correctly set in omar-common.properties file."; log.error(errmsg, e); } } } } return qm; }