public static RelaDataManager buildRelaDataManager() {
if(relaDataManager == null) {
synchronized (RelaDataManagerBuilder.class) {
if(relaDataManager == null) {
Configuration configuration = Configuration.getInstance();
String type = configuration.getProperty(RELA_DATA_MANAGER_TYPE);
if("datasource".equals(type))
relaDataManager = new DataSourceRelaDataManager();
else if("nosql".equals(type))
relaDataManager = new NoSqlRelaDataManager();