docs: public void registerDataSource(String name, DataSource dataSource) {
          if (dataSource == null) {
              throw new NullPointerException("dataSource");
          }
          if (StringUtils.isBlank(name)) {
              throw new IllegalArgumentException("blank name");
          }
          if (name.equals("*")) {
              defaultDataSource = new DataSourceHolder(dataSource);
          } else {
              dataSources.putIfAbsent(name, new DataSourceHolder(dataSource));
          }
      }