code: public <T> T getDataAttr(String dPath, Class<T> clazz) {
          Lock lock = lockForRead();
          try {
              return DPathUtils.getValue(dataJson, dPath, clazz);
          } finally {
              lock.unlock();
          }
      }
docs: Get a "data"'s sub-attribute using d-path.
  
  @param dPath
  @param clazz
  @return
  @see DPathUtils