code: public <T> T getSubAttr(String attrName, String dPath, Class<T> clazz) {
          Lock lock = lockForRead();
          try {
              return JacksonUtils.getValue(getAttribute(attrName), dPath, clazz);
          } finally {
              lock.unlock();
          }
      }
docs: Get a sub-attribute using d-path.
  
  @param attrName
  @param dPath
  @param clazz
  @return
  @see DPathUtils