code: public int mergeData(Object objData)
      {
          int iErrorCode = DBConstants.NORMAL_RETURN;
          FieldListener nextListener = (FieldListener)this.getListener();
          if (nextListener != null)
              iErrorCode = nextListener.doMergeData(objData);
          else
              iErrorCode = this.doMergeData(objData);
          return iErrorCode;
      }
docs: Merge my changed data back into field that I just restored from disk.
  Note: I don't care about enabled listeners since all the listeners should be disabled on merge.
  @param objData The value this field held before I refreshed from disk.
  @return The setData error code.