code: public void debug(Object m, Throwable ex)
      {
          if (_debugOn)
          {
              Frame frame = new Frame(1,true);
              if (isDebugOnFor(frame))
              {
                  frame.complete();
                  message(DEBUG,new Object[]{m,ex},frame);
              }
          }
      }
docs: /* (non-Javadoc)
  @see org.apache.commons.logging.Log#debug(java.lang.Object, java.lang.Throwable)