code: @Override
      public String getMessageSelector() throws JMSException {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "getMessageSelector");
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "getMessageSelector", theSelector);
  
          //if selector is null or empty return null
          if (theSelector == null || theSelector.trim().isEmpty())
              return null;
  
          return theSelector;
      }
docs: /*
  (non-Javadoc)
  
  @see javax.jms.QueueBrowser#getMessageSelector()