code: public void setListeners(Listener[] listeners) {
          if (listeners != null && listeners.length > 0
                  && this.listeners != null && this.listeners.length > 0) {
              Listener[] oldListeners = this.listeners;
              this.listeners = new Listener[oldListeners.length + listeners.length];
              System.arraycopy(oldListeners, 0, this.listeners, 0, oldListeners.length);
              System.arraycopy(listeners, 0, this.listeners, oldListeners.length, listeners.length);
          } else {
              this.listeners = listeners;
          }
      }
docs: httl.properties: listeners=httl.spi.listeners.ExtendsListener