content: /*
   * Latke - 一款以 JSON 为主的 Java Web 框架
   * Copyright (c) 2009-present, b3log.org
   *
   * Latke is licensed under Mulan PSL v2.
   * You can use this software according to the terms and conditions of the Mulan PSL v2.
   * You may obtain a copy of Mulan PSL v2 at:
   *         http://license.coscl.org.cn/MulanPSL2
   * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
   * See the Mulan PSL v2 for more details.
   */
  package org.b3log.latke.event;
  
  import org.apache.logging.log4j.Level;
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  /**
   * Abstract event listener (Observer).
   *
   * @param <T> the type of event data
   * @author <a href="http://88250.b3log.org">Liang Ding</a>
   * @version 1.1.0.6, Oct 31, 2018
   */
  public abstract class AbstractEventListener<T> {
  
      /**
       * Logger.
       */
      private static final Logger LOGGER = LogManager.getLogger(AbstractEventListener.class);
  
      /**
       * Gets the event type of this listener could handle.
       *
       * @return event type
       */
      public abstract String getEventType();
  
      /**
       * Performs the listener {@code action} method with the specified event
       * queue and event.
       *
       * @param eventQueue the specified event
       * @param event      the specified event
       * @see #action(org.b3log.latke.event.Event)
       */
      final void performAction(final AbstractEventQueue eventQueue, final Event<?> event) {
          final Event<T> eventObject = (Event<T>) event;
  
          try {
              action(eventObject);
          } catch (final Exception e) {
              LOGGER.log(Level.WARN, "Event perform failed", e);
          } finally { // remove event from event queue
              if (eventQueue instanceof SynchronizedEventQueue) {
                  final SynchronizedEventQueue synchronizedEventQueue = (SynchronizedEventQueue) eventQueue;
  
                  synchronizedEventQueue.removeEvent(eventObject);
              }
          }
      }
  
      /**
       * Processes the specified event.
       *
       * @param event the specified event
       */
      public abstract void action(final Event<T> event);
  }
  