Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.wake.impl;
020
021import org.apache.reef.wake.EventHandler;
022import org.apache.reef.wake.exception.WakeRuntimeException;
023
024import java.util.Map;
025
026/**
027 * Event handler that dispatches an event to a specific handler based on an event class type.
028 *
029 * @param <T> type
030 */
031public class MultiEventHandler<T> implements EventHandler<T> {
032
033  private final Map<Class<? extends T>, EventHandler<? extends T>> map;
034
035  /**
036   * Constructs a multi-event handler.
037   *
038   * @param map a map of class types to event handlers
039   */
040  public MultiEventHandler(final Map<Class<? extends T>, EventHandler<? extends T>> map) {
041    this.map = map;
042  }
043
044  /**
045   * Invokes a specific handler for the event class type if it exists.
046   *
047   * @param event an event
048   * @throws WakeRuntimeException
049   */
050  @Override
051  public void onNext(final T event) {
052    final EventHandler<T> handler = (EventHandler<T>) map.get(event.getClass());
053    if (handler == null) {
054      throw new WakeRuntimeException("No event " + event.getClass() + " handler");
055    }
056    handler.onNext(event);
057  }
058
059}
060
061