core/src/main/java/org/apache/hama/bsp/sync/ZKSyncEventFactory.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hama.bsp.sync;

/**
 * Zookeeper Synchronization Event Factory.
 * <ul>
 * It provides three event definitions.
 * <li>Value stored in a Zookeeper node is changed
 * <li>A new child node is added to a Zookeeper node.
 * <li>A Zookeeper node is deleted.
 * </ul>
 */
public class ZKSyncEventFactory {

  public static enum ZKEvent {
    VALUE_CHANGE_EVENT(0), CHILD_ADD_EVENT(1), DELETE_EVENT(2);

    private final int id;

    ZKEvent(int num) {
      this.id = num;
    }

    public int getValue() {
      return this.id;
    }

    public static int getEventCount() {
      return ZKEvent.values().length;
    }

    public String getName(int num) {
      if (num >= 0 && num < ZKEvent.getEventCount()) {
        return ZKEvent.values()[num].name();
      } else
        throw new IllegalArgumentException(
            (new StringBuilder(100).append("The value ").append(num)
                .append(" is not a valid ZKEvent type. ")
                .append("Expected range is 0-").append(getEventCount() - 1))
                .toString());
    }

  }

  public static int getSupportedEventCount() {
    return ZKEvent.getEventCount();
  }

  private static class ValueChangeEvent implements SyncEvent {

    @Override
    public int getEventId() {
      return ZKEvent.VALUE_CHANGE_EVENT.getValue();
    }

  }

  private static class ChildAddEvent implements SyncEvent {

    @Override
    public int getEventId() {
      return ZKEvent.CHILD_ADD_EVENT.getValue();
    }

  }

  private static class DeleteEvent implements SyncEvent {

    @Override
    public int getEventId() {
      return ZKEvent.DELETE_EVENT.getValue();
    }

  }

  /**
   * Provides the Zookeeper node value change event definition.
   * 
   * @return the Zookeeper value changed event.
   */
  public static SyncEvent getValueChangeEvent() {
    return new ValueChangeEvent();
  }

  /**
   * Provides the Zookeeper deletion event definition.
   * 
   * @return the Zookeeper node is deleted event
   */
  public static SyncEvent getDeletionEvent() {
    return new DeleteEvent();
  }

  /**
   * Provides the Zookeeper child addition event definition.
   * 
   * @return the Zookeeper child node is added event
   */
  public static SyncEvent getChildAddEvent() {
    return new ChildAddEvent();
  }

}