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, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.lib.server;
020
021/**
022 * Service interface for components to be managed by the {@link Server} class.
023 */
024public interface Service {
025
026  /**
027   * Initializes the service. This method is called once, when the
028   * {@link Server} owning the service is being initialized.
029   *
030   * @param server the server initializing the service, give access to the
031   * server context.
032   *
033   * @throws ServiceException thrown if the service could not be initialized.
034   */
035  public void init(Server server) throws ServiceException;
036
037  /**
038   * Post initializes the service. This method is called by the
039   * {@link Server} after all services of the server have been initialized.
040   *
041   * @throws ServiceException thrown if the service could not be
042   * post-initialized.
043   */
044  public void postInit() throws ServiceException;
045
046  /**
047   * Destroy the services.  This method is called once, when the
048   * {@link Server} owning the service is being destroyed.
049   */
050  public void destroy();
051
052  /**
053   * Returns the service dependencies of this service. The service will be
054   * instantiated only if all the service dependencies are already initialized.
055   *
056   * @return the service dependencies.
057   */
058  public Class[] getServiceDependencies();
059
060  /**
061   * Returns the interface implemented by this service. This interface is used
062   * the {@link Server} when the {@link Server#get(Class)} method is used to
063   * retrieve a service.
064   *
065   * @return the interface that identifies the service.
066   */
067  public Class getInterface();
068
069  /**
070   * Notification callback when the server changes its status.
071   *
072   * @param oldStatus old server status.
073   * @param newStatus new server status.
074   *
075   * @throws ServiceException thrown if the service could not process the status change.
076   */
077  public void serverStatusChange(Server.Status oldStatus, Server.Status newStatus) throws ServiceException;
078
079}