dataevent.java

自己写的一个聊天的小程序 请多多指教

/*
 * Copyright (c) 2003 - 2007, Silvio Meier and Tobias Reinhard
 *
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, 
 * with or without modification, are permitted provided 
 * that the following conditions are met:
 *
 *   o Redistributions of source code must retain the above 
 *     copyright notice, this list of conditions and the 
 *     following disclaimer.
 *   o Redistributions in binary form must reproduce the above 
 *     copyright notice, this list of conditions and the 
 *     following disclaimer in the documentation and/or other 
 *     materials provided with the distribution.
 *   o The names of its contributors may not be used to endorse 
 *     or promote products derived from this software without 
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package net.sf.cscc;
import java.io.Serializable;

/**
 *  This class encapsulates the data which is associated with a specific
 *  data event that occurred.
 *
 *	@author			Silvio Meier (SM)
 *	@copyright      Silvio Meier, Tobias Reinhard, 2003
 *	@history		2003-05-09 SM First Version
 *                  2003-05-14 SM working on additional methods and events,
 *                                correction of some comments.
 *                  2003-05-21 SM Added methods for retrieving the client id
 *                                if the data event was received by a server.
 *                  2006-11-02 SM Comments revised.
 *	@version		$Date: 2007/07/01 17:04:05 $, $Author: reode_orm $, $Revision: 1.1 $
 *	@obligation		Objects which are encapsulated by this class have to
 *                  implement the {@link java.io.Serializable} interface. Also
 *                  all objects which are reachable (intransiently referenced)
 *                  in the object reference graph from the
 *                  encapsulated object have to implement the
 *                  {@link java.io.Serializable} interface.
 */
public class DataEvent implements Serializable {

    /**
	 * Serial id for serialization.
	 */
	private static final long serialVersionUID = -5265956446620156753L;

	/**
     *  This variable stores a key which identifies the event uniquely.
     *  This key can be any object and helps the user to determine which
     *  kind of data is encapsulated in this DataEvent object.
     */
    protected Object eventKey;

    /**
     *   This field refers to the data which is encapsulated in this DataEvent.
     */
    protected Object data;

    /**
     *  This variable refers to the object identifying the sender client uniquely.
     */
    protected Object clientId;

    /**
     *   Constructor initializes the object.
     *
     *   @pre key != null && data != null
     *   @post true
     *   @param key Key which identifies the type of the event which occurred.
     *          The content of this key can be used to determine which type
     *          of data is transmitted
     *   @param data The data which should be transmitted. The class of this
     *          object must implement the interface {@link java.io.Serializable}.
     *          All of the directly or indirectly intransiently referenced
     *          data objects must implement this interface.
     */
    public DataEvent(Object key, Object data) {
        eventKey = key;
        this.data = data;
        this.clientId = null;
    }

    /**
     *   This method returns the encapsulated event data. The type of the
     *   object can be determined by using the event key. This is done by
     *   calling the method {@link #getEventKey()}.
     *   @pre true
     *   @post true
     *   @return Returns the object containing the data which is associated
     *           with the occurring event.
     */
    public  Object getData() {
        return data;
    }

    /**
     *   This method returns the event key. The event key information
     *   can be used to determine which kind of data is encapsulated within
     *   this object.
     *
     *   @pre true
     *   @post true
     *   @return Returns the event key of this event.
     */
    public  Object getEventKey() {
        return eventKey;
    }

    /**
     *  This method sets the id for identifying the client. This method will
     *  be used internally by the server.
     *  @pre  id != null
     *  @post true
     *  @param id Identification object for the client.
     */
    void setClientId(Object id) {
        this.clientId = id;
    }

    /**
     *  This method returns the client id which is represented as an object.
     *  The sender client Id is set if the DataEvent object is received
     *  at a target client.
     *  This id object is used to identify from which client this DataEvent
     *  was sent. If  the data event is received by the server, <i>null</i>
     *  is returned.
     *
     *  @pre   true
     *  @post  true
     *  @return Returns the client id as object, if this DataEvent object is
     *          received by the server.
     */
    public Object getClientId() {
        return this.clientId;
    }
}