/*************************************************************************
* Copyright 2009-2012 Eucalyptus Systems, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 3 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see http://www.gnu.org/licenses/.
*
* Please contact Eucalyptus Systems, Inc., 6755 Hollister Ave., Goleta
* CA 93117, USA or visit http://www.eucalyptus.com/licenses/ if you need
* additional information or have any questions.
*
* This file may incorporate work covered under the following copyright
* and permission notice:
*
* Software License Agreement (BSD License)
*
* Copyright (c) 2008, Regents of the University of California
* All rights reserved.
*
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************************************************************************/
package com.eucalyptus.util.async;
import com.eucalyptus.util.Callback;
import edu.ucsb.eucalyptus.msgs.BaseMessage;
/**
* An asynchronous callback which involves remote communication (read: possibly long lasting). Implementors of this interface are guaranteed that:
*
* <ul>
* <li>{@link #initialize(BaseMessage)} will be invoked before communication begins.</li>
* <li>Should the invokation of {@link #initialize(BaseMessage)} terminate prematurely the callback will be disposed of -- preconditions
* caused a failure.</li>
* <li>Otherwise, either {@link #fire(BaseMessage)} <b>OR</b> {@link #fireException(Throwable)} will be called exactly
* one time.</li>
* <li>The argument to {@link #fire(BaseMessage)}/{@link #fireException(Throwable)} will be the outcome of the remote
* operation.</li>
* </ul>
* @see Callback
* @see Callback.Checked
* @see Callback.TwiceChecked
* @see RemoteCallback#fire(BaseMessage)
* @see RemoteCallback#fireException(Throwable)
*/
public interface RemoteCallback<Q extends BaseMessage, R extends BaseMessage> extends Callback.TwiceChecked<Q, R> {
/**
* Get the request being made by this callback.
*/
Q getRequest( );
/**
* Initialize (e.g., check preconditions) before proceeding with the
* connection and sending of <tt>request</tt>. Guaranteed to be called only
* once per corresponding dispatch.
*/
@Override
void initialize( Q request ) throws Exception;
/**
* The operation completed with a response: <tt>msg</tt>.
*/
@Override
void fire( R msg );
/**
* The operation completed with an exception.
*/
@Override
void fireException( Throwable t );
}