/**************************************************************************************
* Copyright (C) 2008 EsperTech, Inc. All rights reserved. *
* http://esper.codehaus.org *
* http://www.espertech.com *
* ---------------------------------------------------------------------------------- *
* The software in this package is published under the terms of the GPL license *
* a copy of which has been included with this distribution in the license.txt file. *
**************************************************************************************/
package com.espertech.esper.dispatch;
/**
* Service for dispatching internally (for operators/views processing results of prior operators/views) and
* externally (dispatch events to UpdateListener implementations).
* The service accepts Dispatchable implementations to its internal and external lists.
* When a client invokes dispatch the implementation first invokes all internal Dispatchable
* instances then all external Dispatchable instances. Dispatchables are invoked
* in the same order they are added. Any dispatchable added twice is dispatched once.
*
* <p>Note: Each execution thread owns its own dispatch queue.
*
* Note: Dispatchs could result in further call to the dispatch service. This is because listener code
* that is invoked as a result of a dispatch may create patterns that fireStatementStopped as soon as they are started
* resulting in further dispatches within the same thread. Thus the implementation class must be careful
* with the use of iterators to avoid ConcurrentModificationException errors.
*/
public interface DispatchService
{
/**
* Add a Dispatchable implementation.
* @param dispatchable to execute later
*/
public void addExternal(Dispatchable dispatchable);
/**
* Execute all Dispatchable implementations added to the service since the last invocation of this method.
*/
public void dispatch();
}