PatternListenerDispatch.java

/**************************************************************************************
 * 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.core.service;

import com.espertech.esper.client.UpdateListener;
import com.espertech.esper.client.EventBean;
import com.espertech.esper.dispatch.Dispatchable;

import java.util.ArrayList;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Dispatchable for dispatching events to update listeners.
 */
public class PatternListenerDispatch implements Dispatchable
{
    private static Log log = LogFactory.getLog(PatternListenerDispatch.class);
    private final Set<UpdateListener> listeners;

    private EventBean singleEvent;
    private ArrayList<EventBean> eventList;

    /**
     * Constructor.
     * @param listeners is the listeners to dispatch to.
     */
    public PatternListenerDispatch(Set<UpdateListener> listeners)
    {
        this.listeners = listeners;
    }

    /**
     * Add an event to be dispatched.
     * @param theEvent to add
     */
    public void add(EventBean theEvent)
    {
        if (singleEvent == null)
        {
            singleEvent = theEvent;
        }
        else
        {
            if (eventList == null)
            {
                eventList = new ArrayList<EventBean>(5);
                eventList.add(singleEvent);
            }
            eventList.add(theEvent);
        }
    }

    public void execute()
    {
        EventBean[] eventArray;

        if (eventList != null)
        {
            eventArray = eventList.toArray(new EventBean[eventList.size()]);
            eventList = null;
            singleEvent = null;
        }
        else
        {
            eventArray = new EventBean[] { singleEvent };
            singleEvent = null;
        }

        for (UpdateListener listener : listeners)
        {
            try
            {
                listener.update(eventArray, null);
            }
            catch (Throwable t)
            {
                String message = "Unexpected exception invoking listener update method on listener class '" + listener.getClass().getSimpleName() +
                        "' : " + t.getClass().getSimpleName() + " : " + t.getMessage();
                log.error(message, t);
            }
        }
    }

    /**
     * Returns true if at least one event has been added.
     * @return true if it has data, false if not
     */
    public boolean hasData()
    {
        if (singleEvent != null)
        {
            return true;
        }
        return false;
    }
}