JMSApplicationListener.java

/* Copyright (c) 2011 GeoSolutions - http://www.geo-solutions.it/.  All rights reserved.
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package it.geosolutions.geoserver.jms;

import java.util.logging.Level;
import java.util.logging.Logger;

import it.geosolutions.geoserver.jms.configuration.JMSConfiguration;
import it.geosolutions.geoserver.jms.configuration.ToggleConfiguration;
import it.geosolutions.geoserver.jms.events.ToggleEvent;
import it.geosolutions.geoserver.jms.events.ToggleType;

import javax.annotation.PostConstruct;

import org.geotools.util.logging.Logging;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;

/**
 * 
 * This class make it possible to enable and disable the Event producer/consumer using Applications Events.
 * 
 * This is used at the GeoServer startup to disable the producer until the initial configuration is loaded.
 * 
 * It can also be used to enable/disable the producer in a Master+Slave configuration to avoid recursive event production.
 * 
 * @see {@link ToggleEvent}
 * 
 * @author Carlo Cancellieri - carlo.cancellieri@geo-solutions.it
 * 
 */
public class JMSApplicationListener implements ApplicationListener<ApplicationEvent> {

	private final static Logger LOGGER = Logging.getLogger(JMSApplicationListener.class);

    protected final ToggleType type;

    /**
     * This will be set to false:<br/>
     * - until the GeoServer context is initialized<br/>
     * - if this instance of geoserver act as pure slave
     */
    private volatile Boolean status=false;
    
    @Autowired
    public JMSConfiguration config;

    public JMSApplicationListener(ToggleType type) {
        this.type = type;
    }
    
    @PostConstruct
    private void init(){
        setStatus(getStatus(type, config));
    }
    
    public static boolean getStatus(final ToggleType type, JMSConfiguration config){
        Object statusObj;
        if (type.equals(ToggleType.SLAVE)) {
            statusObj = config.getConfiguration(ToggleConfiguration.TOGGLE_SLAVE_KEY);
            if (statusObj==null){
                statusObj=ToggleConfiguration.DEFAULT_SLAVE_STATUS;
            }
        } else {
            statusObj = config.getConfiguration(ToggleConfiguration.TOGGLE_MASTER_KEY);
            if (statusObj==null){
                statusObj=ToggleConfiguration.DEFAULT_MASTER_STATUS;
            }
        }
        return Boolean.parseBoolean(statusObj.toString());
    }


    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (LOGGER.isLoggable(Level.FINE)) {
            LOGGER.fine("Incoming event of type " + event.getClass().getSimpleName());
        }

        if (event instanceof ToggleEvent) {

            // enable/disable the producer
            final ToggleEvent tEv = (ToggleEvent) event;
            if (tEv.getType().equals(this.type)) {
                setStatus(tEv.toggleTo());
            }

        } else {
            if (LOGGER.isLoggable(Level.FINE)) {
                LOGGER.fine("Incoming application event of type "
                        + event.getClass().getSimpleName());
            }
        }
    }

    /**
     * @return the status
     */
    public final boolean isEnabled() {
        return status;
    }

    /**
     * @param status enable or disable producer
     * @note thread safe
     */
    public final void setStatus(final boolean producerEnabled) {
        if (producerEnabled) {
            // if produce is disable -> enable it
            if (!this.status) {
                synchronized (this.status) {
                    if (!this.status) {
                        this.status = true;
                    }
                }
            }
        } else {
            // if produce is Enabled -> disable
            if (this.status) {
                synchronized (this.status) {
                    if (this.status) {
                        this.status = false;
                    }
                }
            }

        }
    }

}