NtpBinding.java

/**
 * Copyright (c) 2010-2016 by the respective copyright holders.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.openhab.binding.ntp.internal;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Dictionary;
import java.util.Locale;
import java.util.TimeZone;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.net.ntp.NTPUDPClient;
import org.apache.commons.net.ntp.TimeInfo;
import org.openhab.binding.ntp.NtpBindingProvider;
import org.openhab.core.binding.AbstractActiveBinding;
import org.openhab.core.binding.BindingProvider;
import org.openhab.core.library.types.DateTimeType;
import org.osgi.service.cm.ConfigurationException;
import org.osgi.service.cm.ManagedService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * The NTP Refresh Service polls the configured timeserver with a configurable
 * interval and posts a new event of type ({@link DateTimeType} to the event bus.
 * The interval is 15 minutes by default and can be changed via openhab.cfg.
 *
 * @author Thomas.Eichstaedt-Engelen
 * @since 0.8.0
 */
public class NtpBinding extends AbstractActiveBinding<NtpBindingProvider>implements ManagedService {

    private static final Logger logger = LoggerFactory.getLogger(NtpBinding.class);

    /** timeout for requests to the NTP server */
    private static final int NTP_TIMEOUT = 5000;

    // List of time servers: http://tf.nist.gov/service/time-servers.html
    protected String hostname = "ptbtime1.ptb.de";

    /** Default refresh interval (currently 15 minutes) */
    private long refreshInterval = 900000L;

    /** for logging purposes */
    private final static DateFormat SDF = SimpleDateFormat.getDateTimeInstance(SimpleDateFormat.FULL,
            SimpleDateFormat.FULL);

    @Override
    protected String getName() {
        return "NTP Refresh Service";
    }

    @Override
    protected long getRefreshInterval() {
        return refreshInterval;
    }

    /**
     * @{inheritDoc}
     */
    @Override
    public void execute() {

        if (!bindingsExist()) {
            logger.debug("There is no existing NTP binding configuration => refresh cycle aborted!");
            return;
        }

        long networkTimeInMillis = getTime(hostname);

        logger.debug("Got time from {}: {}", hostname, SDF.format(new Date(networkTimeInMillis)));

        for (NtpBindingProvider provider : providers) {
            for (String itemName : provider.getItemNames()) {
                updateTime(provider, itemName, networkTimeInMillis);
            }
        }

    }

    private void updateTime(NtpBindingProvider provider, String itemName, long networkTimeInMillis) {
        TimeZone timeZone = provider.getTimeZone(itemName);
        Locale locale = provider.getLocale(itemName);

        Calendar calendar = Calendar.getInstance(timeZone, locale);
        calendar.setTimeInMillis(networkTimeInMillis);

        eventPublisher.postUpdate(itemName, new DateTimeType(calendar));
    }

    /**
     * Queries the given timeserver <code>hostname</code> and returns the time
     * in milliseconds.
     *
     * @param hostname the timeserver to query
     * @return the time in milliseconds or the current time of the system if an
     *         error occurs.
     */
    protected static long getTime(String hostname) {

        try {
            NTPUDPClient timeClient = new NTPUDPClient();
            timeClient.setDefaultTimeout(NTP_TIMEOUT);
            InetAddress inetAddress = InetAddress.getByName(hostname);
            TimeInfo timeInfo = timeClient.getTime(inetAddress);

            return timeInfo.getReturnTime();
        } catch (UnknownHostException uhe) {
            logger.warn("the given hostname '{}' of the timeserver is unknown -> returning current sytem time instead",
                    hostname);
        } catch (IOException ioe) {
            logger.warn("couldn't establish network connection [host '{}'] -> returning current sytem time instead",
                    hostname);
        }

        return System.currentTimeMillis();
    }

    protected void addBindingProvider(NtpBindingProvider bindingProvider) {
        super.addBindingProvider(bindingProvider);
    }

    protected void removeBindingProvider(NtpBindingProvider bindingProvider) {
        super.removeBindingProvider(bindingProvider);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    @SuppressWarnings("rawtypes")
    public void updated(Dictionary config) throws ConfigurationException {

        if (config != null) {
            String hostnameString = (String) config.get("hostname");
            if (StringUtils.isNotBlank(hostnameString)) {
                hostname = hostnameString;
            }

            String refreshIntervalString = (String) config.get("refresh");
            if (StringUtils.isNotBlank(refreshIntervalString)) {
                refreshInterval = Long.parseLong(refreshIntervalString);
            }

            setProperlyConfigured(true);
        }

    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void bindingChanged(BindingProvider provider, String itemName) {
        NtpGenericBindingProvider ntpBindingProvider = (NtpGenericBindingProvider) provider;
        if (ntpBindingProvider.providesBindingFor(itemName)) {
            long networkTimeInMillis = getTime(hostname);
            updateTime(ntpBindingProvider, itemName, networkTimeInMillis);
        }
        super.bindingChanged(provider, itemName);
    }

}