MqttPersistencePublisher.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.persistence.mqtt.internal;

import static java.lang.String.format;
import static java.lang.System.currentTimeMillis;
import static org.apache.commons.lang.StringUtils.trimToEmpty;

import org.openhab.core.items.Item;
import org.openhab.core.library.types.DateTimeType;
import org.openhab.core.library.types.DecimalType;
import org.openhab.core.library.types.OnOffType;
import org.openhab.core.library.types.OpenClosedType;
import org.openhab.core.library.types.UpDownType;
import org.openhab.io.transport.mqtt.MqttMessageProducer;
import org.openhab.io.transport.mqtt.MqttSenderChannel;

/**
 * MQTT Message publisher for composing and sending persistence messages.
 *
 * @author Davy Vanherbergen
 * @since 1.3.0
 */
public class MqttPersistencePublisher implements MqttMessageProducer {

    private MqttSenderChannel channel;

    private String messageTemplate;

    private String topic;

    /**
     * Initialize publisher with a given topic and template.
     * 
     * @param topic
     *            MQTT publish topic.
     * @param messageTemplate
     *            message payload template.
     */
    public MqttPersistencePublisher(String topic, String messageTemplate) {
        this.topic = topic;
        this.messageTemplate = messageTemplate;
    }

    @Override
    public void setSenderChannel(MqttSenderChannel channel) {
        this.channel = channel;
    }

    /**
     * Publish a persistence message for a given item.
     * 
     * Topic and template will be reformatted by String.format using the
     * following parameters:
     * 
     * <pre>
     * 	%1 item name 
     * 	%2 alias (as defined in mqtt.persist)
     * 	%3 item state 
     * 	%4 current timestamp
     * </pre>
     * 
     * @param item
     *            item which to persist the state of.
     * @param alias
     *            null or as defined in persistence configuration.
     * @throws Exception
     *             when no MQTT message could be sent.
     */
    public void publish(Item item, String alias) throws Exception {

        Object state = item.getState().toString();

        if (item.getState() instanceof DecimalType) {
            state = ((DecimalType) item.getState()).toBigDecimal();
        } else if (item.getState() instanceof DateTimeType) {
            state = ((DateTimeType) item.getState()).getCalendar();
        } else if (item.getState() instanceof OnOffType) {
            state = item.getState().equals(OnOffType.ON) ? "1" : "0";
        } else if (item.getState() instanceof OpenClosedType) {
            state = item.getState().equals(OpenClosedType.OPEN) ? "1" : "0";
        } else if (item.getState() instanceof UpDownType) {
            state = item.getState().equals(UpDownType.UP) ? "1" : "0";
        }

        String message = format(messageTemplate, item.getName(), trimToEmpty(alias), state, currentTimeMillis());
        String destination = format(topic, item.getName(), trimToEmpty(alias), state, currentTimeMillis());

        channel.publish(destination, message.getBytes());
    }

}