samples/connectors/src/main/java/org/apache/edgent/samples/connectors/mqtt/SimplePublisherApp.java

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to you under the Apache License, Version 2.0 (the
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  http://www.apache.org/licenses/LICENSE-2.0

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package org.apache.edgent.samples.connectors.mqtt;

import java.io.File;
import java.nio.file.Files;
import java.util.Properties;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.edgent.connectors.mqtt.MqttConfig;
import org.apache.edgent.connectors.mqtt.MqttStreams;
import org.apache.edgent.console.server.HttpServer;
import org.apache.edgent.providers.development.DevelopmentProvider;
import org.apache.edgent.samples.connectors.Util;
import org.apache.edgent.topology.TStream;
import org.apache.edgent.topology.Topology;

/**
 * A simple MQTT publisher topology application.
 */
public class SimplePublisherApp {
    private final Properties props;
    private final String topic;

    public static void main(String[] args) throws Exception {
        if (args.length != 1)
            throw new Exception("missing pathname to mqtt.properties file");
        SimplePublisherApp publisher = new SimplePublisherApp(args[0]);
        publisher.run();
    }

    /**
     * @param mqttPropsPath pathname to properties file
     */
    SimplePublisherApp(String mqttPropsPath) throws Exception {
        props = new Properties();
        props.load(Files.newBufferedReader(new File(mqttPropsPath).toPath()));
        topic = props.getProperty("mqtt.topic");
    }
    
    private MqttConfig createMqttConfig() {
        MqttConfig mqttConfig = MqttConfig.fromProperties(props);
        return mqttConfig;
    }
    
    /**
     * Create a topology for the publisher application and run it.
     */
    private void run() throws Exception {
        DevelopmentProvider tp = new DevelopmentProvider();
        
        // build the application/topology
        
        Topology t = tp.newTopology("mqttSamplePublisher");
        
        // System.setProperty("javax.net.debug", "ssl"); // or "all"; "help" for full list

        // Create the MQTT broker connector
        MqttConfig mqttConfig = createMqttConfig();
        MqttStreams mqtt = new MqttStreams(t, () -> mqttConfig);
        
        // Create a sample stream of tuples to publish
        AtomicInteger cnt = new AtomicInteger();
        TStream<String> msgs = t.poll(
                () -> {
                    String msg = String.format("Message-%d from %s",
                            cnt.incrementAndGet(), Util.simpleTS());
                    System.out.println("poll generated msg to publish: " + msg);
                    return msg;
                }, 1L, TimeUnit.SECONDS);
        
        // Publish the stream to the topic.  The String tuple is the message value.
        mqtt.publish(msgs, topic, 0/*qos*/, false/*retain*/);
        
        // run the application / topology
        System.out.println("Console URL for the job: "
                + tp.getServices().getService(HttpServer.class).getConsoleUrl());
        tp.submit(t);
    }

}