1.启动容器:docker run -p 1883:1883 -p 8161:8161 -d leo/activemq

如果没有Docker,直接启动ActiveMQ也可以. 

ActiveMQ启动好后,我们只需要写好publisher和subscriber就好了.

2.需要添加2个maven依赖:

		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-all</artifactId>
			<version>5.13.3</version>
		</dependency>

		<dependency>
			<groupId>org.eclipse.paho</groupId>
			<artifactId>org.eclipse.paho.client.mqttv3</artifactId>
			<version>1.1.0</version>
		</dependency>

第一个依赖是activemq的,

第二个依赖的详情,请参考:https://eclipse.org/paho/clients/java/

3.Publisher代码如下:

package leo.mqtt;

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class Publisher {
	public static void main(String[] args) {
		String topic = "TopicOfLeo";
		String content = "Hello Leo!";
		int qos = 1;//0:msg只发1次,并且不需要确认.  1:msg至少发1次,需要确认.   2.发且仅发1次,并且需要进行4次挥手.
		String broker = "tcp://127.0.0.1:1883";
		String clientId = "publisher1";
		MemoryPersistence persistence = new MemoryPersistence();

		try {
			MqttClient client = new MqttClient(broker, clientId, persistence);
			MqttConnectOptions connOpts = new MqttConnectOptions();
			connOpts.setCleanSession(false);//第一次启动是否清除session
			client.connect(connOpts);
			MqttMessage message = new MqttMessage(content.getBytes());
			message.setQos(qos);
			client.publish(topic, message);
			client.disconnect();
			System.exit(0);
		} catch (MqttException me) {
			System.out.println("reason " + me.getReasonCode());
			System.out.println("msg " + me.getMessage());
			System.out.println("loc " + me.getLocalizedMessage());
			System.out.println("cause " + me.getCause());
			System.out.println("excep " + me);
			me.printStackTrace();
		}
	}
}

4.subscriber代码如下:

package leo.mqtt;

import org.eclipse.paho.client.mqttv3.IMqttMessageListener;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class Subscriber {
	public static void main(String[] args) {
		String topic = "TopicOfLeo";
		String broker = "tcp://127.0.0.1:1883";
		String clientId = "Subscriber1";
		MemoryPersistence persistence = new MemoryPersistence();

		try {
			MqttClient client = new MqttClient(broker, clientId, persistence);
			MqttConnectOptions connOpts = new MqttConnectOptions();
			connOpts.setCleanSession(false);
			client.connect(connOpts);
			client.subscribe(topic, new IMqttMessageListener() {

				@Override
				public void messageArrived(String topic, MqttMessage message) throws Exception {
					System.out.println(topic + " -> " + message);
				}
			});
		} catch (MqttException me) {
			System.out.println("reason " + me.getReasonCode());
			System.out.println("msg " + me.getMessage());
			System.out.println("loc " + me.getLocalizedMessage());
			System.out.println("cause " + me.getCause());
			System.out.println("excep " + me);
			me.printStackTrace();
		}
	}
}

5.先运行subscriber,再运行publisher,即可看到效果.

入门demo到此结束.