mqtt使用二（集成到java代码中）

1.我采用的是springboot，首先pom文件中添加mqtt需要用到的依赖

 <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-integration</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.integration</groupId>
            <artifactId>spring-integration-stream</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.integration</groupId>
            <artifactId>spring-integration-mqtt</artifactId>
        </dependency>


        <dependency>
            <groupId>org.eclipse.paho</groupId>
            <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
            <version>1.2.0</version>
        </dependency>

2.书写客户端，客户端中包括了连接服务器，订阅主题，向主题发布消息的基本操作

import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

/**
 * Description:
 * mqtt客户端
 * @author Victor
 */
@Component
public class MqttPushClient {

    @Autowired
    private PushCallback pushCallback;

    private static final Logger LOGGER = LoggerFactory.getLogger(MqttPushClient.class);

    private static MqttClient client;

    public static MqttClient getClient() {
        return client;
    }

    public static void setClient(MqttClient client) {
        MqttPushClient.client = client;
    }

    /**
     * 连接
     * @param host .
     * @param clientID .
     * @param username .
     * @param password .
     */
    public void connect(String host, String clientID, String username, String password) {
        MqttClient client;
        try {
            client = new MqttClient(host, clientID, new MemoryPersistence());
            MqttConnectOptions options = new MqttConnectOptions();
            options.setCleanSession(false);
            options.setUserName(username);
            options.setPassword(password.toCharArray());
            options.setConnectionTimeout(30);
            options.setKeepAliveInterval(20);
            MqttPushClient.setClient(client);
            try {
                client.setCallback(pushCallback);
                client.connect(options);
            } catch (Exception e) {
                e.printStackTrace();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 发布，默认qos为0，非持久化
     *
     * @param topic       .
     * @param pushMessage .
     */
    public void publish(String topic, String pushMessage) {
        publish(0, false, topic, pushMessage);
    }

    /**
     * 发布主题和消息队列
     *
     * @param qos         .
     * @param retained    .
     * @param topic       .
     * @param pushMessage .
     */
    public void publish(int qos, boolean retained, String topic, String pushMessage) {
        MqttMessage message = new MqttMessage();
        message.setQos(qos);
        message.setRetained(retained);
        message.setPayload(pushMessage.getBytes());
        MqttTopic mTopic = MqttPushClient.getClient().getTopic(topic);
        if (null == mTopic) {
            LOGGER.error("topic not exist");
        }
        MqttDeliveryToken token;
        try {
            token = mTopic.publish(message);
            token.waitForCompletion();
        } catch (MqttPersistenceException e) {
            e.printStackTrace();
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }

    /**
     * 订阅某个主题，qos默认为0
     *
     * @param topic .
     */
    public void subscribe(String topic) {
        subscribe(topic, 0);
    }

    /**
     * 订阅某个主题
     *
     * @param topic .
     * @param qos .
     */
    public void subscribe(String topic, int qos) {
        try {
            MqttPushClient.getClient().subscribe(topic, qos);
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }


}

还有对应回调函数，实现MqttCallback 接口之后要实现三个方法，如果出现需要断开重连操作就在connectionLost方法中操作，如果需要从我们订阅主题拿到数据保存到数据库，那么就在messageArrived方法里操作。SystemConstants是我写的一个

配置连接信息的类，大家改成自己的信息就好了。

import com.alibaba.fastjson.JSONObject;import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.util.StringUtils;

import java.math.BigDecimal;
import java.util.Date;
import java.util.UUID;

/**
 * mqtt回调类
 *
 * @author Victor
 */
@Configuration
public class PushCallback implements MqttCallback {

    @Autowired
    private MqttPushClient mqttPushClient;

    @Autowired
    private DeviceDao deviceDao;

    @Override
    public void connectionLost(Throwable cause) {
        // 连接丢失后，一般在这里面进行重连
        System.out.println("连接断开，可以做重连");
        mqttPushClient.connect(SystemConstants.HOST_URL + ":" + SystemConstants.PORT, "consumer" + SystemConstants.CLIENT_ID, SystemConstants.USERNAME, SystemConstants.PASSWORD);
        mqttPushClient.subscribe("aaa");
    }

    @Override
    public void deliveryComplete(IMqttDeliveryToken token) {
        System.out.println("deliveryComplete---------" + token.isComplete());
    }

    @Override
    public void messageArrived(String topic, MqttMessage message) {
        // subscribe后得到的消息会执行到这里面
        System.out.println("接收消息主题 : " + topic);
        System.out.println("接收消息Qos : " + message.getQos());
        System.out.println("接收消息内容 : " + new String(message.getPayload()));
    }
}

如果想要把mqtt配到application中启动只需要在application启动类中添加PostConstruct注解即可

/**
     * 接受订阅的接口和消息,mqtt消费端
     */
    @PostConstruct
    public void consumeMqttClient() {
        mqttPushClient.connect(SystemConstants.HOST_URL + ":" + SystemConstants.PORT, "consumer" + SystemConstants.CLIENT_ID, SystemConstants.USERNAME, SystemConstants.PASSWORD);
        mqttPushClient.subscribe("aaa");
    }

到此为止，mqtt集成spriongboot就完成了。

新手写博，如有不对请多指教