MQTT的学习研究（四）moquette-mqtt 的使用之mqtt Blocking API客户端订阅并接收主题信息

在上面两篇关于mqtt的broker的启动和mqtt的服务端发布主题信息之后，我们客户端需要订阅相关的信息并接收相关的主题信息。

package com.etrip.mqtt;import java.net.URISyntaxException;import org.fusesource.mqtt.client.BlockingConnection;import org.fusesource.mqtt.client.MQTT;import org.fusesource.mqtt.client.Message;import org.fusesource.mqtt.client.QoS;import org.fusesource.mqtt.client.Topic;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** *  * MQTT moquette 的Client 段用于订阅主题，并接收主题信息 *  * 采用阻塞式 订阅主题  *  * @author longgangbai */public class MQTTClient {  private static final Logger LOG = LoggerFactory.getLogger(MQTTClient.class);private final static String CONNECTION_STRING = "tcp://192.168.208.46:1883";private final static boolean CLEAN_START = true;private final static short KEEP_ALIVE = 30;// 低耗网络，但是又需要及时获取数据，心跳30sprivate final static String CLIENT_ID = "publishService";public  static Topic[] topics = {    new Topic("china/beijing", QoS.EXACTLY_ONCE),    new Topic("china/tianjin", QoS.AT_LEAST_ONCE),    new Topic("china/henan", QoS.AT_MOST_ONCE)};public final  static long RECONNECTION_ATTEMPT_MAX=6;public final  static long RECONNECTION_DELAY=2000;public final static int SEND_BUFFER_SIZE=2*1024*1024;//发送最大缓冲为2M  public static void main(String[] args)   {//创建MQTT对象    MQTT mqtt = new MQTT();    BlockingConnection connection=null;    try {    //设置mqtt broker的ip和端口mqtt.setHost(CONNECTION_STRING);//连接前清空会话信息mqtt.setCleanSession(CLEAN_START);//设置重新连接的次数mqtt.setReconnectAttemptsMax(RECONNECTION_ATTEMPT_MAX);//设置重连的间隔时间mqtt.setReconnectDelay(RECONNECTION_DELAY);//设置心跳时间mqtt.setKeepAlive(KEEP_ALIVE);//设置缓冲的大小mqtt.setSendBufferSize(SEND_BUFFER_SIZE);//获取mqtt的连接对象BlockingConnection    connection = mqtt.blockingConnection();    //MQTT连接的创建     connection.connect();    //创建相关的MQTT 的主题列表     Topic[] topics = {new Topic("china/beijing", QoS.AT_LEAST_ONCE)};    //订阅相关的主题信息     byte[] qoses = connection.subscribe(topics);    //    while(true){    //接收订阅的消息内容    Message message = connection.receive();    //获取订阅的消息内容     byte[] payload = message.getPayload();    // process the message then:    LOG.info("MQTTClient Message  Topic="+message.getTopic()+" Content :"+new String(payload));    //签收消息的回执    message.ack();        Thread.sleep(2000);    }} catch (URISyntaxException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{try {connection.disconnect();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}}}