redis發佈訂閱Java代碼實現

Redis除了能夠用做緩存數據外，另外一個重要用途是它實現了發佈訂閱(pub/sub)消息通訊模式：發送者(pub)發送消息，訂閱者(sub)接收消息。

爲了實現redis的發佈訂閱機制，首先要打開redis服務；其次，引入redis須要的jar包，在pom.xml配置文件加入如下代碼：

<dependency>
<groupId>redis.clients</groupId>
<artifactId>jedis</artifactId>
<version>2.1.0</version>
</dependency>

因爲訂閱消息通道須要再tomcat啓動時觸發，所以，須要建立一個listener監聽器，在監聽器裏實現redis訂閱，在web.xml裏配置監聽器以下：

<listener>
<listener-class>com.test.listener.InitListener</listener-class>
</listener>

1、訂閱消息（InitListener實現）

redis支持多通道訂閱，一個客戶端能夠同時訂閱多個消息通道，以下代碼所示，訂閱了13個通道。因爲訂閱機制是線程阻塞的，須要額外開啓一個線程專門用於處理訂閱消息及接收消息處理。

複製代碼
public class InitListener implements ServletContextListener{
private Logger logger = Logger.getLogger(InitListener.class);

@Override
public void contextInitialized(ServletContextEvent sce) {
    logger.info("啓動tomcat");// 鏈接redis
    Map<String, String> proMap = PropertyReader.getProperties();
    final String url = proMap.get("redis.host");
    final Integer port = Integer.parseInt(proMap.get("redis.port"));
    final ClassPathXmlApplicationContext classPathXmlApplicationContext = new ClassPathXmlApplicationContext("classpath*:applicationContext.xml");
    final RedisSubListener redisSubListener = (RedisSubListener) classPathXmlApplicationContext.getBean("redisSubListener");
    // 爲防止阻塞tomcat啓動，開啓線程執行
    new Thread(new Runnable(){  
        public void run(){  
            // 鏈接redis,創建監聽
            Jedis jedis = null;
            while(true){
                //解碼資源更新通知,畫面選看回復,畫面選看中止回覆,預案啓動,預案中止,輪切啓動,輪切中止,預案啓動回覆,預案中止回覆,輪切啓動回覆,輪切中止回覆,監視屏分屏狀態通知,畫面狀態通知
                String[] channels = new String[] { "decodeResourceUpdateNtf", "tvSplitPlayRsp","tvSplitPlayStopRsp",
                        "planStartStatusNtf", "planStopStatusNtf", "pollStartStatusNtf", "pollStopStatusNtf",
                        "planStartRsp","planStopRsp","pollStartRsp","pollStopRsp","tvSplitTypeNtf","tvSplitStatusNtf"};
                try{
                    jedis = new Jedis(url,port);
                    logger.info("redis請求訂閱通道");
                    jedis.subscribe(redisSubListener,channels);
                    logger.info("redis訂閱結束");
                }catch(JedisConnectionException e){
                    logger.error("Jedis鏈接異常,異常信息 :" + e);
                }catch(IllegalStateException e){
                     logger.error("Jedis異常,異常信息 :" + e);
                }

                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                if(jedis != null){
                    jedis = null;
                }
            }
        }})
    .start();
}

複製代碼
最後在spring配置文件裏接入如下配置：

複製代碼
<!-- redis -->
<bean id="redisMessageService" class="com.test.service.impl.RedisMessageServiceImpl" scope="singleton">
<property name="webSocketService"><ref local="webSocketService" /></property>
<property name="tvSplitStatusDao" ref="tvSplitStatusDao"></property>
</bean>
<bean id="redisSubListener" class="com.test.common.RedisSubListener" scope="singleton">
<property name="redisMessageService"><ref local="redisMessageService" /></property>
</bean>
複製代碼
RedisMessageServiceImpl用於處理接收的redis消息。
2、發佈消息

複製代碼
public class RedisPublishUtil {
private Logger logger = Logger.getLogger(RedisPublishUtil.class);
public static Jedis pubJedis;
private static Map<String, String> proMap = PropertyReader.getProperties();
private static final String redisPort = proMap.get("redis.port");
private static String url = proMap.get("redis.host");
private static final int port = Integer.parseInt(redisPort);

public void setPubJedis(Jedis jedis) {
    RedisPublishUtil.pubJedis = jedis;
}

public Jedis getPubJedis() {
    if (pubJedis == null) {
        createJedisConnect();
    }
    // 返回對象
    return pubJedis;
}

public Jedis createJedisConnect(){
    // 鏈接redis
    logger.info("===建立鏈接jedis=====");
    try {
        pubJedis = new Jedis(url, port);
    } catch (JedisConnectionException e) {
        logger.error("Jedis鏈接異常,異常信息 :" + e.getMessage());
        try {
            Thread.sleep(1000);
            logger.info("發起從新鏈接jedis");
            createJedisConnect();
        } catch (InterruptedException except) {
            except.printStackTrace();
        }
    }
    // 返回對象
    return pubJedis;
}
//公共發佈接口
public void pubRedisMsg(String msgType,String msg){
    logger.info("redis準備發佈消息內容：" + msg);
    try {
        this.getPubJedis().publish(msgType, msg);

    } catch (JedisConnectionException e) {
        logger.error("redis發佈消息失敗！", e);
        this.setPubJedis(null);
        logger.info("從新發布消息，channel="+msgType);
        pubRedisMsg(msgType, msg);
    }
}

}
複製代碼
複製代碼
public class PropertyReader {

private static Logger logger = Logger.getLogger(PropertyReader.class);

/*
 * 得到數據庫連接的配置文件
 */
public static Map<String,String> getProperties(){
    logger.info("讀取redis配置文件開始。。。");

     Properties prop = new Properties();     

     Map<String,String> proMap  = new HashMap<String,String>();

    try {
         //讀取屬性文件redis.properties
        InputStream in= PropertyReader.class.getClassLoader().getResourceAsStream("redis.properties");  

        prop.load(in);     ///加載屬性列表
        Iterator<String> it=prop.stringPropertyNames().iterator();
        while(it.hasNext()){
            String key=it.next();
            proMap.put(key, prop.getProperty(key));
        }
        in.close();
        logger.info("讀取redis配置文件成功。。。");
    } catch (Exception e) {
        logger.error("讀取redis配置文件異常！", e);
        e.printStackTrace();
    }
    return proMap;
}

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