redis发布订阅Java代码实现

Redis除了可以用作缓存数据外，另一个重要用途是它实现了发布订阅(pub/sub)消息通信模式：发送者(pub)发送消息，订阅者(sub)接收消息。

为了实现redis的发布订阅机制，首先要打开redis服务；其次，引入redis需要的jar包，在pom.xml配置文件加入以下代码：

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

由于订阅消息通道需要再tomcat启动时触发，因此，需要创建一个listener监听器，在监听器里实现redis订阅，在web.xml里配置监听器如下：

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

一、订阅消息（InitListener实现）

redis支持多通道订阅，一个客户端可以同时订阅多个消息通道，如下代码所示，订阅了13个通道。由于订阅机制是线程阻塞的，需要额外开启一个线程专门用于处理订阅消息及接收消息处理。

public class InitListener implements ServletContextListener{
    private Logger logger = Logger.getLogger(InitListener.class);
    
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        logger.info("启动tomcat");// 连接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");
        // 为防止阻塞tomcat启动，开启线程执行
        new Thread(new Runnable(){  
            public void run(){  
                // 连接redis,建立监听
                Jedis jedis = null;
                while(true){
                    //解码资源更新通知,画面选看回复,画面选看停止回复,预案启动,预案停止,轮切启动,轮切停止,预案启动回复,预案停止回复,轮切启动回复,轮切停止回复,监视屏分屏状态通知,画面状态通知
                    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请求订阅通道");
                        jedis.subscribe(redisSubListener,channels);
                        logger.info("redis订阅结束");
                    }catch(JedisConnectionException e){
                        logger.error("Jedis连接异常,异常信息 :" + e);
                    }catch(IllegalStateException e){
                         logger.error("Jedis异常,异常信息 :" + e);
                    }
                    
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    if(jedis != null){
                        jedis = null;
                    }
                }
            }})
        .start();
    }

最后在spring配置文件里接入以下配置：

<!-- 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>

RedisMessageServiceImpl用于处理接收的redis消息。

二、发布消息

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();
        }
        // 返回对象
        return pubJedis;
    }
    
    public Jedis createJedisConnect(){
        // 连接redis
        logger.info("===创建连接jedis=====");
        try {
            pubJedis = new Jedis(url, port);
        } catch (JedisConnectionException e) {
            logger.error("Jedis连接异常,异常信息 :" + e.getMessage());
            try {
                Thread.sleep(1000);
                logger.info("发起重新连接jedis");
                createJedisConnect();
            } catch (InterruptedException except) {
                except.printStackTrace();
            }
        }
        // 返回对象
        return pubJedis;
    }
    //公共发布接口
    public void pubRedisMsg(String msgType,String msg){
        logger.info("redis准备发布消息内容：" + msg);
        try {
            this.getPubJedis().publish(msgType, msg);

        } catch (JedisConnectionException e) {
            logger.error("redis发布消息失败！", e);
            this.setPubJedis(null);
            logger.info("重新发布消息，channel="+msgType);
            pubRedisMsg(msgType, msg);
        }
    }

}

public class PropertyReader {

     private static Logger logger = Logger.getLogger(PropertyReader.class);
    
    /*
     * 获得数据库链接的配置文件
     */
    public static Map<String,String> getProperties(){
        logger.info("读取redis配置文件开始。。。");
        
         Properties prop = new Properties();     
        
         Map<String,String> proMap  = new HashMap<String,String>();
         
        try {
             //读取属性文件redis.properties
            InputStream in= PropertyReader.class.getClassLoader().getResourceAsStream("redis.properties");  
            
            prop.load(in);     ///加载属性列表
            Iterator<String> it=prop.stringPropertyNames().iterator();
            while(it.hasNext()){
                String key=it.next();
                proMap.put(key, prop.getProperty(key));
            }
            in.close();
            logger.info("读取redis配置文件成功。。。");
        } catch (Exception e) {
            logger.error("读取redis配置文件异常！", e);
            e.printStackTrace();
        }
        return proMap;
    }
}