redis 的发布订阅解决分布式下的websocket session 共享问题

1.项目背景 ：使用websocket 和前端通信但是后端是分布式部署，session 无法共享，并且websocketSession 无法序列化，所以无法把session存到redis 中。

2.基础代码：

@Configuration
@Slf4j
public class RedisConfig {

    @Bean
    public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory,
                                                   MessageListenerAdapter listenerAdapter) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        container.addMessageListener(listenerAdapter, new PatternTopic(Constants.REDIS_CHANNEL));
        return container;
    }

    @Bean
    public MessageListenerAdapter listenerAdapter(RedisReceiver receiver) {
        return new MessageListenerAdapter(receiver, "onMessage");
    }


}

@Slf4j
@Component
public class RedisReceiver implements MessageListener {

    @Autowired
    private TestHandler testHandler;

    @Override
    public void onMessage(Message message, byte[] pattern) {
        try {
            log.info("RedisReceiver onMessage:{}",new String(message.getBody(), StandardCharsets.UTF_8));
            String channel = new String(message.getChannel());
            String content = new String(message.getBody(), StandardCharsets.UTF_8);
            if (Constants.REDIS_CHANNEL.endsWith(channel)) {
                testHandler.sendMessageToClient(content);
            }
        } catch (Exception e) {
            log.error("RedisReceiver 消息处理失败",e);
        }
    }

}

@Slf4j
@Component
public class TestHandler extends TextWebSocketHandler {

    private static final ConcurrentHashMap<String, WebSocketSession> SESSION_DISPATCH_HOLDER = new ConcurrentHashMap<>();


    @Resource
    private StringRedisTemplate stringRedisTemplate;



    @Override
    public void afterConnectionEstablished(@NonNull WebSocketSession session) throws Exception {
        super.afterConnectionEstablished(session);
        SESSION_DISPATCH_HOLDER.put(session.getId(), session);
        log.info("webSocket already connected:{}",session.getId());
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        super.afterConnectionClosed(session, status);
        SESSION_DISPATCH_HOLDER.remove(session.getId());
        log.info("webSocket disConnect:{}",session.getId());
    }

    @Override
    public void handleMessage(WebSocketSession session, WebSocketMessage<?> message) {
        log.info("handleMessage enter message:{}", JsonUtils.objToJsonStr(message.getPayload()));
        TextMessage textMessage = new TextMessage("");
        try {
            session.sendMessage(textMessage);
        } catch (IOException e) {
            log.error("发送消息失败", e);
        }
    }

 

  
    public void sendMessageToClient(String contentList) {
        log.info("sendMessageToClient:{}", contentList);
        if (CollectionUtils.isEmpty(SESSION_DISPATCH_HOLDER)) {
            log.info("没有连接中的客户端");
            return;
        }
        SESSION_DISPATCH_HOLDER.values().parallelStream().forEach(session -> {
            try {
                TextMessage textMessage = new TextMessage(contentList);
                session.sendMessage(textMessage);
                log.info("websocket 消息推送成功:{}", contentList);
            } catch (Exception e) {
                log.error("发送消息失败", e);
            }
        });
    }



}