浅谈Spring Session工作原理

<!-- spring session -->
  <filter>
    <filter-name>springSessionRepositoryFilter</filter-name>
    <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>springSessionRepositoryFilter</filter-name>
    <url-pattern>
    private void touch(String key) {
        //并不是直接删除 key，而只是访问 key，通过惰性删除确保spring:session:sessions:expires键实时删除，
        // 同时也保证多线程并发续签的场景下，key移动到不同spring:session:expirations键里面时，
        //以spring:session:sessions:expires键实际ttl时间为准
        this.redis.hasKey(key);
    }

public void configure(RedisConnection connection) {
       String notifyOptions = getNotifyOptions(connection);
       String customizedNotifyOptions = notifyOptions;
       if (!customizedNotifyOptions.contains("E")) {
           customizedNotifyOptions += "E";
       }
       boolean A = customizedNotifyOptions.contains("A");
       if (!(A || customizedNotifyOptions.contains("g"))) {
           customizedNotifyOptions += "g";
       }
       if (!(A || customizedNotifyOptions.contains("x"))) {
           customizedNotifyOptions += "x";
       }
       if (!notifyOptions.equals(customizedNotifyOptions)) {
           connection.setConfig(CONFIG_NOTIFY_KEYSPACE_EVENTS, customizedNotifyOptions);
       }
   }

@Bean
 public RedisMessageListenerContainer redisMessageListenerContainer(
         RedisConnectionFactory connectionFactory,
         RedisOperationsSessionRepository messageListener) {
             ......
     //psubscribe del和expired事件
     container.addMessageListener(messageListener,
             Arrays.asList(new PatternTopic("__keyevent@*:del"),
                     new PatternTopic("__keyevent@*:expired")));
     //psubscribe created事件
     container.addMessageListener(messageListener, Arrays.asList(new PatternTopic(
             messageListener.getSessionCreatedChannelPrefix() + "*")));
     return container;
 }

public void onMessage(Message message, byte[] pattern) {
      ......
      if (channel.startsWith(getSessionCreatedChannelPrefix())) {
          ...
          //处理spring:session created事件
          handleCreated(loaded, channel);
          return;
      }
 
      //非spring:session:sessions:expires事件不做处理
      String body = new String(messageBody);
      if (!body.startsWith(getExpiredKeyPrefix())) {
          return;
      }
 
      boolean isDeleted = channel.endsWith(":del");
      if (isDeleted || channel.endsWith(":expired")) {
          ......
          if (isDeleted) {
              //处理spring:session:sessions:expires del事件
              handleDeleted(sessionId, session);
          }
          else {
              //处理spring:session:sessions:expires expired事件
              handleExpired(sessionId, session);
          }
          ......
          return;
      }
  }

@Component
public class SessionExpiredListener implements ApplicationListener<SessionExpiredEvent> {
    @Override
    public void onApplicationEvent(SessionExpiredEvent event) {
        ......
    }
}