NullPointerException in sessionDestroyed listener

[bpapez]

We are using Spring Session version 1.1.1.RELEASE with Redis and sometimes see the following stacktrace in the log:

2016-04-20 11:07:33,986: ERROR [RedisOperationsSessionRepository] - Error publishing org.springframework.session.events.SessionExpiredEvent[source=org.springframework.session.data.redis.RedisOperationsSessionRepository@3ec0b82f].
java.lang.NullPointerException
       at org.springframework.session.web.http.ExpiringSessionHttpSession.getId(ExpiringSessionHttpSession.java:61)
       at org.jahia.bin.listeners.JahiaContextLoaderListener.sessionDestroyed(JahiaContextLoaderListener.java:446)
       at org.springframework.session.web.http.SessionEventHttpSessionListenerAdapter.onApplicationEvent(SessionEventHttpSessionListenerAdapter.java:62)
       at org.springframework.session.web.http.SessionEventHttpSessionListenerAdapter.onApplicationEvent(SessionEventHttpSessionListenerAdapter.java:40)
       at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:96)
       at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:334)
       at org.springframework.session.data.redis.RedisOperationsSessionRepository.publishEvent(RedisOperationsSessionRepository.java:557)
       at org.springframework.session.data.redis.RedisOperationsSessionRepository.handleExpired(RedisOperationsSessionRepository.java:549)
       at org.springframework.session.data.redis.RedisOperationsSessionRepository.onMessage(RedisOperationsSessionRepository.java:515)
       at org.springframework.data.redis.listener.RedisMessageListenerContainer.executeListener(RedisMessageListenerContainer.java:245)
       at org.springframework.data.redis.listener.RedisMessageListenerContainer.processMessage(RedisMessageListenerContainer.java:235)
       at org.springframework.data.redis.listener.RedisMessageListenerContainer$1.run(RedisMessageListenerContainer.java:960)
       at java.lang.Thread.run(Thread.java:745)

Is this a bug or an expected behaviour? Do we have to expect that NullPointerException or could it be prevented?

[rwinch]

@bpapez Thanks for the report!

As noted on the javadoc for getSession() it is possible for the Session to be null:

Gets the Session that was destroyed. For some SessionRepository implementations it may not be possible to get the original session in which case this may be null.

If you want to guarantee obtaining the session id, you can get it from getSessionId()

What is interesting is that you are getting a null value for the Redis implementation. As of 1.1 sessions created by Spring Session's Redis implementation should be be non-null. Did you by chance use Spring Session prior to 1.1? If so, the sessions that are null might be a session that was originally created before. In that case it would be expected that the session is null.

[bpapez]

No, we have never used Spring Session version prior to 1.1.0. That's the version we started with. We have just switched to 1.1.1 a week ago. Notice that we never got null on HttpSessionEvent.getSession(). However we get a NullPointerException, when calling getId() on that session object then.

[rwinch]

@bpapez Thanks for the response.

Notice that we never got null on HttpSessionEvent.getSession(). However we get a NullPointerException, when calling getId() on that session object then.

That is a good point. This looks like a bug, but I'm not certain what is causing it at the moment.

[LintelXu]

Got the same problem when using 1.2.1.RELEASE, have you solved it? @bpapez @rwinch

[bpapez]

@Lintel-X no, unfortunately I did not have time to work on it further.

[LintelXu]

@bpapez Thanks for your apply