What are some scenarios where the Session object expires?

There are several situations in which the Session object becomes invalid.

1. Session timeout: When the maximum lifespan of a session is exceeded, the system will automatically invalidate the session. This timeout duration can be configured in the server’s configuration file.
2. Explicitly expire: Calling the invalidate() method in the program will immediately invalidate the Session object.
3. Server reboot: when the server reboots or redeployed applications, all session objects will be cleared, causing them to become invalid.
4. The SessionID is invalid: When the SessionID in the client’s request is invalid or encounters an error, the server will consider the Session object to be invalid.
5. Concurrency issue: When multiple threads simultaneously manipulate the same Session object, it may lead to the Session object becoming invalid.
6. Problem in a distributed environment: If the Session object is stored on a certain node, and the client request is routed to another node, the Session object may not be found and become invalid.

It is important to note that the expiration of the Session object is managed by the server side and cannot be actively invalidated by the client. The Session can only be indirectly invalidated by sending an invalid SessionID or calling the invalidate() method.