https://issues.apache.org/bugzilla/show_bug.cgi?id=54716
Nick Williams <nicho...@nicholaswilliams.net> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|FIXED |---
--- Comment #2 from Nick Williams <nicho...@nicholaswilliams.net> ---
This definitely improves robustness, but it does not solve the problem where a
NullPointerException is thrown in BackgroundProcessManeger#unregister(...) if a
Session#close(...) is called in an onOpen method:
Caused by: java.lang.NullPointerException
at
org.apache.tomcat.websocket.BackgroundProcessManager.unregister(BackgroundProcessManager.java:75)
at
org.apache.tomcat.websocket.WsWebSocketContainer.unregisterSession(WsWebSocketContainer.java:283)
at
org.apache.tomcat.websocket.server.WsServerContainer.unregisterSession(WsServerContainer.java:283)
at
org.apache.tomcat.websocket.WsSession.sendCloseMessage(WsSession.java:357)
at org.apache.tomcat.websocket.WsSession.close(WsSession.java:305)
at com.wrox.chat.ChatEndpoint.onOpen(ChatEndpoint.java:54)
... 17 more
Calling Session#close(...) from onOpen is a valid use-case: At onOpen I may
check to make sure the user is authenticated, and if not, I need to close the
session.
The root-cause of this NullPointerException is that, in WsWebSocketContainer
and WsProtocolHandler, WsWebSocketContainer#registerSession(...) is called
AFTER onOpen. registerSession ultimately calls
BackgroundProcessManager#register(...), which instantiates the background
thread if it does not already exist. So, if there are NO active Sessions, and a
new Session is created, and that Session is closed onOpen, the background
thread will not already exist when BackgroundProcessManeger#unregister(...) is
called, and that causes the NullPointerException.
There are two possible solutions to this that I can see, though there very well
may be others:
1) In BackgroundProcessManeger#unregister(...), make sure the background thread
is not null before calling #halt().
2) In WsWebSocketContainer and WsProtocolHandler, call registerSession BEFORE
onOpen. This doesn't seem correct to me, but I don't understand it fully.
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