NullPointerException while registering WebSocket session

Hello,
this is my testing project. I'd like to setup services stack with gateway service, authorization(uaa) service and api service. Api service is used to provide rest/websocket api. Now I'd like to join http session with web socket session to be able to test session timeouts. When I try to create websocket session I'm getting following exception.

java.lang.NullPointerException: null
    at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:936) ~[na:1.8.0_77]
    at org.springframework.session.web.socket.handler.WebSocketRegistryListener.registerWsSession(WebSocketRegistryListener.java:118) ~[spring-session-1.2.1.RELEASE.jar:na]
    at org.springframework.session.web.socket.handler.WebSocketRegistryListener.afterConnectionEstablished(WebSocketRegistryListener.java:86) ~[spring-session-1.2.1.RELEASE.jar:na]
    at org.springframework.session.web.socket.handler.WebSocketRegistryListener.onApplicationEvent(WebSocketRegistryListener.java:67) ~[spring-session-1.2.1.RELEASE.jar:na]
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:166) ~[spring-context-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:138) ~[spring-context-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:382) ~[spring-context-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:336) ~[spring-context-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.session.web.socket.handler.WebSocketConnectHandlerDecoratorFactory$SessionWebSocketHandler.publishEvent(WebSocketConnectHandlerDecoratorFactory.java:84) [spring-session-1.2.1.RELEASE.jar:na]
    at org.springframework.session.web.socket.handler.WebSocketConnectHandlerDecoratorFactory$SessionWebSocketHandler.afterConnectionEstablished(WebSocketConnectHandlerDecoratorFactory.java:78) [spring-session-1.2.1.RELEASE.jar:na]
    at org.springframework.web.socket.handler.WebSocketHandlerDecorator.afterConnectionEstablished(WebSocketHandlerDecorator.java:70) [spring-websocket-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.socket.handler.LoggingWebSocketHandlerDecorator.afterConnectionEstablished(LoggingWebSocketHandlerDecorator.java:48) [spring-websocket-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.socket.handler.ExceptionWebSocketHandlerDecorator.afterConnectionEstablished(ExceptionWebSocketHandlerDecorator.java:48) [spring-websocket-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.socket.sockjs.transport.session.AbstractSockJsSession.delegateConnectionEstablished(AbstractSockJsSession.java:374) [spring-websocket-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.socket.sockjs.transport.session.WebSocketServerSockJsSession.initializeDelegateSession(WebSocketServerSockJsSession.java:159) [spring-websocket-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.socket.sockjs.transport.handler.SockJsWebSocketHandler.afterConnectionEstablished(SockJsWebSocketHandler.java:87) [spring-websocket-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.socket.adapter.standard.StandardWebSocketHandlerAdapter.onOpen(StandardWebSocketHandlerAdapter.java:100) [spring-websocket-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.init(WsHttpUpgradeHandler.java:133) [tomcat-embed-websocket-8.5.4.jar:8.5.4]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:827) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_77]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_77]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_77]

If you need more informations let me know.

Thanks

Start with WebSocketRegistryListener.registerWsSession at line 118 and reproduce the WebSocket connection using the linked OAuth2 testing project. Trace which session value is null; done means the connection no longer throws the reported NullPointerException and session timeout behavior can be tested.