Tolerate null return from getNegotiatedExtensions (for Jetty 9.4.1 compatibility) [SPR-15180]

[spring-projects-issues]

Andy Wilkinson opened SPR-15180 and commented

Jetty 9.4.1 may return null from javax.websocket.Session.getNegotiatedExtensions() rather than an empty list. This causes a NullPointerException in StandardWebSocketSession:

java.io.IOException: Connect failure
	at org.eclipse.jetty.websocket.jsr356.ClientContainer.connect(ClientContainer.java:165) ~[javax-websocket-client-impl-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.websocket.jsr356.ClientContainer.connectToServer(ClientContainer.java:188) ~[javax-websocket-client-impl-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.springframework.web.socket.client.standard.StandardWebSocketClient$1.call(StandardWebSocketClient.java:150) ~[spring-websocket-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.socket.client.standard.StandardWebSocketClient$1.call(StandardWebSocketClient.java:147) ~[spring-websocket-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_102]
	at java.lang.Thread.run(Thread.java:745) [na:1.8.0_102]
Caused by: java.lang.NullPointerException: null
	at org.springframework.web.socket.adapter.standard.StandardWebSocketSession.initializeNativeSession(StandardWebSocketSession.java:185) ~[spring-websocket-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.springframework.web.socket.adapter.standard.StandardWebSocketHandlerAdapter.onOpen(StandardWebSocketHandlerAdapter.java:61) ~[spring-websocket-4.3.5.RELEASE.jar:4.3.5.RELEASE]
	at org.eclipse.jetty.websocket.jsr356.endpoints.JsrEndpointEventDriver.onConnect(JsrEndpointEventDriver.java:140) ~[javax-websocket-client-impl-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.websocket.common.events.AbstractEventDriver.openSession(AbstractEventDriver.java:233) ~[websocket-common-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.websocket.jsr356.endpoints.AbstractJsrEventDriver.openSession(AbstractJsrEventDriver.java:104) ~[javax-websocket-client-impl-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.websocket.common.WebSocketSession.open(WebSocketSession.java:504) ~[websocket-common-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.websocket.common.WebSocketSession.onOpened(WebSocketSession.java:433) ~[websocket-common-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.io.AbstractConnection.onOpen(AbstractConnection.java:200) ~[jetty-io-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.onOpen(AbstractWebSocketConnection.java:566) ~[websocket-common-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.io.AbstractEndPoint.upgrade(AbstractEndPoint.java:432) ~[jetty-io-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.websocket.client.WebSocketUpgradeRequest.upgrade(WebSocketUpgradeRequest.java:622) ~[websocket-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.http.HttpChannelOverHTTP.exchangeTerminating(HttpChannelOverHTTP.java:116) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.HttpReceiver.terminateResponse(HttpReceiver.java:451) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.HttpReceiver.responseSuccess(HttpReceiver.java:405) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.messageComplete(HttpReceiverOverHTTP.java:281) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.http.HttpParser.parseHeaders(HttpParser.java:1076) ~[jetty-http-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:1326) ~[jetty-http-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.parse(HttpReceiverOverHTTP.java:170) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.process(HttpReceiverOverHTTP.java:131) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.receive(HttpReceiverOverHTTP.java:70) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.http.HttpChannelOverHTTP.receive(HttpChannelOverHTTP.java:130) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.client.http.HttpConnectionOverHTTP.onFillable(HttpConnectionOverHTTP.java:116) ~[jetty-client-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:279) ~[jetty-io-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:112) ~[jetty-io-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:124) ~[jetty-io-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:672) ~[jetty-util-9.4.1.v20170120.jar:9.4.1.v20170120]
	at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:590) ~[jetty-util-9.4.1.v20170120.jar:9.4.1.v20170120]
	... 1 common frames omitted

It's not clear if this is spec compliant (both the spec and the javadoc are silent on it), but could StandardWebSocketSession be made more robust and treat null as an empty list?

---

Affects: 4.3.5

Reference URL: spring-projects/spring-boot#7750

[spring-projects-issues]

Juergen Hoeller commented

I've revised our WebSocketSession contract along with this, defining to return always an empty list there for our own getExtensions variant... which was allowing a null return value but all implementations except one returned an empty list already.