WebSocket is not working with versions of Tomcat other than 8.0.36

Question

I am using JDK 1.8.0_231 and Apache-Tomcat-8.0.36.
I am trying to upgrade Tomcat to version 9.0.
After defining the app to use the new Tomcat version, I am getting a NullPointer exception exception when the app calls flushBatch():

java.lang.NullPointerException
    at org.apache.tomcat.websocket.PerMessageDeflate.sendMessagePart(PerMessageDeflate.java:322)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:284)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:258)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.flushBatch(WsRemoteEndpointImplBase.java:121)
    at org.apache.tomcat.websocket.WsRemoteEndpointBase.flushBatch(WsRemoteEndpointBase.java:48)

This is the code where the app fails:

private void sendMessage(String message, int attemptsNum) throws IOException {
        try {
            if (session.isOpen()) {
                RemoteEndpoint.Basic basicRemote = session.getBasicRemote();
                basicRemote.sendText(message);
                basicRemote.flushBatch();
            }
        } catch (IllegalStateException | NullPointerException | IOException e) {
            ... // handle exception code
        }
    }

This error doesn't happen in Tomcat version 8.0.36.
I also tried to use Tomcat 8.5.50, but got the same exception.

Has anyone encountered this issue?

You shouldn't catch `NullPointerException` that's a very basic thing (although unrelated to this). Is `message` null and other versions started to throw an exception, where 8.0.36 just simply ignores it? — Kayaman, Jan 12 '20 at 15:38
I'm not getting any results in the newer version while in the old one i'm getting the results from the socket. — sky_knight, Jan 12 '20 at 15:55
@sky_knight you didn't answer my question. Is `message` null? — Kayaman, Jan 12 '20 at 16:04
Well, attach the source code to the app and find where line 322 is, find which item is null, and find the connection between that null item and whatever it is you pass to the method. It's likely you are doing something you are not supposed to do - not initializing something properly - and in older versions that may not have been critical, and now it is. — RealSkeptic, Jan 12 '20 at 16:18

WebSocket is not working with versions of Tomcat other than 8.0.36

0 Answers0