Hi Mike, sorry for the late answer. I hope this still helps you. This stackoverflow answer solves your problem: https://stackoverflow.com/questions/2411487/nullpointerexception-in-java-wit... TL;DR: You are running into a hotspot optimisation and need to add -XX:-OmitStackTraceInFastThrow to your JVM options to “enable” those stacktraces. Cheers, Jörn. On 10. June 2020 at 04:52:38, 陌路人 (h5ru@qq.com) wrote: Hi, Firstly thank you for your time. Sometimes, logback does not print exception's cause, I can't use the log to fix bug, as followings: 2020-06-09 16:54:32,393 ERROR [task-executor-27] [SimpleDispatcher.java:203] Exception occurred during dispatch web socket frame for uri[/ws/partydungeon/move] by uid[6493203]. java.lang.reflect.InvocationTargetException: null at sun.reflect.*GeneratedMethodAccessor100*.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at com.mitu.game.dispatcher.SimpleDispatcher$EventRunnable.doWebSocketMessage(SimpleDispatcher.java:187) at com.mitu.game.dispatcher.SimpleDispatcher$EventRunnable.run(SimpleDispatcher.java:106) at com.mitu.game.wrapper.ThreadPoolTaskExecutorEx$SafeRunnable.run(ThreadPoolTaskExecutorEx.java:74) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: java.lang.NullPointerException: null 2020-06-09 16:54:32,405 INFO [nioEventLoopGroup-3-4] [SimpleLoggingHandler.java:35] IN {uid=5589867, forward=183.200.25.192, 183.200.25.192:24172, type=websocket, uri=/ws/user/bind, ts=1591692869} / 10.0.0.70:34948 10 And the code is like: private void doWebSocketMessage(Event event) { String uri = "some uri"; String uid = "some id"; try { Object ret = action.method.invoke(action.instance, event.getData(), new Object[]{event}); } catch (Exception ex) { logger.error(String.format("Exception occurred during dispatch web socket frame for uri[%s] by uid[%s].", uri, uid), ex); } } I tried to look for answers by google and bing, but failed, and I tried to reproduce this problem, failed too, the cause can be printed, and it likes: java.lang.reflect.InvocationTargetException: null at sun.reflect.*NativeMethodAccessorImpl*.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at com.mitu.game.Application.main(Application.java:54) Caused by: java.lang.NullPointerException: null at com.mitu.game.Application$T.f(Application.java:42) ... 5 common frames omitted the difference is NativeMethodAccessorImpl vs GeneratedMethodAccessor100, is it matter? I steped into the logback code, maybe the target of the exception is null, but I do not know the reason:( Thank you again, for your patient, and sorry for my poor english:( BR, Mike Yu _______________________________________________ logback-user mailing list logback-user@qos.ch http://mailman.qos.ch/mailman/listinfo/logback-user