[logback-user] logback does not print exception's cause

[Jörn Huxhorn]

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-with-no-stacktrace#3010106

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 at 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
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