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https://issues.apache.org/jira/browse/LOG4J2-1184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14979739#comment-14979739
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Robert Veitch commented on LOG4J2-1184:
---------------------------------------
Sure! Below is a sample class to demonstrate what I'm seeing, tested against
log4j2 2.2.
package com.test;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.util.Cancellable;
import org.apache.logging.log4j.core.util.DefaultShutdownCallbackRegistry;
public class CustomShutdownCallbackRegistry extends
DefaultShutdownCallbackRegistry {
private static Logger logger =
LogManager.getLogger(CustomShutdownCallbackRegistry.class);
public static void main(final String[] args) {}
@Override
public Cancellable addShutdownCallback(final Runnable callback) {
logger.info("msg");
return super.addShutdownCallback(callback);
}
}
And then I call this class using the following system property:
-Dlog4j.shutdownCallbackRegistry=com.test.CustomShutdownCallbackRegistry
The stack trace is below:
Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: java.lang.NullPointerException
at
com.test.CustomShutdownCallbackRegistry.addShutdownCallback(CustomShutdownCallbackRegistry.java:15)
at
org.apache.logging.log4j.core.impl.Log4jContextFactory.addShutdownCallback(Log4jContextFactory.java:235)
at
org.apache.logging.log4j.core.LoggerContext.setUpShutdownHook(LoggerContext.java:179)
at
org.apache.logging.log4j.core.LoggerContext.start(LoggerContext.java:140)
at
org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:147)
at
org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:41)
at org.apache.logging.log4j.LogManager.getContext(LogManager.java:175)
at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:426)
at
com.test.CustomShutdownCallbackRegistry.<clinit>(CustomShutdownCallbackRegistry.java:9)
Perhaps it is my misunderstanding, are we not expected to be able to use log4j
loggers within a custom ShutdownCallbackRegistry?
> NullPointerException when attempting to configure logging in custom
> ShutdownCallbackRegistry
> --------------------------------------------------------------------------------------------
>
> Key: LOG4J2-1184
> URL: https://issues.apache.org/jira/browse/LOG4J2-1184
> Project: Log4j 2
> Issue Type: Bug
> Affects Versions: 2.2
> Environment: OSX, Ubuntu
> Reporter: Robert Veitch
> Priority: Minor
>
> I have a custom ShutdownCallbackRegistry implementation, which I've
> configured to be instantiated via:
> -Dlog4j.shutdownCallbackRegistry=<my_implementation>
> If I configure a logger in the normal way, either via a static or instance
> variable, I get a NullPointerException on startup. Something like:
> private static final Logger logger = LoggerFactory.getLogger(MyClass.class);
> I think this is probably because the configured registry instance gets
> created prior to the log4j subsystem responsible for loggers. My workaround
> is to define the logger variable without assigning it:
> private static final Logger logger;
> And then assigning it as the first line of my run method:
> public void run() {
> logger = LoggerFactory.getLogger(MyClass.class);
> // shutdown registry code
> }
> But if possible, it seems like the instantiation order should be reworked so
> that implementers of a custom registry do not have to do this.
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