Configurator.setRootLevel does not work if multi-release jar is not set

[hongwingl]

Description

If multi-release jar is not enabled in fat jar, Configurator.setRootLevel function does not change log level.

Enabling multi-release fixes it.

Could be related to https://issues.apache.org/jira/browse/LOG4J2-2537

The pre java 9 implementation of the function probably does not work and fails silently.

Configuration

Version: 2.24.3

Operating system: Tried both linux and macOS

JDK: jdk17

[ppkarwasz]

@hongwingl,

I don't recommend distributing applications as fat JARs. Using altered versions of a library (repackaged) will cause multiple problems that the author of the fat JAR needs to take care of. See our F.A.Q. entry about single JAR applications for alternative methods to make a single JAR application.

Log4j will issue a WARN statement to the console in case it detects modifications that break location detection:

logging-log4j2/log4j-api/src/main/java/org/apache/logging/log4j/util/StackLocator.java

Lines 94 to 97 in 03cadfa

	LOGGER.warn(
	System.getProperty("java.version", "").startsWith("1.8")
	? "`sun.reflect.Reflection.getCallerClass(int)` is not supported. This will impact location-based features."
	: "Runtime environment or build system does not support multi-release JARs. This will impact location-based features.");

However, it is up to application developer to fix problems that result from modifying the original Log4j JARs.

[hongwingl]

Thanks for your reply! Apologies, I should be clearer.
In log4j 2.17.1, if I do not use multi release jar, I indeed get the following warning:

sun.reflect.Reflection.getCallerClass(int)` is not supported. This will impact location-based features.

However for 2.24.3, this warning is gone. It just fails silently, with no warning printed. It would make it very difficult to diagnose this issue.