log4j - How can I change the default location of log4j2.xml in Java Spring Boot?

Question

Log4j2 is working nicely with Spring Boot through the log4j2.xml configuration file in the root classpath, exactly as the documentation states.

When trying to move this file to a different location though, I'm not able to pass the new location to Spring at startup. From the documentation:

The various logging systems can be activated by including the appropriate libraries on the classpath, and further customized by providing a suitable configuration file in the root of the classpath, or in a location specified by the Spring Environment property logging.config.

I tried setting the new location with a Java system property

java -jar -Dlogging.config="classpath:/config/log4j2.xml" target/app.jar

or using an external application.properties containing the relevant property

logging.config=classpath:/config/log4j2.xml

But I am regularly greeted by the following error message.

ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.

Answer 1

As specified in the Spring reference documentation, the logging.config property cannot be set among the application properties, as they are read after the logging has already been initialised.

The solution is to provide the path to the external logging configuration this way:

java -Dlogging.config='/path/to/log4j2.xml' -jar app-current.jar