Getting this error: "Could not initialize class org.apache.logging.log4j.LogManager"

Question

I have included all the necessary log4j jar files and I don't understand why I'm still getting this error.

package in.gstzen.einvoice;
import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;

public class Log4jExample {

    private static Logger logger = LogManager.getLogger(Log4jExample.class);

    public static void main(String[] args) throws Exception {

        System.out.println("Hello World!\n");
        logger.debug("Log4jExample: A Sample Debug Message");
        logger.info("Log4jExample: A Sample Info  Message");
        logger.warn("Log4jExample: A Sample Warn  Message");
        logger.error("Log4jExample: A Sample Error Message");
        logger.fatal("Log4jExample: A Sample Fatal Message");
        System.out.println("Completed...");
    }
}

Answer 1

This looks like a conflict between log4j versions 1 and 2. Your class is importing version 1 classes, but the error message is in response to the spring framework not finding the jar files for version 2 classes. You want to use one version or the other.

Version 1 is going to have classes with packages org.apache.log4j.x.
The jar will be called log4j-1.x.x

Version 2 is going to have classes with packages like org.apache.logging.log4j.x.
The jars will be named log4j-core-2.x.x and an the implementation like log4j-slf4j18-impl-2.x.x.

See this migration helper: https://logging.apache.org/log4j/2.x/manual/migration.html

Note: If your classpath includes both the version 1 and version 2 jars resolution of the actual classes used can be somewhat random (and problematic).

Answer 2

Please list the jars you added.

See here: https://www.cwiki.us/questions/13469089/could-not-initialize-class-org.apache.logging.log4j.logmanager