java.lang.ClassNotFoundException: org.apache.logging.log4j.Logger after updating log4j 1.2.17 to 2.13.0

Question

I am running Tomcat v9.0 server on a Java Eclipse project. Each time I run my application on the server I get this Problem Occured message:

Server Tomcat v9.0 Server at localhost failed to start.

This is the Console message that I get:

Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server version name:   Apache Tomcat/9.0.30
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server built:          Dec 7 2019 16:42:04 UTC
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server version number: 9.0.30.0
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: OS Name:               Windows 10
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: OS Version:            10.0
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Architecture:          amd64
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Java Home:             C:\Program Files\Java\jre1.8.0_231
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: JVM Version:           1.8.0_231-b11
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: JVM Vendor:            Oracle Corporation
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: CATALINA_BASE:         C:\Users\msoph\Documents\Revature-Projects\.metadata\.plugins\org.eclipse.wst.server.core\tmp0
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: CATALINA_HOME:         C:\Users\msoph\Desktop\apache-tomcat-9.0.30\apache-tomcat-9.0.30
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dcatalina.base=C:\Users\msoph\Documents\Revature-Projects\.metadata\.plugins\org.eclipse.wst.server.core\tmp0
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dcatalina.home=C:\Users\msoph\Desktop\apache-tomcat-9.0.30\apache-tomcat-9.0.30
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dwtp.deploy=C:\Users\msoph\Documents\Revature-Projects\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Djava.endorsed.dirs=C:\Users\msoph\Desktop\apache-tomcat-9.0.30\apache-tomcat-9.0.30\endorsed
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dfile.encoding=Cp1252
Jan 02, 2020 11:21:18 AM org.apache.catalina.core.AprLifecycleListener lifecycleEvent
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: [C:\Program Files\Java\jre1.8.0_231\bin;C:\WINDOWS\Sun\Java\bin;C:\WINDOWS\system32;C:\WINDOWS;C:/Program Files/Java/jre1.8.0_231/bin/server;C:/Program Files/Java/jre1.8.0_231/bin;C:/Program Files/Java/jre1.8.0_231/lib/amd64;C:\Program Files (x86)\Common Files\Oracle\Java\javapath;C:\Program Files\Java\jdk-13.0.1\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\WINDOWS\System32\OpenSSH\;C:\Program Files\Intel\WiFi\bin\;C:\Program Files\Common Files\Intel\WirelessCommon\;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Git\cmd;C:\ProgramData\chocolatey\bin;C:\ProgramData\chocolatey\lib\maven\apache-maven-3.6.2\bin;C:\Program Files\PostgreSQL\12\bin;C:\Program Files\nodejs\;C:\Users\msoph\AppData\Local\Microsoft\WindowsApps;C:\Users\msoph\AppData\Local\Programs\Microsoft VS Code\bin;C:\Program Files\Java\jdk1.8.0_231\bin;C:\Users\msoph\AppData\Roaming\npm;C:\Users\msoph\Desktop\sts4Release;;.]
Jan 02, 2020 11:21:18 AM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-nio-8080"]
Jan 02, 2020 11:21:18 AM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-nio-8009"]
Jan 02, 2020 11:21:18 AM org.apache.catalina.startup.Catalina load
INFO: Server initialization in [798] milliseconds
Jan 02, 2020 11:21:18 AM org.apache.catalina.core.StandardService startInternal
INFO: Starting service [Catalina]
Jan 02, 2020 11:21:18 AM org.apache.catalina.core.StandardEngine startInternal
INFO: Starting Servlet engine: [Apache Tomcat/9.0.30]
Jan 02, 2020 11:21:19 AM org.apache.catalina.core.ContainerBase startInternal
SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/project-1]]
    at java.util.concurrent.FutureTask.report(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:916)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:841)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:421)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:930)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:633)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:343)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:474)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/project-1]]
    at org.apache.catalina.util.LifecycleBase.handleSubClassException(LifecycleBase.java:440)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:198)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909)
    ... 21 more
Caused by: java.lang.NoClassDefFoundError: Lorg/apache/logging/log4j/Logger;
    at java.lang.Class.getDeclaredFields0(Native Method)
    at java.lang.Class.privateGetDeclaredFields(Unknown Source)
    at java.lang.Class.getDeclaredFields(Unknown Source)
    at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:110)
    at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:269)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:137)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:69)
    at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:330)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:777)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:301)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:123)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5051)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    ... 27 more
Caused by: java.lang.ClassNotFoundException: org.apache.logging.log4j.Logger
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1365)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1188)
    ... 40 more

Jan 02, 2020 11:21:19 AM org.apache.catalina.core.ContainerBase startInternal
SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: A child container failed during start
    at java.util.concurrent.FutureTask.report(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:916)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:421)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:930)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:633)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:343)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:474)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:928)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:841)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909)
    ... 13 more
Caused by: java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/project-1]]
    at java.util.concurrent.FutureTask.report(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:916)
    ... 21 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/project-1]]
    at org.apache.catalina.util.LifecycleBase.handleSubClassException(LifecycleBase.java:440)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:198)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909)
    ... 21 more
Caused by: java.lang.NoClassDefFoundError: Lorg/apache/logging/log4j/Logger;
    at java.lang.Class.getDeclaredFields0(Native Method)
    at java.lang.Class.privateGetDeclaredFields(Unknown Source)
    at java.lang.Class.getDeclaredFields(Unknown Source)
    at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:110)
    at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:269)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:137)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:69)
    at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:330)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:777)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:301)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:123)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5051)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    ... 27 more
Caused by: java.lang.ClassNotFoundException: org.apache.logging.log4j.Logger
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1365)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1188)
    ... 40 more

Jan 02, 2020 11:21:19 AM org.apache.catalina.startup.Catalina start
SEVERE: The required Server component failed to start so Tomcat is unable to start.
org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:928)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:421)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:930)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:633)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:343)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:474)
Caused by: java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: A child container failed during start
    at java.util.concurrent.FutureTask.report(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:916)
    ... 13 more
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:928)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:841)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909)
    ... 13 more
Caused by: java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/project-1]]
    at java.util.concurrent.FutureTask.report(Unknown Source)
    at java.util.concurrent.FutureTask.get(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:916)
    ... 21 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/project-1]]
    at org.apache.catalina.util.LifecycleBase.handleSubClassException(LifecycleBase.java:440)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:198)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
    at java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:909)
    ... 21 more
Caused by: java.lang.NoClassDefFoundError: Lorg/apache/logging/log4j/Logger;
    at java.lang.Class.getDeclaredFields0(Native Method)
    at java.lang.Class.privateGetDeclaredFields(Unknown Source)
    at java.lang.Class.getDeclaredFields(Unknown Source)
    at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:110)
    at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:269)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:137)
    at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:69)
    at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:330)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:777)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:301)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:123)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5051)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    ... 27 more
Caused by: java.lang.ClassNotFoundException: org.apache.logging.log4j.Logger
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1365)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1188)
    ... 40 more

Jan 02, 2020 11:21:19 AM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["http-nio-8080"]
Jan 02, 2020 11:21:19 AM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["ajp-nio-8009"]
Jan 02, 2020 11:21:19 AM org.apache.catalina.core.StandardService stopInternal
INFO: Stopping service [Catalina]
Jan 02, 2020 11:21:19 AM org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["http-nio-8080"]
Jan 02, 2020 11:21:19 AM org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["ajp-nio-8009"]

I assume that there is an issue with my logger. I was originally using log4j v1.2.17 and then I thought to upgrade to the most recent version of log4j which is v2.13.0.

This is what my log4j2.properties file looks like:

status = error
name = PropertiesConfig

#Make sure to change log file path as per your need
property.filename = C:\\Users\\msoph\\Documents\\Revature-Projects\\project-1\\logs\\log.txt
filters = threshold

filter.threshold.type = ThresholdFilter
filter.threshold.level = debug

appenders = rolling

appender.rolling.type = RollingFile
appender.rolling.name = RollingFile
appender.rolling.fileName = ${filename}
appender.rolling.filePattern = debug-backup-%d{MM-dd-yy-HH-mm-ss}-%i.log.gz
appender.rolling.layout.type = PatternLayout
appender.rolling.layout.pattern = %d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n
appender.rolling.policies.type = Policies
appender.rolling.policies.time.type = TimeBasedTriggeringPolicy
appender.rolling.policies.time.interval = 1
appender.rolling.policies.time.modulate = true
appender.rolling.policies.size.type = SizeBasedTriggeringPolicy
appender.rolling.policies.size.size=10MB
appender.rolling.strategy.type = DefaultRolloverStrategy
appender.rolling.strategy.max = 20

loggers = rolling

#package structure

logger.rolling.name = com.revature
logger.rolling.level = debug
logger.rolling.additivity = false
logger.rolling.appenderRef.rolling.ref = RollingFile

What is the root cause of this Server error, and how can I fix this? Thank You.

Answer 1

Figured it out! BalusC was correct. Tomcat did not require a logger to work, so, I removed all logger references and tomcat worked. Then, to update, I had to manually download the log4j jars online and then paste them into my classpath. Also, when migrating to log4j2 from log4j, I had to use a different type of logger import and instantiation in each of the classes where I used a logger, as follows:

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

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

I also had to configure log4j2 in an xml file, located in /src/main/resources/log4j2.xml as follows:

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="WARN">
  <appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>

    <File name="log" fileName="logs//log.txt">
        <PatternLayout pattern="%d{yyyy-mm-dd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </File>             
  </appenders>

  <loggers>     
    <root level="DEBUG">
      <appender-ref ref="Console"/>
      <appender-ref ref="log"/>
    </root>    
  </loggers>
</configuration>

In my pom.xml, I also made sure that I had the proper log4j2 dependencies and Maven > Update Project

        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-api -->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.13.0</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.13.0</version>
    </dependency>

Once all of this was done, I was able to run my project on the Tomcat v9.0 server and log successfully to both console and a log.txt file.

Answer 2

I'm using Maven, but I also encountered this error while migrating from log4j 1.x to log4j 2.x and realized I still had some code that only worked with 1.x. But instead of refactoring code I added this dependency to my pom.xml in order to maintain compatibility.

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-1.2-api</artifactId>
    <version>2.17.1</version>
</dependency>