java.lang.ClassNotFoundException：将 log4j 1.2.17 更新到 2.13.0 后的 org.apache.logging.log4j.Logger

Question

我在 Java Eclipse 项目上运行 Tomcat v9.0 服务器。 每次我在服务器上运行我的应用程序时，我都会收到此问题发生的消息：

服务器 Tomcat v9.0 服务器在 localhost 启动失败。

这是我收到的控制台消息：

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"]

我认为我的记录器有问题。 我最初使用的是 log4j v1.2.17，然后我想升级到最新版本的 log4j，即 v2.13.0。

这是我的log4j2.properties file样子：

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

此服务器错误的根本原因是什么，我该如何解决？ 谢谢你。

Answer 1

弄清楚了！ BalusC 是正确的。 Tomcat 不需要记录器来工作，因此，我删除了所有记录器引用并且 tomcat 工作。 然后，要更新，我必须在线手动下载 log4j jar，然后将它们粘贴到我的类路径中。 此外，当从log4j迁移到log4j2时，我必须在使用记录器的每个类中使用不同类型的记录器导入和实例化，如下所示：

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

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

我还必须在位于/src/main/resources/log4j2.xml的 xml 文件中配置 log4j2，如下所示：

<?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>

在我的 pom.xml 中，我还确保我有正确的 log4j2 依赖项和 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>

完成所有这些后，我就能够在 Tomcat v9.0 服务器上运行我的项目并成功登录到控制台和 log.txt 文件。