升级log4j至2.20.0后出现org.apache.log4j.PropertyConfigurator类找不到问题

问题 #

在遗留系统代码库中完成以下升级操作：

• 将log4j从1.2.16版本升级至2.20.0版本
• 将Spring Security从4.1.1版本升级至5.2.15版本

已更新的Maven依赖配置如下：

<dependencyManagement>
    <dependencies>
    <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-bom</artifactId>
            <version>2.20.0</version>
            <scope>import</scope>
            <type>pom</type>
        </dependency>
    </dependencies>
</dependencyManagement>
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-core</artifactId>
    <version>5.2.15.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-config</artifactId>
    <version>5.2.15.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-cas</artifactId>
    <version>5.2.15.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.reactivestreams</groupId>
    <artifactId>reactive-streams</artifactId>
    <version>1.0.4</version>
</dependency>

启动应用时抛出NoClassDefFoundError和ClassNotFoundException，具体堆栈信息：

14:46:10,354 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-5) MSC000001: Failed to start service jboss.deployment.unit."cas-ear-2.1.1-SNAPSHOT.ear".POST_MODULE: org.jboss.msc.service.StartException in service jboss.deployment.unit."cas-ear-2.1.1-SNAPSHOT.ear".POST_MODULE: WFLYSRV0153: Failed to process phase POST_MODULE of deployment "cas-ear-2.1.1-SNAPSHOT.ear"
    at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:189)
    at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1739)
    at org.jboss.msc.service.ServiceControllerImpl$StartTask.execute(ServiceControllerImpl.java:1701)
    at org.jboss.msc.service.ServiceControllerImpl$ControllerTask.run(ServiceControllerImpl.java:1559)
    at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
    at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1990)
    at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
    at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1377)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/PropertyConfigurator
    at org.jboss.as.logging.deployments.LoggingConfigDeploymentProcessor.configure(LoggingConfigDeploymentProcessor.java:239)
    at org.jboss.as.logging.deployments.LoggingConfigDeploymentProcessor.processDeployment(LoggingConfigDeploymentProcessor.java:113)
    at org.jboss.as.logging.deployments.LoggingConfigDeploymentProcessor.processDeployment(LoggingConfigDeploymentProcessor.java:141)
    at org.jboss.as.logging.deployments.AbstractLoggingDeploymentProcessor.deploy(AbstractLoggingDeploymentProcessor.java:68)
    at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:182)
    ... 8 more
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.PropertyConfigurator from [Module "org.jboss.as.logging" version 16.0.1.Final from local module loader @604ed9f0 (finder: local module finder @6a4f787b (roots: C:\wildfly-24\cas\wildfly-24.0.1.Final\modules,C:\wildfly-24\cas\wildfly-24.0.1.Final\modules\system\layers\base))]
    at org.jboss.modules.ModuleClassLoader.findClass(ModuleClassLoader.java:255)
    at org.jboss.modules.ConcurrentClassLoader.performLoadClassUnchecked(ConcurrentClassLoader.java:410)
    at org.jboss.modules.ConcurrentClassLoader.performLoadClass(ConcurrentClassLoader.java:398)
    at org.jboss.modules.ConcurrentClassLoader.loadClass(ConcurrentClassLoader.java:116)
    ... 13 more

已完成代码中所有log4j相关导入的更新，且代码库中无旧版log4j的直接调用，需排查并修复该问题。

排查修复方案 #

• 添加log4j1到log4j2的桥接依赖
  WildFly的Logging模块在处理部署时仍尝试加载log4j1.x的API类，需引入桥接依赖让旧API调用转向log4j2实现。在Maven依赖中添加：

  <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-1.2-api</artifactId>
      <version>2.20.0</version>
  </dependency>
  

  该依赖会提供org.apache.log4j.PropertyConfigurator等旧版API类，内部转发到log4j2实现，解决类找不到的问题。

• 修改WildFly部署配置，排除服务器自带的log4j1依赖
  在EAR包的META-INF/jboss-deployment-structure.xml中添加配置，排除服务器模块中的log4j1相关依赖，强制使用应用打包的log4j2：

  <jboss-deployment-structure>
      <deployment>
          <exclude-subsystems>
              <subsystem name="logging"/>
          </exclude-subsystems>
          <exclusions>
              <module name="org.apache.log4j"/>
              <module name="org.jboss.as.logging"/>
          </exclusions>
          <dependencies>
              <module name="org.apache.logging.log4j" export="true"/>
          </dependencies>
      </deployment>
  </jboss-deployment-structure>
  

• 替换旧版log4j配置文件
  检查部署包中是否存在log4j.properties或log4j.xml，WildFly会自动识别这些旧配置文件并尝试用log4j1的加载器处理。将其替换为log4j2的配置文件（如log4j2.xml或log4j2.yaml），并确保配置格式符合log4j2规范。

• 排查并排除传递依赖中的log4j1
  执行Maven命令查看依赖树，找出是否有第三方依赖间接引入了log4j1.x：

  mvn dependency:tree -Dincludes=log4j:log4j
  

  找到后在对应依赖中添加排除配置，例如：

  <dependency>
      <groupId>xxx</groupId>
      <artifactId>xxx</artifactId>
      <exclusions>
          <exclusion>
              <groupId>log4j</groupId>
              <artifactId>log4j</artifactId>
          </exclusion>
      </exclusions>
  </dependency>
  

• 检查服务器启动参数
  查看WildFly的启动脚本或VM参数，是否存在针对log4j1的配置参数（如-Dlog4j.configuration），将其替换为log4j2的参数，例如：

  -Dlog4j.configurationFile=classpath:log4j2.xml
  

内容的提问来源于stack exchange，提问作者190303458