为什么通过 Spring 加载 log4j2.xml 会为 log4j1 类抛出 NoClassDefFoundError？答案

【问题标题】：Why does loading log4j2.xml via Spring throw a NoClassDefFoundError for a log4j1 class?为什么通过 Spring 加载 log4j2.xml 会为 log4j1 类抛出 NoClassDefFoundError？
【发布时间】：2014-10-09 06:50:02
【问题描述】：

我正在将 Spring 4 Web 应用程序部署到 Tomcat 8，并尝试通过 Spring 加载 log4j 配置 (log4j2.xml)，以便可以将其存储在 WAR 之外。有了这个配置，Spring 在部署期间为 log4j1 类 (org.apache.log4j.xml.DOMConfigurator) 抛出一个 NoClassDefFoundError。但是，如果 Log4j2 在类路径上，它就会正确加载。我的依赖项中没有明确的 logj1 库，只有 log4j2。

Initializing Log4J with Spring? 建议在 web.xml 中配置 log4j。我试过了，但 log4j 根本没有加载，应用程序也没有打印任何日志语句。

Correctly using Log4jConfigurer in Spring 建议在 Tomcat 中配置自定义 log4j 配置文件名，但不是我想要的。给定文件名，我需要从 WAR 外部加载文件。

Spring配置加载log4j2.xml：

<!-- Load Log4j config file via Spring -->
<bean id="log4jInitialization" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
    <property name="targetClass" value="org.springframework.util.Log4jConfigurer"/>
    <property name="targetMethod" value="initLogging"/>
    <property name="arguments">
        <list>
            <value>${log4j.config.location}</value>
            <value>${log4j.refresh.interval}</value>
        </list>
    </property>
</bean>

完整的堆栈跟踪：

 org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'log4jInitialization' defined in ServletContext resource [/WEB-INF/spring/root-context.xml]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: org/apache/log4j/xml/DOMConfigurator
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1553)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:298)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:684)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:760)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:482)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:403)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:306)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:106)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4760)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5184)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:724)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:700)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:714)
    at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:919)
    at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1704)
    at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/xml/DOMConfigurator
    at org.springframework.util.Log4jConfigurer.initLogging(Log4jConfigurer.java:102)
    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.springframework.util.MethodInvoker.invoke(MethodInvoker.java:269)
    at org.springframework.beans.factory.config.MethodInvokingBean.invokeWithTargetException(MethodInvokingBean.java:119)
    at org.springframework.beans.factory.config.MethodInvokingFactoryBean.afterPropertiesSet(MethodInvokingFactoryBean.java:106)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1612)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1549)

【问题讨论】：

标签： java spring logging log4j log4j2

【解决方案1】：

编辑：Log4jConfigurer 不适用于 log4j2，因为它依赖于（仅限 log4j1）DOMConfigurator 类。请从您的弹簧配置中删除它。

改为使用 log4j2 提供的机制来控制配置文件位置：系统属性“log4j.configurationFile”，或者参见 Web 应用程序 log4j2 手册页。

【讨论】：