Spring 使用 SLF4J代替 Commons Logging 写日志 异常

项目的日志更换成slf4j和logback后，发现项目无法启动。错误提示 Caused by: java.lang.NoClassDefFoundError: Lorg/apache/commons/logging/Log;，如图所示。

Jun 24, 2016 10:18:08 AM org.apache.catalina.core.ContainerBase addChildInternal
SEVERE: ContainerBase.addChild: start:
org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:153)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:899)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:875)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
        at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:1091)
        at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1980)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
        at java.util.concurrent.FutureTask.run(FutureTask.java:262)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NoClassDefFoundError: Lorg/apache/commons/logging/Log;
        at java.lang.Class.getDeclaredFields0(Native Method)
        at java.lang.Class.privateGetDeclaredFields(Class.java:2499)
        at java.lang.Class.getDeclaredFields(Class.java:1811)
        at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:106)
        at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:270)
        at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:139)
        at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:65)
        at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:415)
        at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:892)
        at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:386)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
        at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5472)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
        ... 10 more
Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.Log
        at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1858)
        at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1701)
        ... 24 more

原因是 spring 默认使用 commons logging 写日志，需要桥接工具把日志输入重定向到 slf4j。在项目中添加 commons logging 到 slf4j 的桥接器 jcl-over-slf4j 即可解决该问题。

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>jcl-over-slf4j</artifactId>
</dependency>