java - Tomcat ClassNotFoundException : org. slf4j.spi.LoggerFactoryBinder 但 slf4j 在库中

Question

我不断收到以下错误:

Failed to instantiate SLF4J LoggerFactory
Reported exception:
java.lang.NoClassDefFoundError: org/slf4j/spi/LoggerFactoryBinder
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:270)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1562)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1420)
        at org.slf4j.LoggerFactory.bind(LoggerFactory.java:129)
        at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:108)
        at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:302)
        at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:276)
        at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:156)
        at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:132)
        at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:274)
        at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:282)
        at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:106)
        at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4830)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5276)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:726)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:702)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:698)
        at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:968)
        at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1742)
        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:744)
Caused by: java.lang.ClassNotFoundException: org.slf4j.spi.LoggerFactoryBinder
        at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
        ... 37 more
21-Jun-2014 17:06:51.352 SEVERE [localhost-startStop-1] org.apache.catalina.core.StandardContext.startInternal Error listenerStart
21-Jun-2014 17:06:51.358 SEVERE [localhost-startStop-1] org.apache.catalina.core.StandardContext.startInternal Context [/spring-app] startup failed due to previous errors
21-Jun-2014 17:06:51.399 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory /media/win/d/coding/servers/tomcat/apache-tomcat-8.0.0-RC5/webapps/docs
21-Jun-2014 17:06:51.829 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory /media/win/d/coding/servers/tomcat/apache-tomcat-8.0.0-RC5/webapps/examples
21-Jun-2014 17:06:53.181 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory /media/win/d/coding/servers/tomcat/apache-tomcat-8.0.0-RC5/webapps/host-manager
21-Jun-2014 17:06:53.575 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory /media/win/d/coding/servers/tomcat/apache-tomcat-8.0.0-RC5/webapps/manager
21-Jun-2014 17:06:53.950 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory /media/win/d/coding/servers/tomcat/apache-tomcat-8.0.0-RC5/webapps/ROOT
21-Jun-2014 17:06:54.324 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["http-nio-8080"]
21-Jun-2014 17:06:54.328 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["ajp-nio-8009"]
21-Jun-2014 17:06:54.329 INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 9393 ms
21-Jun-2014 17:07:14.840 INFO [ContainerBackgroundProcessor[StandardEngine[Catalina]]] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/spring-app]
21-Jun-2014 17:07:44.907 INFO [localhost-startStop-2] org.apache.catalina.startup.HostConfig.deployWAR Deploying web application archive /media/win/d/coding/servers/tomcat/apache-tomcat-8.0.0-RC5/webapps/spring-app.war
Failed to instantiate SLF4J LoggerFactory
Reported exception:
java.lang.NoClassDefFoundError: org/slf4j/spi/LoggerFactoryBinder
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:270)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1562)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1420)
        at org.slf4j.LoggerFactory.bind(LoggerFactory.java:129)
        at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:108)
        at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:302)
        at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:276)
        at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:156)
        at org.apache.commons.logging.impl.SLF4JLogFactory.getInstance(SLF4JLogFactory.java:132)
        at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:274)
        at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:282)
        at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:106)
        at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4830)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5276)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:726)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:702)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:698)
        at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:968)
        at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1742)
        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:744)
Caused by: java.lang.ClassNotFoundException: org.slf4j.spi.LoggerFactoryBinder
        at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
        ... 37 more

这没有意义，因为我确实在web-app/WEB-INF/lib/slf4j 中有org.slf4j.spi.LoggerFactoryBinder -api-1.7.6.jar 这在昨天也有效，但网络应用突然无法启动。

这可能是什么原因造成的？
如何在开始时检查/调试 Tomcat 中 Web 应用程序的类路径？

Answer 1

您说 slf4j API jar 是(曾经)是 Web 应用程序的一部分。我猜你的 slf4j binding jar 已经(曾经)安装在 Tomcat 的 lib 目录或某个这样的地方，它不是 Web 应用程序的私有(private)目录。这似乎应该是使用 Slf4j 的一种自然方式——Web 应用程序自带 API jar，而 tomcat 安装提供了正确的绑定(bind)。不幸的是，这不起作用。

引用Tomcat classloader how-to .当以这种方式部署 Slf4j 时，API jar 是使用 Web 应用程序的私有(private)类加载器加载的，而绑定(bind) jar 是使用“公共(public)”类加载器或其他通用类加载器之一加载的。 webapp classloader中的类可以从common loader加载类，但是common loader中的类不能访问webapp loader。

具体来说，当 API jar 中的类试图加载绑定(bind) jar 中的类时，您的异常会发生，即 org.slf4j.impl.StaticLoggerBinder。您在 Web 应用程序中的代码能够访问 API jar，并且 API jar 能够在绑定(bind) jar 中找到此类。但是，StaticLoggingBinder 引用了返回到 API jar 中的 org.slf4j.spi.LoggerFactoryBinder。绑定(bind) jar 中的类无法访问 webapp 类加载器，因此它无法加载该类，您会得到异常。

不幸的是，唯一直接的解决方案是将 Slf4j API 和绑定(bind) jar 部署在同一个“位置”。它们都应该是 Web 应用程序私有(private)类的一部分，或者都是公共(public) Tomcat 类的一部分。