我正在尝试安装 YouTrack。我安装了 Tomcat 7 并且工作正常（我能够加载 localhost:8080）。现在我正在尝试部署 YouTrack。我按照他们网站上的说明进行操作：
在 Tomcat servlet 容器中部署 youtrack-xx.war：
如果您运行 Tomcat（例如作为 Windows 服务），请在部署 YouTrack 之前停止 Tomcat 实例。
保存
youtrack-xx.war在$TOMCAT_HOME$/webapps目录中。youtrack-xx.war部署前根据需要重命名文件。在进一步的示例中，我们假设 YouTrack servlet 名称设置为youtrack.war。启动 Apache Tomcat 并检查 YouTrack 是否设置正确且可用（在 Web 浏览器中导航到
http://yourserver:<Tomcat port>/youtrack）。
在第 3 步。我无法访问 YouTrack。我得到一个 404。如果我去 Tomcat 的管理站点，它说 YouTrack 的运行状态为 false。如果我单击开始，它将显示以下错误消息：
FAIL - Application at context path /youtrack could not be started
FAIL - Encountered exception org.apache.catalina.LifecycleException:
Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/youtrack]]
我看了看，logs/catalina.out这是完整的错误：
Information: Deploying web application directory /usr/local/apache-tomcat-7.0.50/webapps/youtrack
Feb 02, 2014 3:19:26 PM org.apache.catalina.core.ContainerBase addChildInternal
Schwerwiegend: ContainerBase.addChild: start:
org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/youtrack]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:634)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1230)
at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1876)
at java.util.concurrent.Executors$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.NoClassDefFoundError: org/apache/log4j/xml/DOMConfigurator
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2397)
at java.lang.Class.getDeclaredFields(Class.java:1806)
at org.apache.catalina.util.Introspection.getDeclaredFields(Introspection.java:106)
at org.apache.catalina.startup.WebAnnotationSet.loadFieldsAnnotation(WebAnnotationSet.java:263)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:142)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:67)
at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:407)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:883)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:378)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5343)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 10 more
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.xml.DOMConfigurator
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1702)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
... 24 more
Feb 02, 2014 3:19:26 PM org.apache.catalina.startup.HostConfig deployDirectory
Schwerwiegend: Error deploying web application directory /usr/local/apache-tomcat-7.0.50/webapps/youtrack
java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/youtrack]]
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:904)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:634)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1230)
at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1876)
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)
看起来有些类丢失了，但错误中引用的类确实存在：
$TOMCAT$/webapps/youtrack/org/apache/log4j/xml：
