Web app root system property already set to different value: 'webapp.root'

java.lang.IllegalStateException: Web app root system property already set to different value: 'webapp.root' = [....\tmp1\wtpwebapps\workreport\] instead of [.....\wtpwebapps\ApprovalFront\] 
- Choose unique values for the 'webAppRootKey' context-param in your web.xml files!
    at org.springframework.web.util.WebUtils.setWebAppRootSystemProperty(WebUtils.java:150)
    at org.springframework.web.util.Log4jWebConfigurer.initLogging(Log4jWebConfigurer.java:116)
    at org.springframework.web.util.Log4jConfigListener.contextInitialized(Log4jConfigListener.java:45)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5016)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5528)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1575)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1565)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
    at java.util.concurrent.FutureTask.run(FutureTask.java:166)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:722)

Tomcat发布多个项目时抛的webAppRootKey错误,  原因是部署在同一容器中的Web项目，定义了相同的webAppRootKey或者都没有定义

解决办法：需要为每个web都定义一个webAppRootKey

 <!--app1中的web.xml-->
<context-param>
    <param-name>webAppRootKey</param-name>
    <param-value>app1.root</param-value>
</context-param>

<!--app2中的web.xml-->
<context-param>
    <param-name>webAppRootKey</param-name>
    <param-value>app2.root</param-value>
</context-param>