上周做系统上线时，在tomcat的webapps目录下又添加了一个项目mds.war，war正常部署后，通过浏览器不能正常访问，查看tomcat的log，发现如下报错信息：
16-Apr-2015 08:58:25.937 SEVERE [localhost-startStop-1] org.apache.catalina.core.StandardContext.listenerStart Exception sending context initialized event to listener instance of class org.springframework.web.util.Log4jConfigListener java.lang.IllegalStateException: Web app root system property already set to different value: 'webapp.root' = [/data/tomcat/webapps/bocode] instead of [/data/tomcat/webapps/httpjson] - Choose unique values for the 'webAppRootKey' context-param in your web.xml files! at org.springframework.web.util.WebUtils.setWebAppRootSystemProperty(WebUtils.java:144) at org.springframework.web.util.Log4jWebConfigurer.initLogging(Log4jWebConfigurer.java:117) at org.springframework.web.util.Log4jConfigListener.contextInitialized(Log4jConfigListener.java:45) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4750) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5170) 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:697) 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(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745)
分析上述报错信息：Web app root system property already set to different value
web.xml中webAppRootKey
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1、 web.xml配置 <context-param> <param-name>webAppRootKey</param-name> <param-value>webapp.root</param-value> </context-param>
"webapp.root"这个字符串可以随便写任何字符串。如果不配置默认值是"webapp.root"。
可以用System.getProperty("webapp.root")来动态获项目的运行路径。
一般返回结果例如：/datatomcat/webapps/项目名
2、解决以下报错
部署在同一容器中的Web项目，要配置不同的<param-value>，不能重复，否则报类似下面的错误:
Web app root system property already set to different value: Web app root system property already set to different value: 'webapp.root' = [/data/tomcat/webapps/bocode] instead of [/data/tomcat/webapps/httpjson] - Choose unique values
for the 'webAppRootKey' context-param in your web.xml files!
意思是“webapp.root”这个key已经指向了项目1，不可以再指向项目2.
解决方法如下： ### app1: <context-param> <param-name>webAppRootKey</param-name> <param-value>app1.root</param-value> </context-param> ### app2: <context-param> <param-name>webAppRootKey</param-name> <param-value>app2.roo
参考文章： http://elf8848.iteye.com/blog/2008595
http://yzxqml.iteye.com/blog/1761540
http://www.thinksaas.cn/group/topic/328055/
