Starting Tomcat V8.5 Server at localhost has encountered a problem.

今天使用eclipse中的tomcate8.5釋出工程，一開始沒有問題，但是當我改了一下web.xml以後，再重新啟動時，報以下的錯誤

Starting Tomcat v8.5 Server at localhost has encountered a problem.ServerTomcatv8.5Serveratlocalhostfailedtostart.

檢視控制台，報

資訊:StartingServletEngine:ApacheTomcat/8.5

java.lang.IllegalArgumentException:Servletmappingspecifiesanunknownservletnamestu_Login

atorg.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3109)

atorg.apache.catalina.core.StandardContext.addServletMapping(StandardContext.java:3088)

atorg.apache.catalina.deploy.WebXml.configureContext(WebXml.java:1274)

atorg.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1326)

atorg.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:876)

atorg.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:317)

atorg.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)

atorg.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:89)

atorg.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5061)

atorg.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)

atorg.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1033)

atorg.apache.catalina.core.StandardHost.startInternal(StandardHost.java:774)

atorg.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)

atorg.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1033)

atorg.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:291)

atorg.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)

atorg.apache.catalina.core.StandardService.startInternal(StandardService.java:443)

atorg.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)

atorg.apache.catalina.core.StandardServer.startInternal(StandardServer.java:727)

atorg.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)

atorg.apache.catalina.startup.Catalina.start(Catalina.java:620)

atsun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethod)

atsun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

atjava.lang.reflect.Method.invoke(Method.java:597)

atorg.apache.catalina.startup.Bootstrap.start(Bootstrap.java:303)

atorg.apache.catalina.startup.Bootstrap.main(Bootstrap.java:431)

剛開始以為端口被占用之類的，後來把能關的都關了還是不行，最後重新開機電腦還是不行，後來打開eclipse，clean一下，然後項目上右鍵-->properties-->找到project facets-->在右邊頁籤中找到RunTimes-->選中ApacheTomcat v8.5，然後重新啟動eclipse,成功了！