在学Struts2时，遇到Tomcat报错：Server Tomcat v8.5 Server at localhost failed to start.
console台部分报错信息：
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/struts2Helloworld2]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
... 6 more
Caused by: java.lang.IllegalArgumentException: Filter mapping specifies an unknown filter name [struts2]
错误原因：
web.xml中<filter>和<filter-mapping>中的filter-name不一致。
解决方法：
把<filter>和<filter-mapping>中的filter-name改为一致就好了。