【web】Server Tomcat v9.0 Server at localhost failed to start.

报错原因：

Caused by: java.lang.IllegalArgumentException: More than one fragment with the name [spring_web] was found. This is not legal with relative ordering. See section 8.2.2 2c of the Servlet specification for details. Consider using absolute ordering.
 at org.apache.tomcat.util.descriptor.web.WebXml.orderWebFragments(WebXml.java:2260)
 at org.apache.tomcat.util.descriptor.web.WebXml.orderWebFragments(WebXml.java:2218)
 at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1133)
 at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:774)
 at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:301)
 at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:123)
 at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5056)
 at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
 ... 27 more
<absolut

解决办法：
在web.xml加一个标签：