Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost]] Caused by: org.apache.catalina.LifecycleException: A child container failed during start
在tomcat7:run时，报错如上。是因为servlet的依赖冲突，忘记加上这一句了：
provided
屡试不爽的solution。
最后这样就可以成功启动了：
