java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost]] at java.util.concurrent.FutureTask.report(FutureTask.java:122) at java.util.concurrent.FutureTask.get(FutureTask.java:192) at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:941) at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) at org.apache.catalina.core.StandardService.startInternal(StandardService.java:422) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:793) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) at org.apache.catalina.startup.Tomcat.start(Tomcat.java:367) at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:107) at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.<init>(TomcatWebServer.java:86) at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getTomcatWebServer(TomcatServletWebServerFactory.java:409) at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:174) at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:179) at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:152) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:544) at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:395) at org.springframework.boot.SpringApplication.run(SpringApplication.java:327) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1255) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1243) at io.renren.AdminApplication.main(AdminApplication.java:18) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost]] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1421) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1411) 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:748) Caused by: org.apache.catalina.LifecycleException: A child container failed during start at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:949) at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:872) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) ... 6 common frames omitted
启动项目报错
网上查了大部分是说servlet-api冲突了，说是在pom.xml文件中exclusion servlet-api.jar就可以了，但这一步我没有成功。
然后查了jdk中的jar包，发现里面有servlet-api
这个我记得之前是为了解决某个问题，把它拷贝进来的
解决：把servlet-api删掉，重新启动项目就可以了。
小结：确实是servlet-api方面的问题