學習springboot，比着教學視頻做helloworld的例子，視頻裏三下五除二就完事了，結果到我這裏，死活成功不了，網上有說jar衝突的，有說配置不完整的、配置有錯的，但是對於一個小白來說，自己按照他們的步驟去解決太難了，也許他們思路是清晰的，但是他們表述的太籠統了，困擾了兩天，終於找到了正確答案，是java的問題，jre的lib下的ext裏有個servlet-api.jar文件，跟idea自動部署的jar包重複了。
貼下具體錯誤：
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]
at java.util.concurrent.FutureTask.report(FutureTask.java:122) [na:1.8.0_102]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) [na:1.8.0_102]
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:939) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:872) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1419) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409) [tomcat-embed-core-8.5.23.jar:8.5.23]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_102]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_102]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_102]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_102]
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) [tomcat-embed-core-8.5.23.jar:8.5.23]
... 6 common frames omitted
Caused by: org.apache.catalina.LifecycleException: Failed to start component [Pipeline[StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5117) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.23.jar:8.5.23]
... 6 common frames omitted
Caused by: org.apache.catalina.LifecycleException: Failed to start component [org.apache.catalina.authenticator.NonLoginAuthenticator[]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) [tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.core.StandardPipeline.startInternal(StandardPipeline.java:182) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.23.jar:8.5.23]
... 8 common frames omitted
Caused by: java.lang.NoSuchMethodError: javax.servlet.ServletContext.getVirtualServerName()Ljava/lang/String;
at org.apache.catalina.authenticator.AuthenticatorBase.startInternal(AuthenticatorBase.java:1141) ~[tomcat-embed-core-8.5.23.jar:8.5.23]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.23.jar:8.5.23]
... 10 common frames omitted
重複的jar包的路徑爲：你的java路徑下的jre\lib\ext\servlet-api.jar，剪切出來或者刪除都可以。