springboot org.apache.catalina.LifecycleException: A child container failed during start

springboot org.apache.catalina.LifecycleException: A child container failed during start

严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].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:1128)
	at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.startup.Catalina.start(Catalina.java:675)
	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:483)
	at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322)
	at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:450)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1566)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1556)
	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:745)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1136)
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:782)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)

springboot 启动报了这么一个错，起初一脸懵逼，后来检查发现是因为自己的在二方库jar包中引入了一个servlet-api.jar包

如下图：

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
        </dependency>

在启动时 类路径里面有多个版本servlet-api，导致类冲突

改成下面这样，问题解决：

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <scope>provided</scope>
        </dependency>

scope为 provided代表只编译不运行，没有传递性