今天用spring5.0做了一个工程，tomcat一直启动报错，
后来去官网查了下。原来5.0只支持jdk8+，我本地是jdk7，所以出现版本不匹配。
严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/ssm-crud]]
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:188)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:943)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:871)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1408)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1398)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/ssm-crud]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:162)
… 6 more
Caused by: java.lang.UnsupportedClassVersionError: org/springframework/web/SpringServletContainerInitializer : Unsupported major.minor version 52.0 (unable to load class org.springframework.web.SpringServletContainerInitializer)
at org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2576)
at org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:859)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1308)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1167)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:278)
at org.apache.catalina.startup.WebappServiceLoader.loadServices(WebappServiceLoader.java:186)
at org.apache.catalina.startup.WebappServiceLoader.load(WebappServiceLoader.java:157)
at org.apache.catalina.startup.ContextConfig.processServletContainerInitializers(ContextConfig.java:1631)
at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1140)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:783)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:307)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:95)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5213)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
… 6 more