ApplicationStartedEvent cannot be cast to ApplicationEnvironmentPreparedEvent

SLF4J: Actual binding is of type [ch.qos.logback.classic.util.ContextSelectorStaticBinder]
Exception in thread "main" java.lang.ClassCastException: org.springframework.boot.context.event.ApplicationStartedEvent cannot be cast to org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent
    at org.springframework.boot.context.config.AnsiOutputApplicationListener.onApplicationEvent(AnsiOutputApplicationListener.java:34)
    at org.springframework.context.event.SimpleApplicationEventMulticaster$1.run(SimpleApplicationEventMulticaster.java:78)
    at org.springframework.core.task.SyncTaskExecutor.execute(SyncTaskExecutor.java:50)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:76)
    at org.springframework.boot.context.event.EventPublishingRunListener.started(EventPublishingRunListener.java:67)
    at org.springframework.boot.SpringApplicationRunListeners.started(SpringApplicationRunListeners.java:48)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:305)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1187)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1176)
    at hello.MainController.main(MainController.java:14)

原因：SpringBoot版本问题

排查方法

通过mvn依赖树分析，查看具体的依赖是否有 spring 2.5.6

排除掉对应的包即可：

<exclusions>
  <exclusion>
     <groupId>org.springframework</groupId>
     <artifactId>spring</artifactId>
  </exclusion>
</exclusions>