先说结论

SpringBoot Application共支持6种事件监听，按顺序分别是：

ApplicationStartingEvent：在Spring最开始启动的时候触发

ApplicationEnvironmentPreparedEvent：在Spring已经准备好上下文但是上下文尚未创建的时候触发

ApplicationPreparedEvent：在Bean定义加载之后、刷新上下文之前触发

ApplicationStartedEvent：在刷新上下文之后、调用application命令之前触发

ApplicationReadyEvent：在调用applicaiton命令之后触发

ApplicationFailedEvent：在启动Spring发生异常时触发

另外：

ApplicationRunner和CommandLineRunner的执行在第五步和第六步之间

Bean的创建在第三步和第四步之间

在启动类中，执行SpringApplication.run()方法后的代码，会在第六步后执行

再上代码：

ApplicationStartingEvent

public class ApplicationStartingEventListener implements ApplicationListener {

@Override

public void onApplicationEvent(ApplicationStartingEvent applicationStartingEvent) {

System.out.println("============>>>>> applicationStartingEvent is trigged");

System.out.println(applicationStartingEvent.getTimestamp());

System.out.println("============>>>>> End");

}

}

ApplicationEnvironmentPreparedEvent

public class ApplicationEnvironmentPreparedEventListener implements ApplicationListener {

@Override

public void onApplicationEvent(ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {

System.out.println("============>>>>> ApplicationEnvironmentPreparedEvent is trigged");

System.out.println(applicationEnvironmentPreparedEvent.getTimestamp());

System.out.println("============>>>>> End");

}

}

ApplicationEnvironmentPreparedEvent

ApplicationPreparedEvent

public class ApplicationPreparedEventListener implements ApplicationListener {

@Override

public void onApplicationEvent(ApplicationPreparedEvent applicationPreparedEvent) {

System.out.println("============>>>>> applicationPreparedEvent is trigged");

System.out.println(applicationPreparedEvent.getTimestamp());

Syste