Your ApplicationContext is unlikely to start due to a @ComponentScan of the default package

SpringBoot出现下列错误。
Your ApplicationContext is unlikely to start due to a @ComponentScan of the default package
Destroy method on bean with name 'org.springframework.boot.autoconfigure.internalCachingMetadataReaderFactory' threw an exception

或者

Your ApplicationContext is unlikely to start due to a @ComponentScan of the default package
Destroy method on bean with name 'org.springframework.boot.autoconfigure.internalCachingMetadataReaderFactory' threw an exception

或者
ApplicationEventMulticaster not initialized - call 'refresh' before multicasting events via the context: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@4b9e255: startup date [Wed Jul 26 13:37:27 CST 2017]; root of context hierarchy

主要是由于application.java文件没有放在main/java文件夹的原因，因为application.Java 文件不能直接放在main/java文件夹下，必须要建一个包把他放进去
SpringBoot在写启动类的时候如果不使用@ComponentScan指明对象扫描范围，默认指扫描当前启动类所在的包里的对象，如果当前启动类没有包，则在启动时会报错：

Your ApplicationContext is unlikely to start due to a @ComponentScan of the default package错误。

@SpringBootApplication
@ComponentScan(basePackageClasses＝MytestApplication.class)
public class MytestApplication {

public static void main(String[] args){
SpringApplication.run(MytestApplication.class, args);
}
}

@ComponentScan(basePackageClasses＝要扫描类.class所在位置的包)－意思是要扫描哪个类所在的包