起因：在解决别的bug的时候，把“application.properties”重命名为“application.yml”，没有用又改回来了。

结果：

项目不加载 application.properties 配置文件!!!

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-02-27 08:28:28.497 ERROR 11936 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'eduChapterController': Lookup method resolution failed; nested exception is java.lang.IllegalStateException: Failed to introspect Class [com.atguigu.eduservice.controller.EduChapterController] from ClassLoader [sun.misc.Launcher$AppClassLoader@18b4aac2]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:287) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineConstructorsFromBeanPostProcessors(AbstractAutowireCapableBeanFactory.java:1286) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1201) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:879) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
	at com.atguigu.eduservice.EduApplication.main(EduApplication.java:18) [classes/:na]
Caused by: java.lang.IllegalStateException: Failed to introspect Class [com.atguigu.eduservice.controller.EduChapterController] from ClassLoader [sun.misc.Launcher$AppClassLoader@18b4aac2]
	at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:477) ~[spring-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.util.ReflectionUtils.doWithLocalMethods(ReflectionUtils.java:318) ~[spring-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:265) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	... 18 common frames omitted
Caused by: java.lang.NoClassDefFoundError: com/atguigu/commonutils/R
	at java.lang.Class.getDeclaredMethods0(Native Method) ~[na:1.8.0_131]
	at java.lang.Class.privateGetDeclaredMethods(Class.java:2701) ~[na:1.8.0_131]
	at java.lang.Class.getDeclaredMethods(Class.java:1975) ~[na:1.8.0_131]
	at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:459) ~[spring-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
	... 20 common frames omitted
Caused by: java.lang.ClassNotFoundException: com.atguigu.commonutils.R
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_131]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_131]
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335) ~[na:1.8.0_131]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_131]
	... 24 common frames omitted

Disconnected from the target VM, address: '127.0.0.1:10210', transport: 'socket'

Process finished with exit code 1

解决方式：
参考：SpringBoot 项目不加载 application.properties 配置文件 - 威威超酷 - 博客园 https://www.cnblogs.com/wwct/p/12258984.html
（感谢大佬！）

yml或者properties文件没有被扫描到,需要在pom文件中<build></build>添加如下.来保证文件都能正常被扫描到并且加载成功.
<!-- 如果不添加此节点mybatis的mapper.xml文件都会被漏掉。 -->
<resources>
    <resource>
        <directory>src/main/java</directory>
        <includes>
            <include>**/*.yml</include>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
        </includes>
        <filtering>false</filtering>
    </resource>
    <resource>
        <directory>src/main/resources</directory>
        <includes>
            <include>**/*.yml</include>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
        </includes>
        <filtering>false</filtering>
    </resource>
</resources>