SpringBoot Bean无法注入的问题 org.springframework.beans.factory.NoSuchBeanDefinitionException Spring

整个项目通过Maven构建，大致结构如下：

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【SpringBoot Bean无法注入的问题 org.springframework.beans.factory.NoSuchBeanDefinitionException】
其中在 screenrecord 有一个Application类

package com.zzz.screenrecord; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.openfeign.EnableFeignClients; /** * @author wang * create on 2020/7/2 */ @EnableDiscoveryClient @EnableFeignClients @SpringBootApplication public class ScreenRecordApplication { public static void main(String[] args) { SpringApplication.run(ScreenRecordApplication.class,args); } }

运行之后总是报错：

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.zzz.screenrecord.mapper.ScreenRecordMapper' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1695) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE] at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1253) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE] at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1207) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE] at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

后来经研究发现，SpringBoot项目的Bean装配默认规则是根据Application类所在的包位置从上往下扫描！
“Application类”是指SpringBoot项目入口类。这个类的位置很关键：
如果Application类所在的包为：com.zzz.screenrecord 则只会扫描 com.zzz.screenrecord 包及其所有的子包，如果service或dao不在 com.zzz.screenrecord包下，则不会被扫描。