SpringBoot v2.4.6/2.5.0에서 실행 에러 - No subdirectories found for mandatory directory location 'file:./config/*/'.

SpringBoot v2.4.6/2.5.0에서 빌드 후 실행하면 아래와 같은 에러가 발생한다.

09:50:25.658 [main] ERROR org.springframework.boot.SpringApplication - Application run failed
java.lang.IllegalStateException: No subdirectories found for mandatory directory location 'file:./config/*/'.
at org.springframework.util.Assert.state(Assert.java:76)
at org.springframework.boot.context.config.StandardConfigDataLocationResolver.resolvePatternEmptyDirectories(StandardConfigDataLocationResolver.java:269)
at org.springframework.boot.context.config.StandardConfigDataLocationResolver.resolveEmptyDirectories(StandardConfigDataLocationResolver.java:258)
at org.springframework.boot.context.config.StandardConfigDataLocationResolver.resolveEmptyDirectories(StandardConfigDataLocationResolver.java:249)
at org.springframework.boot.context.config.StandardConfigDataLocationResolver.resolve(StandardConfigDataLocationResolver.java:240)
at org.springframework.boot.context.config.StandardConfigDataLocationResolver.resolve(StandardConfigDataLocationResolver.java:118)
at org.springframework.boot.context.config.ConfigDataLocationResolvers.lambda$resolve$1(ConfigDataLocationResolvers.java:115)
at org.springframework.boot.context.config.ConfigDataLocationResolvers.resolve(ConfigDataLocationResolvers.java:126)
at org.springframework.boot.context.config.ConfigDataLocationResolvers.resolve(ConfigDataLocationResolvers.java:115)
at org.springframework.boot.context.config.ConfigDataLocationResolvers.resolve(ConfigDataLocationResolvers.java:107)
at org.springframework.boot.context.config.ConfigDataImporter.resolve(ConfigDataImporter.java:105)
at org.springframework.boot.context.config.ConfigDataImporter.resolve(ConfigDataImporter.java:97)
at org.springframework.boot.context.config.ConfigDataImporter.resolveAndLoad(ConfigDataImporter.java:85)
at org.springframework.boot.context.config.ConfigDataEnvironmentContributors.withProcessedImports(ConfigDataEnvironmentContributors.java:121)
at org.springframework.boot.context.config.ConfigDataEnvironment.processInitial(ConfigDataEnvironment.java:243)
at org.springframework.boot.context.config.ConfigDataEnvironment.processAndApply(ConfigDataEnvironment.java:230)
at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:102)
at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:94)
at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEnvironmentPreparedEvent(EnvironmentPostProcessorApplicationListener.java:100)
at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEvent(EnvironmentPostProcessorApplicationListener.java:86)
at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:176)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:169)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:143)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:131)
at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:82)
at org.springframework.boot.SpringApplicationRunListeners.lambda$environmentPrepared$2(SpringApplicationRunListeners.java:63)
at java.util.ArrayList.forEach(ArrayList.java:1257)
at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:117)
at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:111)
at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:62)
at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:373)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:331)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1336)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1325)
at com.narusec.httpish.HttpishApplication.main(HttpishApplication.java:12)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49)
at org.springframework.boot.loader.Launcher.launch(Launcher.java:108)
at org.springframework.boot.loader.Launcher.launch(Launcher.java:58)
at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88)

임시 방편으로 아래와 같이 3가지 방법으로 에러를 발생하지 않게 할 수 있다.

1. config 아래에 임의의 subdirectory를 생성한다.
2. 환경변수설정 SPRING_CONFIG_LOCATION=optional:classpath:/,optional:classpath:/config/,optional:file:./,optional:file:./config/
3. java 명령 인자spring.config.locataion=optional:classpath:/,optional:classpath:/config/,optional:file:./,optional:file:./config/