まぁこんな事やる人居ないと思うのだけど。遭遇したのでメモを残しておく。

現象

まずエントリーポイントのクラスを作る。

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

@EnableAutoConfigurationを付与するクラスを作成する。

@EnableAutoConfiguration
@Configuration
public class SuperClass {
}

上のクラスを継承するが@EnableAutoConfigurationは付与しない。

@Configuration
public class SubClass extends SuperClass {
}

すると以下のようなSubClassにEnableAutoConfigurationが必要なのでは？　という実行時エラーになる。つければエラーは消える。

java.lang.IllegalArgumentException: No auto-configuration attributes found. Is hogehoge.SubClass annotated with EnableAutoConfiguration?
    at org.springframework.util.Assert.notNull(Assert.java:219) ~[spring-core-5.3.9.jar:5.3.9]
    at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector.getAttributes(AutoConfigurationImportSelector.java:155) ~[spring-boot-autoconfigure-2.5.4.jar:2.5.4]
    at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector.getAutoConfigurationEntry(AutoConfigurationImportSelector.java:122) ~[spring-boot-autoconfigure-2.5.4.jar:2.5.4]
    at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector$AutoConfigurationGroup.process(AutoConfigurationImportSelector.java:434) ~[spring-boot-autoconfigure-2.5.4.jar:2.5.4]
    at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorGrouping.getImports(ConfigurationClassParser.java:879) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorGroupingHandler.processGroupImports(ConfigurationClassParser.java:809) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorHandler.process(ConfigurationClassParser.java:780) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:193) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:331) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:247) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:311) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:112) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:746) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:564) ~[spring-context-5.3.9.jar:5.3.9]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:754) ~[spring-boot-2.5.4.jar:2.5.4]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:434) ~[spring-boot-2.5.4.jar:2.5.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:338) ~[spring-boot-2.5.4.jar:2.5.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1343) ~[spring-boot-2.5.4.jar:2.5.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1332) ~[spring-boot-2.5.4.jar:2.5.4]
    at zgradletest.enablesuper.Main.main(Main.java:9) ~[main/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-2.5.4.jar:2.5.4]

感想

ざっくりソースを見るとサブクラスもEnableAutoConfiguration対象として処理される。このアノテーションの属性を取得しようとするが、そもそもアノテーションが付与されてないのでエラーになる。