ConfigurationClassParser detects @Bean methods in interface hierarchies as well

Issue: SPR-14288

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassParser.java

@@ -303,15 +303,7 @@ class ConfigurationClassParser {
 		}
 
 		// Process default methods on interfaces
-		for (SourceClass ifc : sourceClass.getInterfaces()) {
-			beanMethods = ifc.getMetadata().getAnnotatedMethods(Bean.class.getName());
-			for (MethodMetadata methodMetadata : beanMethods) {
-				if (!methodMetadata.isAbstract()) {
-					// A default method or other concrete method on a Java 8+ interface...
-					configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
-				}
-			}
-		}
+		processInterfaces(configClass, sourceClass);
 
 		// Process superclass, if any
 		if (sourceClass.getMetadata().hasSuperClass()) {
@@ -329,8 +321,6 @@ class ConfigurationClassParser {
 
 	/**
 	 * Register member (nested) classes that happen to be configuration classes themselves.
-	 * @param sourceClass the source class to process
-	 * @throws IOException if there is any problem reading metadata from a member class
 	 */
 	private void processMemberClasses(ConfigurationClass configClass, SourceClass sourceClass) throws IOException {
 		for (SourceClass memberClass : sourceClass.getMemberClasses()) {
@@ -352,6 +342,22 @@ class ConfigurationClassParser {
 		}
 	}
 
+	/**
+	 * Register default methods on interfaces implemented by the configuration class.
+	 */
+	private void processInterfaces(ConfigurationClass configClass, SourceClass sourceClass) throws IOException {
+		for (SourceClass ifc : sourceClass.getInterfaces()) {
+			Set<MethodMetadata> beanMethods = ifc.getMetadata().getAnnotatedMethods(Bean.class.getName());
+			for (MethodMetadata methodMetadata : beanMethods) {
+				if (!methodMetadata.isAbstract()) {
+					// A default method or other concrete method on a Java 8+ interface...
+					configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
+				}
+			}
+			processInterfaces(configClass, ifc);
+		}
+	}
+
 	/**
 	 * Process the given <code>@PropertySource</code> annotation metadata.
 	 * @param propertySource metadata for the <code>@PropertySource</code> annotation found

spring-context/src/test/java/org/springframework/context/annotation/ConfigurationClassPostProcessorTests.java

@@ -1063,17 +1063,27 @@ public class ConfigurationClassPostProcessorTests {
 		}
 	}
 
-	public interface DefaultMethodsConfig {
+	public interface BaseInterface {
 
-		@Bean
-		default ServiceBean serviceBean() {
-			return provider().getServiceBean();
-		}
+		ServiceBean serviceBean();
+	}
+
+	public interface BaseDefaultMethods extends BaseInterface {
 
 		@Bean
 		default ServiceBeanProvider provider() {
 			return new ServiceBeanProvider();
 		}
+
+		@Bean
+		@Override
+		default ServiceBean serviceBean() {
+			return provider().getServiceBean();
+		}
+	}
+
+	public interface DefaultMethodsConfig extends BaseDefaultMethods {
+
 	}
 
 	@Configuration