Support @Import on interfaces

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

@@ -98,6 +98,7 @@
  * @author Phillip Webb
  * @author Sam Brannen
  * @author Stephane Nicoll
+ * @author Daeho Kwon
  * @since 3.0
  * @see ConfigurationClassBeanDefinitionReader
  */
@@ -549,6 +550,9 @@ private Set<SourceClass> getImports(SourceClass sourceClass) throws IOException
 	 * <p>For example, it is common for a {@code @Configuration} class to declare direct
 	 * {@code @Import}s in addition to meta-imports originating from an {@code @Enable}
 	 * annotation.
+	 * <p>In addition, {@code @Import} annotations declared on interfaces implemented by
+	 * the configuration class are also considered. This allows imports to be triggered
+	 * indirectly via marker interfaces or shared base interfaces.
 	 * @param sourceClass the class to search
 	 * @param imports the imports collected so far
 	 * @param visited used to track visited classes to prevent infinite recursion
@@ -565,6 +569,10 @@ private void collectImports(SourceClass sourceClass, Set<SourceClass> imports, S
 				}
 			}
 			imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), "value"));
+
+			for (SourceClass ifc : sourceClass.getInterfaces()) {
+				collectImports(ifc, imports, visited);
+			}
 		}
 	}
 

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

@@ -62,6 +62,7 @@
  *
  * @author Phillip Webb
  * @author Stephane Nicoll
+ * @author Daeho Kwon
  */
 @SuppressWarnings("resource")
 public class ImportSelectorTests {
@@ -203,6 +204,38 @@ void invokeAwareMethodsInImportGroup() {
 		assertThat(TestImportGroup.environment).isEqualTo(context.getEnvironment());
 	}
 
+	@Test
+	void importAnnotationOnImplementedInterfaceIsRespected() {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		context.register(InterfaceBasedConfig.class);
+		context.refresh();
+
+		assertThat(context.getBean(ImportedConfig.class)).isNotNull();
+		assertThat(context.getBean(ImportedBean.class)).isNotNull();
+		assertThat(context.getBean(ImportedBean.class).name()).isEqualTo("imported");
+	}
+
+	@Import(ImportedConfig.class)
+	interface ConfigImportMarker {
+	}
+
+	@Configuration
+	static class InterfaceBasedConfig implements ConfigImportMarker {
+	}
+
+	static class ImportedBean {
+		String name() {
+			return "imported";
+		}
+	}
+
+	@Configuration
+	static class ImportedConfig {
+		@Bean
+		ImportedBean importedBean() {
+			return new ImportedBean();
+		}
+	}
 
 	@Configuration
 	@Import(SampleImportSelector.class)