Restored registration of nested component classes (even without factory methods)

Issue: SPR-10865
Issue: SPR-10970

Author: jhoeller

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

@@ -28,11 +28,13 @@
 import org.springframework.core.type.StandardAnnotationMetadata;
 import org.springframework.core.type.classreading.MetadataReader;
 import org.springframework.core.type.classreading.MetadataReaderFactory;
+import org.springframework.stereotype.Component;
 
 /**
  * Utilities for processing @{@link Configuration} classes.
  *
  * @author Chris Beams
+ * @author Juergen Hoeller
  * @since 3.1
  */
 abstract class ConfigurationClassUtils {
@@ -48,8 +50,9 @@ abstract class ConfigurationClassUtils {
 
 
 	/**
-	 * Check whether the given bean definition is a candidate for a configuration class,
-	 * and mark it accordingly.
+	 * Check whether the given bean definition is a candidate for a configuration class
+	 * (or a nested component class declared within a configuration/component class,
+	 * to be auto-registered as well), and mark it accordingly.
 	 * @param beanDef the bean definition to check
 	 * @param metadataReaderFactory the current factory in use by the caller
 	 * @return whether the candidate qualifies as (any kind of) configuration class
@@ -92,22 +95,45 @@ else if (isLiteConfigurationCandidate(metadata)) {
 		return false;
 	}
 
+	/**
+	 * Check the given metadata for a configuration class candidate
+	 * (or nested component class declared within a configuration/component class).
+	 * @param metadata the metadata of the annotated class
+	 * @return {@code true} if the given class is to be registered as a
+	 * reflection-detected bean definition; {@code false} otherwise
+	 */
 	public static boolean isConfigurationCandidate(AnnotationMetadata metadata) {
 		return (isFullConfigurationCandidate(metadata) || isLiteConfigurationCandidate(metadata));
 	}
 
+	/**
+	 * Check the given metadata for a full configuration class candidate
+	 * (i.e. a class annotated with {@code @Configuration}).
+	 * @param metadata the metadata of the annotated class
+	 * @return {@code true} if the given class is to be processed as a full
+	 * configuration class, including cross-method call interception
+	 */
 	public static boolean isFullConfigurationCandidate(AnnotationMetadata metadata) {
 		return metadata.isAnnotated(Configuration.class.getName());
 	}
 
+	/**
+	 * Check the given metadata for a lite configuration class candidate
+	 * (i.e. a class annotated with {@code @Component} or just having
+	 * {@code @Import} declarations or {@code @Bean methods}).
+	 * @param metadata the metadata of the annotated class
+	 * @return {@code true} if the given class is to be processed as a lite
+	 * configuration class, just registering it and scanning it for {@code @Bean} methods
+	 */
 	public static boolean isLiteConfigurationCandidate(AnnotationMetadata metadata) {
 		// Do not consider an interface or an annotation...
-		return (!metadata.isInterface() && (
+		return (!metadata.isInterface() && (metadata.isAnnotated(Component.class.getName()) ||
 				metadata.isAnnotated(Import.class.getName()) || metadata.hasAnnotatedMethods(Bean.class.getName())));
 	}
 
 	/**
-	 * Determine whether the given bean definition indicates a full @Configuration class.
+	 * Determine whether the given bean definition indicates a full {@code @Configuration}
+	 * class, through checking {@link #checkConfigurationClassCandidate}'s metadata marker.
 	 */
 	public static boolean isFullConfigurationClass(BeanDefinition beanDef) {
 		return CONFIGURATION_CLASS_FULL.equals(beanDef.getAttribute(CONFIGURATION_CLASS_ATTRIBUTE));

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

@@ -16,19 +16,20 @@
 
 package org.springframework.context.annotation;
 
-import static org.hamcrest.CoreMatchers.is;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertThat;
-
 import org.junit.Test;
 
+import org.springframework.stereotype.Component;
 import org.springframework.tests.sample.beans.TestBean;
 
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
 /**
  * Tests ensuring that nested static @Configuration classes are automatically detected
  * and registered without the need for explicit registration or @Import. See SPR-8186.
  *
  * @author Chris Beams
+ * @author Juergen Hoeller
  * @since 3.1
  */
 public class NestedConfigurationClassTests {
@@ -89,6 +90,36 @@ public void twoLevelsDeepWithInheritance() {
 		assertThat(ctx.getBean("overrideBean", TestBean.class).getName(), is("override-s1"));
 	}
 
+	@Test
+	public void twoLevelsInLiteMode() {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.register(L0ConfigLight.class);
+		ctx.refresh();
+
+		ctx.getBean(L0ConfigLight.class);
+		ctx.getBean("l0Bean");
+
+		ctx.getBean(L0ConfigLight.L1ConfigLight.class);
+		ctx.getBean("l1Bean");
+
+		ctx.getBean(L0ConfigLight.L1ConfigLight.L2ConfigLight.class);
+		ctx.getBean("l2Bean");
+
+		// ensure that override order is correct
+		assertThat(ctx.getBean("overrideBean", TestBean.class).getName(), is("override-l0"));
+	}
+
+	@Test
+	public void twoLevelsWithNoBeanMethods() {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.register(L0ConfigEmpty.class);
+		ctx.refresh();
+
+		ctx.getBean(L0ConfigEmpty.class);
+		ctx.getBean(L0ConfigEmpty.L1ConfigEmpty.class);
+		ctx.getBean(L0ConfigEmpty.L1ConfigEmpty.L2ConfigEmpty.class);
+	}
+
 
 	@Configuration
 	static class L0Config {
@@ -130,6 +161,59 @@ public TestBean overrideBean() {
 	}
 
 
+	@Component
+	static class L0ConfigLight {
+		@Bean
+		public TestBean l0Bean() {
+			return new TestBean("l0");
+		}
+
+		@Bean
+		public TestBean overrideBean() {
+			return new TestBean("override-l0");
+		}
+
+		@Component
+		static class L1ConfigLight {
+			@Bean
+			public TestBean l1Bean() {
+				return new TestBean("l1");
+			}
+
+			@Bean
+			public TestBean overrideBean() {
+				return new TestBean("override-l1");
+			}
+
+			@Component
+			protected static class L2ConfigLight {
+				@Bean
+				public TestBean l2Bean() {
+					return new TestBean("l2");
+				}
+
+				@Bean
+				public TestBean overrideBean() {
+					return new TestBean("override-l2");
+				}
+			}
+		}
+	}
+
+
+	@Component
+	static class L0ConfigEmpty {
+
+		@Component
+		static class L1ConfigEmpty {
+
+			@Component
+			protected static class L2ConfigEmpty {
+			}
+		}
+	}
+
+
 	@Configuration
 	static class S1Config extends L0Config {
 		@Override
@@ -139,4 +223,4 @@ public TestBean overrideBean() {
 		}
 	}
 
-}
+}