ComponentScan annotation allows for registering beans with lazy initialization

Issue: SPR-10459

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

 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -163,6 +163,14 @@ public class ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateCo
 				(beanDefinitionDefaults != null ? beanDefinitionDefaults : new BeanDefinitionDefaults());
 	}
 
+	/**
+	 * Return the defaults to use for detected beans (never {@code null}).
+	 * @since 4.1
+	 */
+	public BeanDefinitionDefaults getBeanDefinitionDefaults() {
+		return this.beanDefinitionDefaults;
+	}
+
 	/**
 	 * Set the name-matching patterns for determining autowire candidates.
 	 * @param autowireCandidatePatterns the patterns to match against

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

 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -132,6 +132,13 @@ public @interface ComponentScan {
 	 */
 	Filter[] excludeFilters() default {};
 
+	/**
+	 * Specify whether scanned beans should be registered for lazy initialization.
+	 * <p>Default is {@code false}; switch this to {@code true} when desired.
+	 * @since 4.1
+	 */
+	boolean lazyInit() default false;
+
 
 	/**
 	 * Declares the type filter to be used as an {@linkplain ComponentScan#includeFilters()

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

 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -106,6 +106,11 @@ class ComponentScanAnnotationParser {
 			}
 		}
 
+		boolean lazyInit = componentScan.getBoolean("lazyInit");
+		if (lazyInit) {
+			scanner.getBeanDefinitionDefaults().setLazyInit(true);
+		}
+
 		List<String> basePackages = new ArrayList<String>();
 		for (String pkg : componentScan.getStringArray("value")) {
 			if (StringUtils.hasText(pkg)) {

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

@@ -23,7 +23,17 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 import java.util.HashSet;
 
+import example.scannable.CustomComponent;
+import example.scannable.CustomStereotype;
+import example.scannable.DefaultNamedComponent;
+import example.scannable.FooService;
+import example.scannable.MessageBean;
+import example.scannable.ScopedProxyTestBean;
+import example.scannable_implicitbasepackage.ComponentScanAnnotatedConfigWithImplicitBasePackage;
+import example.scannable_scoped.CustomScopeAnnotationBean;
+import example.scannable_scoped.MyScope;
 import org.junit.Test;
+
 import org.springframework.aop.support.AopUtils;
 import org.springframework.beans.factory.annotation.CustomAutowireConfigurer;
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -36,16 +46,6 @@ import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.tests.context.SimpleMapScope;
 import org.springframework.util.SerializationTestUtils;
 
-import example.scannable.CustomComponent;
-import example.scannable.CustomStereotype;
-import example.scannable.DefaultNamedComponent;
-import example.scannable.FooService;
-import example.scannable.MessageBean;
-import example.scannable.ScopedProxyTestBean;
-import example.scannable_implicitbasepackage.ComponentScanAnnotatedConfigWithImplicitBasePackage;
-import example.scannable_scoped.CustomScopeAnnotationBean;
-import example.scannable_scoped.MyScope;
-
 import static org.hamcrest.CoreMatchers.*;
 import static org.junit.Assert.*;
 import static org.springframework.beans.factory.support.BeanDefinitionBuilder.*;
@@ -116,10 +116,10 @@ public class ComponentScanAnnotationIntegrationTests {
 		ctx.getBean(ComposedAnnotationConfig.class);
 		ctx.getBean(SimpleComponent.class);
 		assertThat("config class bean not found",
-			ctx.containsBeanDefinition("componentScanAnnotationIntegrationTests.ComposedAnnotationConfig"), is(true));
-		assertThat("@ComponentScan annotated @Configuration class registered directly against "
-				+ "AnnotationConfigApplicationContext did not trigger component scanning as expected",
-			ctx.containsBean("simpleComponent"), is(true));
+				ctx.containsBeanDefinition("componentScanAnnotationIntegrationTests.ComposedAnnotationConfig"), is(true));
+		assertThat("@ComponentScan annotated @Configuration class registered directly against " +
+						"AnnotationConfigApplicationContext did not trigger component scanning as expected",
+				ctx.containsBean("simpleComponent"), is(true));
 	}
 
 	@Test
@@ -159,7 +159,8 @@ public class ComponentScanAnnotationIntegrationTests {
 	@Test
 	public void withCustomTypeFilter() {
 		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(ComponentScanWithCustomTypeFilter.class);
-		KustomAnnotationAutowiredBean testBean = ctx.getBean(KustomAnnotationAutowiredBean.class);
+		assertFalse(ctx.getDefaultListableBeanFactory().containsSingleton("kustomBean"));
+		KustomAnnotationAutowiredBean testBean = ctx.getBean("kustomBean", KustomAnnotationAutowiredBean.class);
 		assertThat(testBean.getDependency(), notNullValue());
 	}
 
@@ -294,7 +295,8 @@ class MyScopeMetadataResolver extends AnnotationScopeMetadataResolver {
 		useDefaultFilters=false,
 		includeFilters=@Filter(type=FilterType.CUSTOM, value=ComponentScanParserTests.CustomTypeFilter.class),
 		// exclude this class from scanning since it's in the scanned package
-		excludeFilters=@Filter(type=FilterType.ASSIGNABLE_TYPE, value=ComponentScanWithCustomTypeFilter.class))
+		excludeFilters=@Filter(type=FilterType.ASSIGNABLE_TYPE, value=ComponentScanWithCustomTypeFilter.class),
+		lazyInit = true)
 class ComponentScanWithCustomTypeFilter {
 	@Bean
 	@SuppressWarnings({ "rawtypes", "serial", "unchecked" })

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

 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2014 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package org.springframework.context.annotation;
 
 import org.junit.Test;
+
 import org.springframework.beans.factory.support.DefaultBeanNameGenerator;
 import org.springframework.context.annotation.ComponentScan.Filter;
 import org.springframework.core.type.filter.TypeFilter;
@@ -29,6 +30,7 @@ import org.springframework.core.type.filter.TypeFilter;
  * @see ComponentScanAnnotationIntegrationTests
  */
 public class ComponentScanAnnotationTests {
+
 	@Test
 	public void noop() {
 		// no-op; the @ComponentScan-annotated MyConfig class below simply excercises
@@ -36,7 +38,9 @@ public class ComponentScanAnnotationTests {
 	}
 }
 
-@interface MyAnnotation { }
+
+@interface MyAnnotation {
+}
 
 @Configuration
 @ComponentScan(
@@ -44,18 +48,19 @@ public class ComponentScanAnnotationTests {
 	nameGenerator = DefaultBeanNameGenerator.class,
 	scopedProxy = ScopedProxyMode.NO,
 	scopeResolver = AnnotationScopeMetadataResolver.class,
-	useDefaultFilters = false,
 	resourcePattern = "**/*custom.class",
+	useDefaultFilters = false,
 	includeFilters = {
 		@Filter(type = FilterType.ANNOTATION, value = MyAnnotation.class)
 	},
 	excludeFilters = {
 		@Filter(type = FilterType.CUSTOM, value = TypeFilter.class)
-	}
+	},
+	lazyInit = true
 )
 class MyConfig {
-
 }
 
 @ComponentScan(basePackageClasses=example.scannable.NamedComponent.class)
-class SimpleConfig { }
\ No newline at end of file
+class SimpleConfig {
+}

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

@@ -21,7 +21,10 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+import example.profilescan.ProfileAnnotatedComponent;
+import example.scannable.AutowiredQualifierFooService;
 import org.junit.Test;
+
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
@@ -29,9 +32,7 @@ import org.springframework.context.support.GenericXmlApplicationContext;
 import org.springframework.core.type.classreading.MetadataReader;
 import org.springframework.core.type.classreading.MetadataReaderFactory;
 import org.springframework.core.type.filter.TypeFilter;
-
-import example.profilescan.ProfileAnnotatedComponent;
-import example.scannable.AutowiredQualifierFooService;
+import org.springframework.stereotype.Component;
 
 import static org.hamcrest.CoreMatchers.*;
 import static org.junit.Assert.*;
@@ -134,13 +135,13 @@ public class ComponentScanParserTests {
 	 * Intentionally spelling "custom" with a "k" since there are numerous
 	 * classes in this package named *Custom*.
 	 */
+	@Component("kustomBean")
 	public static class KustomAnnotationAutowiredBean {
 
 		@Autowired
 		@CustomAnnotation
 		private KustomAnnotationDependencyBean dependency;
 
-
 		public KustomAnnotationDependencyBean getDependency() {
 			return this.dependency;
 		}