Introduced support for @lazy on injection points

This turned into a rather huge affair since it led to the introduction of a new AutowireCandidateResolver implementation in the spring-context module. That ACR impl is now being set through AnnotationConfigUtils; GenericApplicationContext and co do not set a default QualifierAnnotationAutowireCandidateResolver anymore (which has always been a smell anyway).  At the same time, dependency ordering has moved from AutowiredAnnotationBeanPostProcessor to DefaultListableBeanFactory itself through a "dependencyComparator" strategy, applying to constructor dependencies and lazy resolution proxies as well.

Issue: SPR-10353

Author: jhoeller

spring-beans/src/main/java/org/springframework/beans/factory/annotation/AutowiredAnnotationBeanPostProcessor.java

@@ -57,7 +57,6 @@
 import org.springframework.core.PriorityOrdered;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.core.annotation.AnnotationAttributes;
-import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
@@ -436,10 +435,7 @@ private void registerDependentBeans(String beanName, Set<String> autowiredBeanNa
 	private Object resolvedCachedArgument(String beanName, Object cachedArgument) {
 		if (cachedArgument instanceof DependencyDescriptor) {
 			DependencyDescriptor descriptor = (DependencyDescriptor) cachedArgument;
-			TypeConverter typeConverter = this.beanFactory.getTypeConverter();
-			Object value = this.beanFactory.resolveDependency(descriptor, beanName, null, typeConverter);
-			AnnotationAwareOrderComparator.sortIfNecessary(value);
-			return value;
+			return this.beanFactory.resolveDependency(descriptor, beanName, null, null);
 		}
 		else if (cachedArgument instanceof RuntimeBeanReference) {
 			return this.beanFactory.getBean(((RuntimeBeanReference) cachedArgument).getBeanName());
@@ -479,7 +475,6 @@ protected void inject(Object bean, String beanName, PropertyValues pvs) throws T
 					Set<String> autowiredBeanNames = new LinkedHashSet<String>(1);
 					TypeConverter typeConverter = beanFactory.getTypeConverter();
 					value = beanFactory.resolveDependency(descriptor, beanName, autowiredBeanNames, typeConverter);
-					AnnotationAwareOrderComparator.sortIfNecessary(value);
 					synchronized (this) {
 						if (!this.cached) {
 							if (value != null || this.required) {
@@ -557,7 +552,6 @@ protected void inject(Object bean, String beanName, PropertyValues pvs) throws T
 							arguments = null;
 							break;
 						}
-						AnnotationAwareOrderComparator.sortIfNecessary(arg);
 						arguments[i] = arg;
 					}
 					synchronized (this) {

spring-beans/src/main/java/org/springframework/beans/factory/annotation/QualifierAnnotationAutowireCandidateResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -131,6 +131,10 @@ public void setBeanFactory(BeanFactory beanFactory) {
 		this.beanFactory = beanFactory;
 	}
 
+	protected final BeanFactory getBeanFactory() {
+		return this.beanFactory;
+	}
+
 
 	/**
 	 * Determine whether the provided bean definition is an autowire candidate.
@@ -336,4 +340,14 @@ protected Object extractValue(Annotation valueAnnotation) {
 		return value;
 	}
 
+
+	/**
+	 * This implementation always returns {@code null},
+	 * leaving lazy resolution support up to subclasses.
+	 */
+	@Override
+	public Object getLazyResolutionProxyIfNecessary(DependencyDescriptor descriptor, String beanName) {
+		return null;
+	}
+
 }

spring-beans/src/main/java/org/springframework/beans/factory/support/AutowireCandidateResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -23,8 +23,8 @@
  * Strategy interface for determining whether a specific bean definition
  * qualifies as an autowire candidate for a specific dependency.
  *
- * @author Mark Fisher
  * @author Juergen Hoeller
+ * @author Mark Fisher
  * @since 2.5
  */
 public interface AutowireCandidateResolver {
@@ -47,4 +47,15 @@ public interface AutowireCandidateResolver {
 	 */
 	Object getSuggestedValue(DependencyDescriptor descriptor);
 
+	/**
+	 * Build a proxy for lazy resolution of the actual dependency target,
+	 * if demanded by the injection point.
+	 * @param descriptor the descriptor for the target method parameter or field
+	 * @param beanName the name of the bean that contains the injection point
+	 * @return the lazy resolution proxy for the actual dependency target,
+	 * or {@code null} if straight resolution is to be performed
+	 * @since 4.0
+	 */
+	Object getLazyResolutionProxyIfNecessary(DependencyDescriptor descriptor, String beanName);
+
 }

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -29,6 +29,8 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -125,6 +127,9 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 	/** Whether to allow eager class loading even for lazy-init beans */
 	private boolean allowEagerClassLoading = true;
 
+	/** Optional OrderComparator for dependency Lists and arrays */
+	private Comparator dependencyComparator;
+
 	/** Resolver to use for checking if a bean definition is an autowire candidate */
 	private AutowireCandidateResolver autowireCandidateResolver = new SimpleAutowireCandidateResolver();
 
@@ -205,6 +210,22 @@ public void setAllowEagerClassLoading(boolean allowEagerClassLoading) {
 		this.allowEagerClassLoading = allowEagerClassLoading;
 	}
 
+	/**
+	 * Set a {@link java.util.Comparator} for dependency Lists and arrays.
+	 * @see org.springframework.core.OrderComparator
+	 * @see org.springframework.core.annotation.AnnotationAwareOrderComparator
+	 */
+	public void setDependencyComparator(Comparator dependencyComparator) {
+		this.dependencyComparator = dependencyComparator;
+	}
+
+	/**
+	 * Return the dependency comparator for this BeanFactory (may be {@code null}.
+	 */
+	public Comparator getDependencyComparator() {
+		return this.dependencyComparator;
+	}
+
 	/**
 	 * Set a custom autowire candidate resolver for this BeanFactory to use
 	 * when deciding whether a bean definition should be considered as a
@@ -786,13 +807,18 @@ else if (descriptor.getDependencyType().equals(javaxInjectProviderClass)) {
 			return new DependencyProviderFactory().createDependencyProvider(descriptor, beanName);
 		}
 		else {
-			return doResolveDependency(descriptor, descriptor.getDependencyType(), beanName, autowiredBeanNames, typeConverter);
+			Object result = getAutowireCandidateResolver().getLazyResolutionProxyIfNecessary(descriptor, beanName);
+			if (result == null) {
+				result = doResolveDependency(descriptor, beanName, autowiredBeanNames, typeConverter);
+			}
+			return result;
 		}
 	}
 
-	protected Object doResolveDependency(DependencyDescriptor descriptor, Class<?> type, String beanName,
+	public Object doResolveDependency(DependencyDescriptor descriptor, String beanName,
 			Set<String> autowiredBeanNames, TypeConverter typeConverter) throws BeansException {
 
+		Class<?> type = descriptor.getDependencyType();
 		Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);
 		if (value != null) {
 			if (value instanceof String) {
@@ -819,7 +845,11 @@ protected Object doResolveDependency(DependencyDescriptor descriptor, Class<?> t
 				autowiredBeanNames.addAll(matchingBeans.keySet());
 			}
 			TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
-			return converter.convertIfNecessary(matchingBeans.values(), type);
+			Object result = converter.convertIfNecessary(matchingBeans.values(), type);
+			if (this.dependencyComparator != null && result instanceof Object[]) {
+				Arrays.sort((Object[]) result, this.dependencyComparator);
+			}
+			return result;
 		}
 		else if (Collection.class.isAssignableFrom(type) && type.isInterface()) {
 			Class<?> elementType = descriptor.getCollectionType();
@@ -840,7 +870,11 @@ else if (Collection.class.isAssignableFrom(type) && type.isInterface()) {
 				autowiredBeanNames.addAll(matchingBeans.keySet());
 			}
 			TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
-			return converter.convertIfNecessary(matchingBeans.values(), type);
+			Object result = converter.convertIfNecessary(matchingBeans.values(), type);
+			if (this.dependencyComparator != null && result instanceof List) {
+				Collections.sort((List) result, this.dependencyComparator);
+			}
+			return result;
 		}
 		else if (Map.class.isAssignableFrom(type) && type.isInterface()) {
 			Class<?> keyType = descriptor.getMapKeyType();
@@ -1091,7 +1125,7 @@ public DependencyObjectFactory(DependencyDescriptor descriptor, String beanName)
 
 		@Override
 		public Object getObject() throws BeansException {
-			return doResolveDependency(this.descriptor, this.descriptor.getDependencyType(), this.beanName, null, null);
+			return doResolveDependency(this.descriptor, this.beanName, null, null);
 		}
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/support/SimpleAutowireCandidateResolver.java

@@ -1,6 +1,5 @@
-
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -47,4 +46,9 @@ public Object getSuggestedValue(DependencyDescriptor descriptor) {
 		return null;
 	}
 
+	@Override
+	public Object getLazyResolutionProxyIfNecessary(DependencyDescriptor descriptor, String beanName) {
+		return null;
+	}
+
 }

spring-beans/src/test/java/org/springframework/beans/factory/annotation/AutowiredAnnotationBeanPostProcessorTests.java

@@ -37,6 +37,7 @@
 import org.springframework.beans.factory.support.GenericBeanDefinition;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.core.Ordered;
+import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.core.annotation.Order;
 import org.springframework.tests.sample.beans.ITestBean;
 import org.springframework.tests.sample.beans.IndexedTestBean;
@@ -46,16 +47,13 @@
 
 import static org.junit.Assert.*;
 
-
 /**
- * Unit tests for {@link AutowiredAnnotationBeanPostProcessor}.
- *
  * @author Juergen Hoeller
  * @author Mark Fisher
  * @author Sam Brannen
  * @author Chris Beams
  */
-public final class AutowiredAnnotationBeanPostProcessorTests {
+public class AutowiredAnnotationBeanPostProcessorTests {
 
 	@Test
 	public void testIncompleteBeanDefinition() {
@@ -348,6 +346,7 @@ public void testOptionalResourceInjectionWithNoDependencies() {
 	@Test
 	public void testOrderedResourceInjection() {
 		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
 		AutowiredAnnotationBeanPostProcessor bpp = new AutowiredAnnotationBeanPostProcessor();
 		bpp.setBeanFactory(bf);
 		bf.addBeanPostProcessor(bpp);
@@ -381,6 +380,7 @@ public void testOrderedResourceInjection() {
 	@Test
 	public void testAnnotationOrderedResourceInjection() {
 		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
 		AutowiredAnnotationBeanPostProcessor bpp = new AutowiredAnnotationBeanPostProcessor();
 		bpp.setBeanFactory(bf);
 		bf.addBeanPostProcessor(bpp);
@@ -412,6 +412,7 @@ public void testAnnotationOrderedResourceInjection() {
 	@Test
 	public void testOrderedCollectionResourceInjection() {
 		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
 		AutowiredAnnotationBeanPostProcessor bpp = new AutowiredAnnotationBeanPostProcessor();
 		bpp.setBeanFactory(bf);
 		bf.addBeanPostProcessor(bpp);
@@ -452,6 +453,7 @@ public void testOrderedCollectionResourceInjection() {
 	@Test
 	public void testAnnotationOrderedCollectionResourceInjection() {
 		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
 		AutowiredAnnotationBeanPostProcessor bpp = new AutowiredAnnotationBeanPostProcessor();
 		bpp.setBeanFactory(bf);
 		bf.addBeanPostProcessor(bpp);
@@ -566,6 +568,55 @@ public void testConstructorResourceInjectionWithMultipleCandidatesAsCollection()
 		bf.destroySingletons();
 	}
 
+	@Test
+	public void testConstructorResourceInjectionWithMultipleOrderedCandidates() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
+		AutowiredAnnotationBeanPostProcessor bpp = new AutowiredAnnotationBeanPostProcessor();
+		bpp.setBeanFactory(bf);
+		bf.addBeanPostProcessor(bpp);
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(ConstructorsResourceInjectionBean.class));
+		TestBean tb = new TestBean();
+		bf.registerSingleton("testBean", tb);
+		FixedOrder2NestedTestBean ntb1 = new FixedOrder2NestedTestBean();
+		bf.registerSingleton("nestedTestBean1", ntb1);
+		FixedOrder1NestedTestBean ntb2 = new FixedOrder1NestedTestBean();
+		bf.registerSingleton("nestedTestBean2", ntb2);
+
+		ConstructorsResourceInjectionBean bean = (ConstructorsResourceInjectionBean) bf.getBean("annotatedBean");
+		assertNull(bean.getTestBean3());
+		assertSame(tb, bean.getTestBean4());
+		assertEquals(2, bean.getNestedTestBeans().length);
+		assertSame(ntb2, bean.getNestedTestBeans()[0]);
+		assertSame(ntb1, bean.getNestedTestBeans()[1]);
+		bf.destroySingletons();
+	}
+
+	@Test
+	public void testConstructorResourceInjectionWithMultipleCandidatesAsOrderedCollection() {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		bf.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
+		AutowiredAnnotationBeanPostProcessor bpp = new AutowiredAnnotationBeanPostProcessor();
+		bpp.setBeanFactory(bf);
+		bf.addBeanPostProcessor(bpp);
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(
+				ConstructorsCollectionResourceInjectionBean.class));
+		TestBean tb = new TestBean();
+		bf.registerSingleton("testBean", tb);
+		FixedOrder2NestedTestBean ntb1 = new FixedOrder2NestedTestBean();
+		bf.registerSingleton("nestedTestBean1", ntb1);
+		FixedOrder1NestedTestBean ntb2 = new FixedOrder1NestedTestBean();
+		bf.registerSingleton("nestedTestBean2", ntb2);
+
+		ConstructorsCollectionResourceInjectionBean bean = (ConstructorsCollectionResourceInjectionBean) bf.getBean("annotatedBean");
+		assertNull(bean.getTestBean3());
+		assertSame(tb, bean.getTestBean4());
+		assertEquals(2, bean.getNestedTestBeans().size());
+		assertSame(ntb2, bean.getNestedTestBeans().get(0));
+		assertSame(ntb1, bean.getNestedTestBeans().get(1));
+		bf.destroySingletons();
+	}
+
 	@Test
 	public void testConstructorResourceInjectionWithMultipleCandidatesAndFallback() {
 		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
@@ -1102,7 +1153,6 @@ public static class ResourceInjectionBean {
 
 		private TestBean testBean2;
 
-
 		@Autowired
 		public void setTestBean2(TestBean testBean2) {
 			if (this.testBean2 != null) {

spring-beans/src/test/java/org/springframework/beans/factory/annotation/CustomAutowireConfigurerTests.java

@@ -16,10 +16,8 @@
 
 package org.springframework.beans.factory.annotation;
 
-import static org.junit.Assert.assertEquals;
-import static org.springframework.tests.TestResourceUtils.qualifiedResource;
-
 import org.junit.Test;
+
 import org.springframework.beans.factory.config.BeanDefinitionHolder;
 import org.springframework.beans.factory.config.DependencyDescriptor;
 import org.springframework.beans.factory.support.AutowireCandidateResolver;
@@ -28,6 +26,9 @@
 import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
 import org.springframework.core.io.Resource;
 
+import static org.junit.Assert.*;
+import static org.springframework.tests.TestResourceUtils.*;
+
 /**
  * Unit tests for {@link CustomAutowireConfigurer}.
  *
@@ -87,6 +88,11 @@ public boolean isAutowireCandidate(BeanDefinitionHolder bdHolder, DependencyDesc
 		public Object getSuggestedValue(DependencyDescriptor descriptor) {
 			return null;
 		}
+
+		@Override
+		public Object getLazyResolutionProxyIfNecessary(DependencyDescriptor descriptor, String beanName) {
+			return null;
+		}
 	}
 
 }