Clear caches which are not needed after singleton instantiation

Closes gh-28293

Author: jhoeller

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

@@ -159,6 +159,9 @@
 public class AutowiredAnnotationBeanPostProcessor implements SmartInstantiationAwareBeanPostProcessor,
 		MergedBeanDefinitionPostProcessor, BeanRegistrationAotProcessor, PriorityOrdered, BeanFactoryAware {
 
+	private static final Constructor<?>[] EMPTY_CONSTRUCTOR_ARRAY = new Constructor<?>[0];
+
+
 	protected final Log logger = LogFactory.getLog(getClass());
 
 	private final Set<Class<? extends Annotation>> autowiredAnnotationTypes = new LinkedHashSet<>(4);
@@ -286,7 +289,25 @@ public void setBeanFactory(BeanFactory beanFactory) {
 
 	@Override
 	public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
+		// Register externally managed config members on bean definition.
 		findInjectionMetadata(beanName, beanType, beanDefinition);
+
+		// Use opportunity to clear caches which are not needed after singleton instantiation.
+		// The injectionMetadataCache itself is left intact since it cannot be reliably
+		// reconstructed in terms of externally managed config members otherwise.
+		if (beanDefinition.isSingleton()) {
+			this.candidateConstructorsCache.remove(beanType);
+			// With actual lookup overrides, keep it intact along with bean definition.
+			if (!beanDefinition.hasMethodOverrides()) {
+				this.lookupMethodsChecked.remove(beanName);
+			}
+		}
+	}
+
+	@Override
+	public void resetBeanDefinition(String beanName) {
+		this.lookupMethodsChecked.remove(beanName);
+		this.injectionMetadataCache.remove(beanName);
 	}
 
 	@Override
@@ -324,12 +345,6 @@ private InjectionMetadata findInjectionMetadata(String beanName, Class<?> beanTy
 		return metadata;
 	}
 
-	@Override
-	public void resetBeanDefinition(String beanName) {
-		this.lookupMethodsChecked.remove(beanName);
-		this.injectionMetadataCache.remove(beanName);
-	}
-
 	@Override
 	public Class<?> determineBeanType(Class<?> beanClass, String beanName) throws BeanCreationException {
 		checkLookupMethods(beanClass, beanName);
@@ -429,7 +444,7 @@ else if (candidates.size() == 1 && logger.isInfoEnabled()) {
 										"default constructor to fall back to: " + candidates.get(0));
 							}
 						}
-						candidateConstructors = candidates.toArray(new Constructor<?>[0]);
+						candidateConstructors = candidates.toArray(EMPTY_CONSTRUCTOR_ARRAY);
 					}
 					else if (rawCandidates.length == 1 && rawCandidates[0].getParameterCount() > 0) {
 						candidateConstructors = new Constructor<?>[] {rawCandidates[0]};
@@ -442,7 +457,7 @@ else if (nonSyntheticConstructors == 1 && primaryConstructor != null) {
 						candidateConstructors = new Constructor<?>[] {primaryConstructor};
 					}
 					else {
-						candidateConstructors = new Constructor<?>[0];
+						candidateConstructors = EMPTY_CONSTRUCTOR_ARRAY;
 					}
 					this.candidateConstructorsCache.put(beanClass, candidateConstructors);
 				}