Revise FactoryBean locking behavior for strict/lenient consistency

After the bootstrap phase (and with spring.locking.strict=true during the bootstrap phase), getSingletonFactoryBeanForTypeCheck always locks. In a background bootstrap thread, it never locks. Otherwise, it tries locking and explicitly resolves the bean class for subsequent type-based resolution (even for a component-scanned class) when it fails to acquire the lock. Furthermore, getObjectFromFactoryBean follows the same locking algorithm for post-processing.

Closes gh-34902

Author: jhoeller

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

@@ -997,9 +997,17 @@ protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd,
 	 */
 	@Nullable
 	private FactoryBean<?> getSingletonFactoryBeanForTypeCheck(String beanName, RootBeanDefinition mbd) {
-		boolean locked = this.singletonLock.tryLock();
-		if (!locked) {
-			return null;
+		Boolean lockFlag = isCurrentThreadAllowedToHoldSingletonLock();
+		if (lockFlag == null) {
+			this.singletonLock.lock();
+		}
+		else {
+			boolean locked = (lockFlag && this.singletonLock.tryLock());
+			if (!locked) {
+				// Avoid shortcut FactoryBean instance but allow for subsequent type-based resolution.
+				resolveBeanClass(mbd, beanName);
+				return null;
+			}
 		}
 
 		try {

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

@@ -271,13 +271,15 @@ public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
 						// Fallback as of 6.2: process given singleton bean outside of singleton lock.
 						// Thread-safe exposure is still guaranteed, there is just a risk of collisions
 						// when triggering creation of other beans as dependencies of the current bean.
-						if (logger.isInfoEnabled()) {
-							logger.info("Obtaining singleton bean '" + beanName + "' in thread \"" +
-									Thread.currentThread().getName() + "\" while other thread holds " +
-									"singleton lock for other beans " + this.singletonsCurrentlyInCreation);
-						}
 						this.lenientCreationLock.lock();
 						try {
+							if (logger.isInfoEnabled()) {
+								Set<String> lockedBeans = new HashSet<>(this.singletonsCurrentlyInCreation);
+								lockedBeans.removeAll(this.singletonsInLenientCreation);
+								logger.info("Obtaining singleton bean '" + beanName + "' in thread \"" +
+										currentThread.getName() + "\" while other thread holds singleton " +
+										"lock for other beans " + lockedBeans);
+							}
 							this.singletonsInLenientCreation.add(beanName);
 						}
 						finally {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -118,7 +118,15 @@ protected Object getCachedObjectForFactoryBean(String beanName) {
 	 */
 	protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {
 		if (factory.isSingleton() && containsSingleton(beanName)) {
-			this.singletonLock.lock();
+			Boolean lockFlag = isCurrentThreadAllowedToHoldSingletonLock();
+			boolean locked;
+			if (lockFlag == null) {
+				this.singletonLock.lock();
+				locked = true;
+			}
+			else {
+				locked = (lockFlag && this.singletonLock.tryLock());
+			}
 			try {
 				Object object = this.factoryBeanObjectCache.get(beanName);
 				if (object == null) {
@@ -131,11 +139,13 @@ protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanNam
 					}
 					else {
 						if (shouldPostProcess) {
-							if (isSingletonCurrentlyInCreation(beanName)) {
-								// Temporarily return non-post-processed object, not storing it yet
-								return object;
+							if (locked) {
+								if (isSingletonCurrentlyInCreation(beanName)) {
+									// Temporarily return non-post-processed object, not storing it yet
+									return object;
+								}
+								beforeSingletonCreation(beanName);
 							}
-							beforeSingletonCreation(beanName);
 							try {
 								object = postProcessObjectFromFactoryBean(object, beanName);
 							}
@@ -144,7 +154,9 @@ protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanNam
 										"Post-processing of FactoryBean's singleton object failed", ex);
 							}
 							finally {
-								afterSingletonCreation(beanName);
+								if (locked) {
+									afterSingletonCreation(beanName);
+								}
 							}
 						}
 						if (containsSingleton(beanName)) {
@@ -155,7 +167,9 @@ protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanNam
 				return object;
 			}
 			finally {
-				this.singletonLock.unlock();
+				if (locked) {
+					this.singletonLock.unlock();
+				}
 			}
 		}
 		else {

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

@@ -24,6 +24,7 @@
 
 import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.BeanCurrentlyInCreationException;
+import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.UnsatisfiedDependencyException;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
@@ -243,14 +244,24 @@ public TestBean testBean3(TestBean testBean4) {
 		}
 
 		@Bean
-		public TestBean testBean4() {
+		public FactoryBean<TestBean> testBean4() {
 			try {
 				Thread.sleep(2000);
 			}
 			catch (InterruptedException ex) {
 				Thread.currentThread().interrupt();
 			}
-			return new TestBean();
+			TestBean testBean = new TestBean();
+			return new FactoryBean<>() {
+				@Override
+				public TestBean getObject() {
+					return testBean;
+				}
+				@Override
+				public Class<?> getObjectType() {
+					return testBean.getClass();
+				}
+			};
 		}
 	}