Add BeanFactoryInitializer callback before preInstantiateSingletons

Closes gh-32836

Author: jhoeller

spring-beans/src/main/java/org/springframework/beans/factory/BeanFactoryInitializer.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2002-2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.beans.factory;
+
+/**
+ * Callback interface for initializing a Spring {@link ListableBeanFactory}
+ * prior to entering the singleton pre-instantiation phase. Can be used to
+ * trigger early initialization of specific beans before regular singletons.
+ *
+ * <p>Can be programmatically applied to a {@code ListableBeanFactory} instance.
+ * In an {@code ApplicationContext}, beans of type {@code BeanFactoryInitializer}
+ * will be autodetected and automatically applied to the underlying bean factory.
+ *
+ * @author Juergen Hoeller
+ * @since 6.2
+ * @param <F> the bean factory type
+ * @see org.springframework.beans.factory.config.ConfigurableListableBeanFactory#preInstantiateSingletons()
+ */
+public interface BeanFactoryInitializer<F extends ListableBeanFactory> {
+
+	/**
+	 * Initialize the given bean factory.
+	 * @param beanFactory the bean factory to bootstrap
+	 */
+	void initialize(F beanFactory);
+
+}

spring-context/src/main/java/org/springframework/context/ApplicationContextInitializer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -44,7 +44,7 @@ public interface ApplicationContextInitializer<C extends ConfigurableApplication
 
 	/**
 	 * Initialize the given application context.
-	 * @param applicationContext the application to configure
+	 * @param applicationContext the application context to bootstrap
 	 */
 	void initialize(C applicationContext);
 

spring-context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -37,6 +37,7 @@
 import org.springframework.beans.BeansException;
 import org.springframework.beans.CachedIntrospectionResults;
 import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanFactoryInitializer;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
@@ -932,6 +933,7 @@ protected void registerListeners() {
 	 * Finish the initialization of this context's bean factory,
 	 * initializing all remaining singleton beans.
 	 */
+	@SuppressWarnings("unchecked")
 	protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
 		// Initialize bootstrap executor for this context.
 		if (beanFactory.containsBean(BOOTSTRAP_EXECUTOR_BEAN_NAME) &&
@@ -954,6 +956,12 @@ protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory b
 			beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
 		}
 
+		// Call BeanFactoryInitializer beans early to allow for initializing specific other beans early.
+		String[] initializerNames = beanFactory.getBeanNamesForType(BeanFactoryInitializer.class, false, false);
+		for (String initializerName : initializerNames) {
+			beanFactory.getBean(initializerName, BeanFactoryInitializer.class).initialize(beanFactory);
+		}
+
 		// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
 		String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
 		for (String weaverAwareName : weaverAwareNames) {

spring-test/src/main/java/org/springframework/test/context/support/DynamicPropertySourceBeanInitializer.java

@@ -19,55 +19,30 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
-import org.springframework.beans.factory.BeanFactory;
-import org.springframework.beans.factory.BeanFactoryAware;
-import org.springframework.beans.factory.InitializingBean;
+import org.springframework.beans.factory.BeanFactoryInitializer;
 import org.springframework.beans.factory.ListableBeanFactory;
-import org.springframework.context.weaving.LoadTimeWeaverAware;
-import org.springframework.instrument.classloading.LoadTimeWeaver;
-import org.springframework.lang.Nullable;
 import org.springframework.test.context.DynamicPropertySource;
 
 /**
  * Internal component which eagerly initializes beans created by {@code @Bean}
  * factory methods annotated with {@link DynamicPropertySource @DynamicPropertySource}.
  *
- * <p>This class implements {@link LoadTimeWeaverAware} since doing so is
- * currently the only way to have a component eagerly initialized before the
- * {@code ConfigurableListableBeanFactory.preInstantiateSingletons()} phase.
- *
  * @author Sam Brannen
  * @since 6.2
  */
-class DynamicPropertySourceBeanInitializer implements BeanFactoryAware, InitializingBean, LoadTimeWeaverAware {
+class DynamicPropertySourceBeanInitializer implements BeanFactoryInitializer<ListableBeanFactory> {
 
 	private static final Log logger = LogFactory.getLog(DynamicPropertySourceBeanInitializer.class);
 
-	@Nullable
-	private BeanFactory beanFactory;
-
-
-	@Override
-	public void setBeanFactory(BeanFactory beanFactory) {
-		this.beanFactory = beanFactory;
-	}
 
 	@Override
-	public void afterPropertiesSet() {
-		if (!(this.beanFactory instanceof ListableBeanFactory lbf)) {
-			throw new IllegalStateException("BeanFactory must be set and must be a ListableBeanFactory");
-		}
-		for (String name : lbf.getBeanNamesForAnnotation(DynamicPropertySource.class)) {
+	public void initialize(ListableBeanFactory beanFactory) {
+		for (String name : beanFactory.getBeanNamesForAnnotation(DynamicPropertySource.class)) {
 			if (logger.isDebugEnabled()) {
 				logger.debug("Eagerly initializing @DynamicPropertySource bean '%s'".formatted(name));
 			}
-			this.beanFactory.getBean(name);
+			beanFactory.getBean(name);
 		}
 	}
 
-	@Override
-	public void setLoadTimeWeaver(LoadTimeWeaver loadTimeWeaver) {
-		// no-op
-	}
-
 }