Avoid unnecessary CGLIB processing on configuration classes

Closes gh-34486

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClass.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.
@@ -203,6 +203,15 @@ final class ConfigurationClass {
 		return this.beanMethods;
 	}
 
+	boolean hasNonStaticBeanMethods() {
+		for (BeanMethod beanMethod : this.beanMethods) {
+			if (!beanMethod.getMetadata().isStatic()) {
+				return true;
+			}
+		}
+		return false;
+	}
+
 	void addImportedResource(String importedResource, Class<? extends BeanDefinitionReader> readerClass) {
 		this.importedResources.put(importedResource, readerClass);
 	}
@@ -223,8 +232,9 @@ final class ConfigurationClass {
 	void validate(ProblemReporter problemReporter) {
 		Map<String, Object> attributes = this.metadata.getAnnotationAttributes(Configuration.class.getName());
 
-		// A configuration class may not be final (CGLIB limitation) unless it declares proxyBeanMethods=false
+		// A configuration class may not be final (CGLIB limitation) unless it does not have to proxy bean methods
-		if (attributes != null && (Boolean) attributes.get("proxyBeanMethods") && this.metadata.isFinal()) {
+		if (attributes != null && (Boolean) attributes.get("proxyBeanMethods") && hasNonStaticBeanMethods() &&
+				this.metadata.isFinal()) {
 			problemReporter.error(new FinalConfigurationProblem());
 		}
 

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassParser.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.
@@ -167,14 +167,22 @@ class ConfigurationClassParser {
 		for (BeanDefinitionHolder holder : configCandidates) {
 			BeanDefinition bd = holder.getBeanDefinition();
 			try {
+				ConfigurationClass configClass;
 				if (bd instanceof AnnotatedBeanDefinition annotatedBeanDef) {
-					parse(annotatedBeanDef, holder.getBeanName());
+					configClass = parse(annotatedBeanDef, holder.getBeanName());
 				}
 				else if (bd instanceof AbstractBeanDefinition abstractBeanDef && abstractBeanDef.hasBeanClass()) {
-					parse(abstractBeanDef.getBeanClass(), holder.getBeanName());
+					configClass = parse(abstractBeanDef.getBeanClass(), holder.getBeanName());
 				}
 				else {
-					parse(bd.getBeanClassName(), holder.getBeanName());
+					configClass = parse(bd.getBeanClassName(), holder.getBeanName());
+				}
+
+				// Downgrade to lite (no enhancement) in case of no instance-level @Bean methods.
+				if (!configClass.hasNonStaticBeanMethods() && ConfigurationClassUtils.CONFIGURATION_CLASS_FULL.equals(
+						bd.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE))) {
+					bd.setAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE,
+							ConfigurationClassUtils.CONFIGURATION_CLASS_LITE);
 				}
 			}
 			catch (BeanDefinitionStoreException ex) {
@@ -189,20 +197,25 @@ class ConfigurationClassParser {
 		this.deferredImportSelectorHandler.process();
 	}
 
-	private void parse(AnnotatedBeanDefinition beanDef, String beanName) {
+	private ConfigurationClass parse(AnnotatedBeanDefinition beanDef, String beanName) {
-		processConfigurationClass(
+		ConfigurationClass configClass = new ConfigurationClass(
-				new ConfigurationClass(beanDef.getMetadata(), beanName, (beanDef instanceof ScannedGenericBeanDefinition)),
+				beanDef.getMetadata(), beanName, (beanDef instanceof ScannedGenericBeanDefinition));
-				DEFAULT_EXCLUSION_FILTER);
+		processConfigurationClass(configClass, DEFAULT_EXCLUSION_FILTER);
+		return configClass;
 	}
 
-	private void parse(Class<?> clazz, String beanName) {
+	private ConfigurationClass parse(Class<?> clazz, String beanName) {
-		processConfigurationClass(new ConfigurationClass(clazz, beanName), DEFAULT_EXCLUSION_FILTER);
+		ConfigurationClass configClass = new ConfigurationClass(clazz, beanName);
+		processConfigurationClass(configClass, DEFAULT_EXCLUSION_FILTER);
+		return configClass;
 	}
 
-	final void parse(@Nullable String className, String beanName) throws IOException {
+	final ConfigurationClass parse(@Nullable String className, String beanName) throws IOException {
 		Assert.notNull(className, "No bean class name for configuration class bean definition");
 		MetadataReader reader = this.metadataReaderFactory.getMetadataReader(className);
-		processConfigurationClass(new ConfigurationClass(reader, beanName), DEFAULT_EXCLUSION_FILTER);
+		ConfigurationClass configClass = new ConfigurationClass(reader, beanName);
+		processConfigurationClass(configClass, DEFAULT_EXCLUSION_FILTER);
+		return configClass;
 	}
 
 	/**

spring-context/src/test/java/org/springframework/context/annotation/ConfigurationClassPostProcessorTests.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.
@@ -67,6 +67,7 @@ import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.core.task.SyncTaskExecutor;
 import org.springframework.stereotype.Component;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
@@ -104,6 +105,7 @@ class ConfigurationClassPostProcessorTests {
 		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
 		pp.postProcessBeanFactory(beanFactory);
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).hasBeanClass()).isTrue();
+		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).getBeanClass().getName()).contains(ClassUtils.CGLIB_CLASS_SEPARATOR);
 		Foo foo = beanFactory.getBean("foo", Foo.class);
 		Bar bar = beanFactory.getBean("bar", Bar.class);
 		assertThat(bar.foo).isSameAs(foo);
@@ -118,6 +120,7 @@ class ConfigurationClassPostProcessorTests {
 		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
 		pp.postProcessBeanFactory(beanFactory);
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).hasBeanClass()).isTrue();
+		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).getBeanClass().getName()).contains(ClassUtils.CGLIB_CLASS_SEPARATOR);
 		Foo foo = beanFactory.getBean("foo", Foo.class);
 		Bar bar = beanFactory.getBean("bar", Bar.class);
 		assertThat(bar.foo).isSameAs(foo);
@@ -132,6 +135,7 @@ class ConfigurationClassPostProcessorTests {
 		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
 		pp.postProcessBeanFactory(beanFactory);
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).hasBeanClass()).isTrue();
+		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).getBeanClass().getName()).doesNotContain(ClassUtils.CGLIB_CLASS_SEPARATOR);
 		Foo foo = beanFactory.getBean("foo", Foo.class);
 		Bar bar = beanFactory.getBean("bar", Bar.class);
 		assertThat(bar.foo).isNotSameAs(foo);
@@ -143,6 +147,7 @@ class ConfigurationClassPostProcessorTests {
 		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
 		pp.postProcessBeanFactory(beanFactory);
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).hasBeanClass()).isTrue();
+		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).getBeanClass().getName()).doesNotContain(ClassUtils.CGLIB_CLASS_SEPARATOR);
 		Foo foo = beanFactory.getBean("foo", Foo.class);
 		Bar bar = beanFactory.getBean("bar", Bar.class);
 		assertThat(bar.foo).isNotSameAs(foo);
@@ -154,6 +159,7 @@ class ConfigurationClassPostProcessorTests {
 		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
 		pp.postProcessBeanFactory(beanFactory);
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).hasBeanClass()).isTrue();
+		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).getBeanClass().getName()).doesNotContain(ClassUtils.CGLIB_CLASS_SEPARATOR);
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("foo")).hasBeanClass()).isTrue();
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("bar")).hasBeanClass()).isTrue();
 		Foo foo = beanFactory.getBean("foo", Foo.class);
@@ -167,6 +173,7 @@ class ConfigurationClassPostProcessorTests {
 		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
 		pp.postProcessBeanFactory(beanFactory);
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).hasBeanClass()).isTrue();
+		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).getBeanClass().getName()).doesNotContain(ClassUtils.CGLIB_CLASS_SEPARATOR);
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("foo")).hasBeanClass()).isTrue();
 		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("bar")).hasBeanClass()).isTrue();
 		Foo foo = beanFactory.getBean("foo", Foo.class);
@@ -174,6 +181,15 @@ class ConfigurationClassPostProcessorTests {
 		assertThat(bar.foo).isNotSameAs(foo);
 	}
 
+	@Test
+	void enhancementIsNotPresentWithEmptyConfig() {
+		beanFactory.registerBeanDefinition("config", new RootBeanDefinition(EmptyConfig.class));
+		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
+		pp.postProcessBeanFactory(beanFactory);
+		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).hasBeanClass()).isTrue();
+		assertThat(((RootBeanDefinition) beanFactory.getBeanDefinition("config")).getBeanClass().getName()).doesNotContain(ClassUtils.CGLIB_CLASS_SEPARATOR);
+	}
+
 	@Test
 	void configurationIntrospectionOfInnerClassesWorksWithDotNameSyntax() {
 		beanFactory.registerBeanDefinition("config", new RootBeanDefinition(getClass().getName() + ".SingletonBeanConfig"));
@@ -1166,7 +1182,7 @@ class ConfigurationClassPostProcessorTests {
 	}
 
 	@Configuration
-	static class StaticSingletonBeanConfig {
+	static final class StaticSingletonBeanConfig {
 
 		@Bean
 		public static Foo foo() {
@@ -1179,6 +1195,10 @@ class ConfigurationClassPostProcessorTests {
 		}
 	}
 
+	@Configuration
+	static final class EmptyConfig {
+	}
+
 	@Configuration
 	@Order(2)
 	static class OverridingSingletonBeanConfig {

spring-context/src/test/java/org/springframework/context/annotation/InvalidConfigurationClassDefinitionTests.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.
@@ -37,16 +37,18 @@ class InvalidConfigurationClassDefinitionTests {
 	@Test
 	void configurationClassesMayNotBeFinal() {
 		@Configuration
-		final class Config { }
+		final class Config {
+			@Bean String dummy() { return "dummy"; }
+		}
 
 		BeanDefinition configBeanDef = rootBeanDefinition(Config.class).getBeanDefinition();
 		DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
 		beanFactory.registerBeanDefinition("config", configBeanDef);
 
 		ConfigurationClassPostProcessor pp = new ConfigurationClassPostProcessor();
-		assertThatExceptionOfType(BeanDefinitionParsingException.class).isThrownBy(() ->
+		assertThatExceptionOfType(BeanDefinitionParsingException.class)
-				pp.postProcessBeanFactory(beanFactory))
+				.isThrownBy(() -> pp.postProcessBeanFactory(beanFactory))
-			.withMessageContaining("Remove the final modifier");
+				.withMessageContaining("Remove the final modifier");
 	}
 
 }

spring-context/src/testFixtures/java/org/springframework/context/testfixture/context/annotation/ValueCglibConfiguration.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.
@@ -17,6 +17,7 @@
 package org.springframework.context.testfixture.context.annotation;
 
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
 @Configuration
@@ -31,4 +32,10 @@ public class ValueCglibConfiguration {
 	public String getName() {
 		return this.name;
 	}
+
+	@Bean
+	public String dummy() {
+		return "dummy";
+	}
+
 }