Do not attempt to load pre-enhanced class for reloadable classes

Closes gh-33024

Author: jhoeller

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassEnhancer.java

@@ -49,6 +49,7 @@
 import org.springframework.cglib.proxy.NoOp;
 import org.springframework.cglib.transform.ClassEmitterTransformer;
 import org.springframework.cglib.transform.TransformingClassGenerator;
+import org.springframework.core.SmartClassLoader;
 import org.springframework.lang.Nullable;
 import org.springframework.objenesis.ObjenesisException;
 import org.springframework.objenesis.SpringObjenesis;
@@ -132,13 +133,21 @@ private Enhancer newEnhancer(Class<?> configSuperClass, @Nullable ClassLoader cl
 		enhancer.setInterfaces(new Class<?>[] {EnhancedConfiguration.class});
 		enhancer.setUseFactory(false);
 		enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
-		enhancer.setAttemptLoad(true);
+		enhancer.setAttemptLoad(!isClassReloadable(configSuperClass, classLoader));
 		enhancer.setStrategy(new BeanFactoryAwareGeneratorStrategy(classLoader));
 		enhancer.setCallbackFilter(CALLBACK_FILTER);
 		enhancer.setCallbackTypes(CALLBACK_FILTER.getCallbackTypes());
 		return enhancer;
 	}
 
+	/**
+	 * Checks whether the given configuration class is reloadable.
+	 */
+	private boolean isClassReloadable(Class<?> configSuperClass, @Nullable ClassLoader classLoader) {
+		return (classLoader instanceof SmartClassLoader smartClassLoader &&
+				smartClassLoader.isClassReloadable(configSuperClass));
+	}
+
 	/**
 	 * Uses enhancer to generate a subclass of superclass,
 	 * ensuring that callbacks are registered for the new subclass.

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

@@ -0,0 +1,87 @@
+/*
+ * 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.context.annotation;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.security.SecureClassLoader;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.core.SmartClassLoader;
+import org.springframework.util.StreamUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Phillip Webb
+ * @author Juergen Hoeller
+ */
+class ConfigurationClassEnhancerTests {
+
+	@Test
+	void enhanceReloadedClass() throws Exception {
+		ConfigurationClassEnhancer configurationClassEnhancer = new ConfigurationClassEnhancer();
+		ClassLoader parentClassLoader = getClass().getClassLoader();
+		CustomClassLoader classLoader = new CustomClassLoader(parentClassLoader);
+		Class<?> myClass = parentClassLoader.loadClass(MyConfig.class.getName());
+		configurationClassEnhancer.enhance(myClass, parentClassLoader);
+		Class<?> myReloadedClass = classLoader.loadClass(MyConfig.class.getName());
+		Class<?> enhancedReloadedClass = configurationClassEnhancer.enhance(myReloadedClass, classLoader);
+		assertThat(enhancedReloadedClass.getClassLoader()).isEqualTo(classLoader);
+	}
+
+
+	@Configuration
+	static class MyConfig {
+
+		@Bean
+		public String myBean() {
+			return "bean";
+		}
+	}
+
+
+	static class CustomClassLoader extends SecureClassLoader implements SmartClassLoader {
+
+		CustomClassLoader(ClassLoader parent) {
+			super(parent);
+		}
+
+		protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
+			if (name.contains("MyConfig")) {
+				String path = name.replace('.', '/').concat(".class");
+				try (InputStream in = super.getResourceAsStream(path)) {
+					byte[] bytes = StreamUtils.copyToByteArray(in);
+					if (bytes.length > 0) {
+						return defineClass(name, bytes, 0, bytes.length);
+					}
+				}
+				catch (IOException ex) {
+					throw new IllegalStateException(ex);
+				}
+			}
+			return super.loadClass(name, resolve);
+		}
+
+		@Override
+		public boolean isClassReloadable(Class<?> clazz) {
+			return clazz.getName().contains("MyConfig");
+		}
+	}
+
+}