Integrate class proxy generation in AOT processing

This commit updates ApplicationContextAotGenerator to register a
handler that process Cglib generated classes. The handler registers
such classes to the GeneratedFiles and provide a hint so that it
can be instantiated using reflection.

Closes gh-28954

spring-context/src/main/java/org/springframework/context/aot/ApplicationContextAotGenerator.java

@@ -16,9 +16,12 @@
 
 package org.springframework.context.aot;
 
+import java.util.function.Supplier;
+
 import org.springframework.aot.generate.GenerationContext;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.cglib.core.ReflectUtils;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextInitializer;
 import org.springframework.context.support.GenericApplicationContext;
@@ -47,12 +50,24 @@ public class ApplicationContextAotGenerator {
 	 */
 	public ClassName processAheadOfTime(GenericApplicationContext applicationContext,
 			GenerationContext generationContext) {
-		applicationContext.refreshForAotProcessing();
-		DefaultListableBeanFactory beanFactory = applicationContext.getDefaultListableBeanFactory();
-		ApplicationContextInitializationCodeGenerator codeGenerator =
-				new ApplicationContextInitializationCodeGenerator(generationContext);
-		new BeanFactoryInitializationAotContributions(beanFactory).applyTo(generationContext, codeGenerator);
-		return codeGenerator.getGeneratedClass().getName();
+		return withGeneratedClassHandler(new GeneratedClassHandler(generationContext), () -> {
+			applicationContext.refreshForAotProcessing();
+			DefaultListableBeanFactory beanFactory = applicationContext.getDefaultListableBeanFactory();
+			ApplicationContextInitializationCodeGenerator codeGenerator =
+					new ApplicationContextInitializationCodeGenerator(generationContext);
+			new BeanFactoryInitializationAotContributions(beanFactory).applyTo(generationContext, codeGenerator);
+			return codeGenerator.getGeneratedClass().getName();
+		});
+	}
+
+	private <T> T withGeneratedClassHandler(GeneratedClassHandler generatedClassHandler, Supplier<T> task) {
+		try {
+			ReflectUtils.setGeneratedClassHandler(generatedClassHandler);
+			return task.get();
+		}
+		finally {
+			ReflectUtils.setGeneratedClassHandler(null);
+		}
 	}
 
 }

spring-context/src/main/java/org/springframework/context/aot/GeneratedClassHandler.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2002-2022 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.aot;
+
+import java.util.function.BiConsumer;
+import java.util.function.Consumer;
+
+import org.springframework.aot.generate.GeneratedFiles;
+import org.springframework.aot.generate.GeneratedFiles.Kind;
+import org.springframework.aot.generate.GenerationContext;
+import org.springframework.aot.hint.MemberCategory;
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.TypeHint.Builder;
+import org.springframework.aot.hint.TypeReference;
+import org.springframework.cglib.core.ReflectUtils;
+import org.springframework.core.io.ByteArrayResource;
+
+/**
+ * Handle generated classes by adding them to a {@link GenerationContext},
+ * and register the necessary hints so that they can be instantiated.
+ *
+ * @author Stephane Nicoll
+ * @see ReflectUtils#setGeneratedClassHandler(BiConsumer)
+ */
+class GeneratedClassHandler implements BiConsumer<String, byte[]> {
+
+	private static final Consumer<Builder> asCglibProxy = hint ->
+			hint.withMembers(MemberCategory.INVOKE_DECLARED_CONSTRUCTORS);
+
+	private final RuntimeHints runtimeHints;
+
+	private final GeneratedFiles generatedFiles;
+
+	GeneratedClassHandler(GenerationContext generationContext) {
+		this.runtimeHints = generationContext.getRuntimeHints();
+		this.generatedFiles = generationContext.getGeneratedFiles();
+	}
+
+	@Override
+	public void accept(String className, byte[] content) {
+		this.runtimeHints.reflection().registerType(TypeReference.of(className), asCglibProxy);
+		String path = className.replace(".", "/") + ".class";
+		this.generatedFiles.addFile(Kind.CLASS, path, new ByteArrayResource(content));
+	}
+
+}