Consistently register CGLIB hints for lazy resolution proxy classes

Core JDK/CGLIB proxy registration code extracted to ClassHintUtils.

Closes gh-29584

spring-core/src/main/java/org/springframework/aot/hint/support/ClassHintUtils.java

@@ -0,0 +1,76 @@
+/*
+ * 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.aot.hint.support;
+
+import java.lang.reflect.Proxy;
+import java.util.function.Consumer;
+
+import org.springframework.aot.hint.MemberCategory;
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.TypeHint;
+import org.springframework.util.ClassUtils;
+
+/**
+ * Utilities for core hint inference on Spring-managed classes,
+ * specifically for proxy types such as interface-based JDK proxies
+ * and CGLIB-generated subclasses which need proxy/reflection hints.
+ *
+ * <p>Note that this class does not take specifics of Spring AOP or
+ * any other framework arrangement into account. It just operates
+ * on the JDK and CGLIB proxy facilities and their core conventions.
+ *
+ * @author Juergen Hoeller
+ * @since 6.0.3
+ * @see org.springframework.aot.hint.ProxyHints
+ * @see org.springframework.aot.hint.ReflectionHints
+ */
+public abstract class ClassHintUtils {
+
+	private static final Consumer<TypeHint.Builder> asClassBasedProxy = hint ->
+			hint.withMembers(MemberCategory.INVOKE_DECLARED_CONSTRUCTORS,
+					MemberCategory.INVOKE_DECLARED_METHODS,
+					MemberCategory.DECLARED_FIELDS);
+
+	private static final Consumer<TypeHint.Builder> asProxiedUserClass = hint ->
+			hint.withMembers(MemberCategory.INVOKE_PUBLIC_METHODS);
+
+
+	/**
+	 * Register a proxy hint for a JDK proxy or corresponding reflection hints
+	 * for a CGLIB-generated subclass, if necessary.
+	 * @param candidateClass the class to introspect
+	 * @param runtimeHints the RuntimeHints instance to register the hints on
+	 * @see Proxy#isProxyClass(Class)
+	 * @see ClassUtils#getUserClass(Class)
+	 */
+	public static void registerProxyIfNecessary(Class<?> candidateClass, RuntimeHints runtimeHints) {
+		if (Proxy.isProxyClass(candidateClass)) {
+			// A JDK proxy class needs an explicit hint
+			runtimeHints.proxies().registerJdkProxy(candidateClass.getInterfaces());
+		}
+		else {
+			// Potentially a CGLIB-generated subclass with reflection hints
+			Class<?> userClass = ClassUtils.getUserClass(candidateClass);
+			if (userClass != candidateClass) {
+				runtimeHints.reflection()
+						.registerType(candidateClass, asClassBasedProxy)
+						.registerType(userClass, asProxiedUserClass);
+			}
+		}
+	}
+
+}