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Library to support implementing representations for hyper-text driven REST web services.
There is a newer version: 2.4.0
/*
 * Copyright 2022-2023 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.hateoas.aot;

import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aot.hint.MemberCategory;
import org.springframework.aot.hint.ReflectionHints;
import org.springframework.core.ResolvableType;
import org.springframework.hateoas.CollectionModel;
import org.springframework.hateoas.EntityModel;
import org.springframework.http.HttpEntity;

/**
 * Some helper classes to register types for reflection.
 *
 * @author Oliver Drotbohm
 * @since 2.0
 */
class AotUtils {

	private static final Logger LOGGER = LoggerFactory.getLogger(AotUtils.class);
	private static final List> MODEL_TYPES = List.of(EntityModel.class, CollectionModel.class);
	private static final Set> SEEN_TYPES = new HashSet<>();

	/**
	 * Registers domain types held in {@link EntityModel} and {@link CollectionModel}s for reflection.
	 *
	 * @param type must not be {@literal null}.
	 * @param reflection must not be {@literal null}.
	 * @param context must not be {@literal null}.
	 */
	public static void registerModelDomainTypesForReflection(ResolvableType type, ReflectionHints reflection,
			Class context) {

		if (HttpEntity.class.isAssignableFrom(type.resolve(Object.class))) {
			registerModelDomainTypesForReflection(type.as(HttpEntity.class).getGeneric(0), reflection, context);
		}

		MODEL_TYPES.stream()
				.flatMap(it -> extractGenerics(it, type).stream())
				.forEach(it -> registerTypeForReflection(it, reflection, context));
	}

	/**
	 * Registers the given type for constructor and method invocation reflection.
	 *
	 * @param type must not be {@literal null}.
	 * @param reflection must not be {@literal null}.
	 * @param context must not be {@literal null}.
	 */
	public static void registerTypeForReflection(Class type, ReflectionHints reflection, Class context) {

		if (SEEN_TYPES.contains(type)) {
			return;
		}

		LOGGER.info("Registering {} for reflection (for {})", type.getName(), context.getName());

		reflection.registerType(type,
				MemberCategory.INVOKE_DECLARED_METHODS,
				MemberCategory.INTROSPECT_DECLARED_CONSTRUCTORS);

		SEEN_TYPES.add(type);
	}

	/**
	 * Extracts the generics from the given model type if the given {@link ResolvableType} is assignable.
	 *
	 * @param modelType must not be {@literal null}.
	 * @param type must not be {@literal null}.
	 * @return will never be {@literal null}.
	 */
	private static Optional> extractGenerics(Class modelType, ResolvableType type) {

		if (!modelType.isAssignableFrom(type.resolve(Object.class))) {
			return Optional.empty();
		}

		var unresolved = type.as(modelType).getGeneric(0);
		var resolved = unresolved.resolve();

		if (resolved == null) {
			return Optional.empty();
		}

		var nested = MODEL_TYPES.stream()
				.filter(it -> it.isAssignableFrom(resolved))
				.toList();

		// No nested matches -> return original
		if (nested.isEmpty()) {
			return Optional.of(resolved);
		}

		return nested.stream()
				.flatMap(it -> extractGenerics(it, unresolved).stream())
				.findFirst();
	}
}