001/*
002 * Copyright 2002-2019 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.core.annotation;
018
019import java.lang.annotation.Annotation;
020
021/**
022 * Strategy interface used to select between two {@link MergedAnnotation}
023 * instances.
024 *
025 * @author Phillip Webb
026 * @since 5.2
027 * @param <A> the annotation type
028 * @see MergedAnnotationSelectors
029 */
030@FunctionalInterface
031public interface MergedAnnotationSelector<A extends Annotation> {
032
033        /**
034         * Determine if the existing annotation is known to be the best
035         * candidate and any subsequent selections may be skipped.
036         * @param annotation the annotation to check
037         * @return {@code true} if the annotation is known to be the best candidate
038         */
039        default boolean isBestCandidate(MergedAnnotation<A> annotation) {
040                return false;
041        }
042
043        /**
044         * Select the annotation that should be used.
045         * @param existing an existing annotation returned from an earlier result
046         * @param candidate a candidate annotation that may be better suited
047         * @return the most appropriate annotation from the {@code existing} or
048         * {@code candidate}
049         */
050        MergedAnnotation<A> select(MergedAnnotation<A> existing, MergedAnnotation<A> candidate);
051
052}