org.springframework.core.annotation.MergedAnnotationSelectors Maven / Gradle / Ivy
/*
* Copyright 2002-2019 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.core.annotation;
import java.lang.annotation.Annotation;
import java.util.function.Predicate;
/**
* {@link MergedAnnotationSelector} implementations that provide various options
* for {@link MergedAnnotation} instances.
*
* @author Phillip Webb
* @since 5.2
* @see MergedAnnotations#get(Class, Predicate, MergedAnnotationSelector)
* @see MergedAnnotations#get(String, Predicate, MergedAnnotationSelector)
*/
public abstract class MergedAnnotationSelectors {
private static final MergedAnnotationSelector NEAREST = new Nearest();
private static final MergedAnnotationSelector FIRST_DIRECTLY_DECLARED = new FirstDirectlyDeclared();
private MergedAnnotationSelectors() {
}
/**
* Select the nearest annotation, i.e. the one with the lowest distance.
* @return a selector that picks the annotation with the lowest distance
*/
@SuppressWarnings("unchecked")
public static MergedAnnotationSelector nearest() {
return (MergedAnnotationSelector) NEAREST;
}
/**
* Select the first directly declared annotation when possible. If no direct
* annotations are declared then the nearest annotation is selected.
* @return a selector that picks the first directly declared annotation whenever possible
*/
@SuppressWarnings("unchecked")
public static MergedAnnotationSelector firstDirectlyDeclared() {
return (MergedAnnotationSelector) FIRST_DIRECTLY_DECLARED;
}
/**
* {@link MergedAnnotationSelector} to select the nearest annotation.
*/
private static class Nearest implements MergedAnnotationSelector {
@Override
public boolean isBestCandidate(MergedAnnotation annotation) {
return annotation.getDistance() == 0;
}
@Override
public MergedAnnotation select(
MergedAnnotation existing, MergedAnnotation candidate) {
if (candidate.getDistance() < existing.getDistance()) {
return candidate;
}
return existing;
}
}
/**
* {@link MergedAnnotationSelector} to select the first directly declared
* annotation.
*/
private static class FirstDirectlyDeclared implements MergedAnnotationSelector {
@Override
public boolean isBestCandidate(MergedAnnotation annotation) {
return annotation.getDistance() == 0;
}
@Override
public MergedAnnotation select(
MergedAnnotation existing, MergedAnnotation candidate) {
if (existing.getDistance() > 0 && candidate.getDistance() == 0) {
return candidate;
}
return existing;
}
}
}