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.reflect.AnnotatedElement; 020import java.util.Arrays; 021import java.util.List; 022 023import org.springframework.core.DecoratingProxy; 024import org.springframework.core.OrderComparator; 025import org.springframework.core.annotation.MergedAnnotations.SearchStrategy; 026import org.springframework.lang.Nullable; 027 028/** 029 * {@code AnnotationAwareOrderComparator} is an extension of 030 * {@link OrderComparator} that supports Spring's 031 * {@link org.springframework.core.Ordered} interface as well as the 032 * {@link Order @Order} and {@link javax.annotation.Priority @Priority} 033 * annotations, with an order value provided by an {@code Ordered} 034 * instance overriding a statically defined annotation value (if any). 035 * 036 * <p>Consult the Javadoc for {@link OrderComparator} for details on the 037 * sort semantics for non-ordered objects. 038 * 039 * @author Juergen Hoeller 040 * @author Oliver Gierke 041 * @author Stephane Nicoll 042 * @since 2.0.1 043 * @see org.springframework.core.Ordered 044 * @see org.springframework.core.annotation.Order 045 * @see javax.annotation.Priority 046 */ 047public class AnnotationAwareOrderComparator extends OrderComparator { 048 049 /** 050 * Shared default instance of {@code AnnotationAwareOrderComparator}. 051 */ 052 public static final AnnotationAwareOrderComparator INSTANCE = new AnnotationAwareOrderComparator(); 053 054 055 /** 056 * This implementation checks for {@link Order @Order} or 057 * {@link javax.annotation.Priority @Priority} on various kinds of 058 * elements, in addition to the {@link org.springframework.core.Ordered} 059 * check in the superclass. 060 */ 061 @Override 062 @Nullable 063 protected Integer findOrder(Object obj) { 064 Integer order = super.findOrder(obj); 065 if (order != null) { 066 return order; 067 } 068 return findOrderFromAnnotation(obj); 069 } 070 071 @Nullable 072 private Integer findOrderFromAnnotation(Object obj) { 073 AnnotatedElement element = (obj instanceof AnnotatedElement ? (AnnotatedElement) obj : obj.getClass()); 074 MergedAnnotations annotations = MergedAnnotations.from(element, SearchStrategy.TYPE_HIERARCHY); 075 Integer order = OrderUtils.getOrderFromAnnotations(element, annotations); 076 if (order == null && obj instanceof DecoratingProxy) { 077 return findOrderFromAnnotation(((DecoratingProxy) obj).getDecoratedClass()); 078 } 079 return order; 080 } 081 082 /** 083 * This implementation retrieves an @{@link javax.annotation.Priority} 084 * value, allowing for additional semantics over the regular @{@link Order} 085 * annotation: typically, selecting one object over another in case of 086 * multiple matches but only one object to be returned. 087 */ 088 @Override 089 @Nullable 090 public Integer getPriority(Object obj) { 091 if (obj instanceof Class) { 092 return OrderUtils.getPriority((Class<?>) obj); 093 } 094 Integer priority = OrderUtils.getPriority(obj.getClass()); 095 if (priority == null && obj instanceof DecoratingProxy) { 096 return getPriority(((DecoratingProxy) obj).getDecoratedClass()); 097 } 098 return priority; 099 } 100 101 102 /** 103 * Sort the given list with a default {@link AnnotationAwareOrderComparator}. 104 * <p>Optimized to skip sorting for lists with size 0 or 1, 105 * in order to avoid unnecessary array extraction. 106 * @param list the List to sort 107 * @see java.util.List#sort(java.util.Comparator) 108 */ 109 public static void sort(List<?> list) { 110 if (list.size() > 1) { 111 list.sort(INSTANCE); 112 } 113 } 114 115 /** 116 * Sort the given array with a default AnnotationAwareOrderComparator. 117 * <p>Optimized to skip sorting for lists with size 0 or 1, 118 * in order to avoid unnecessary array extraction. 119 * @param array the array to sort 120 * @see java.util.Arrays#sort(Object[], java.util.Comparator) 121 */ 122 public static void sort(Object[] array) { 123 if (array.length > 1) { 124 Arrays.sort(array, INSTANCE); 125 } 126 } 127 128 /** 129 * Sort the given array or List with a default AnnotationAwareOrderComparator, 130 * if necessary. Simply skips sorting when given any other value. 131 * <p>Optimized to skip sorting for lists with size 0 or 1, 132 * in order to avoid unnecessary array extraction. 133 * @param value the array or List to sort 134 * @see java.util.Arrays#sort(Object[], java.util.Comparator) 135 */ 136 public static void sortIfNecessary(Object value) { 137 if (value instanceof Object[]) { 138 sort((Object[]) value); 139 } 140 else if (value instanceof List) { 141 sort((List<?>) value); 142 } 143 } 144 145}