001/*
002 * Copyright 2002-2015 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;
018
019/**
020 * {@code Ordered} is an interface that can be implemented by objects that
021 * should be <em>orderable</em>, for example in a {@code Collection}.
022 *
023 * <p>The actual {@link #getOrder() order} can be interpreted as prioritization,
024 * with the first object (with the lowest order value) having the highest
025 * priority.
026 *
027 * <p>Note that there is also a <em>priority</em> marker for this interface:
028 * {@link PriorityOrdered}. Order values expressed by {@code PriorityOrdered}
029 * objects always apply before same order values expressed by <em>plain</em>
030 * {@link Ordered} objects.
031 *
032 * <p>Consult the Javadoc for {@link OrderComparator} for details on the
033 * sort semantics for non-ordered objects.
034 *
035 * @author Juergen Hoeller
036 * @author Sam Brannen
037 * @since 07.04.2003
038 * @see PriorityOrdered
039 * @see OrderComparator
040 * @see org.springframework.core.annotation.Order
041 * @see org.springframework.core.annotation.AnnotationAwareOrderComparator
042 */
043public interface Ordered {
044
045        /**
046         * Useful constant for the highest precedence value.
047         * @see java.lang.Integer#MIN_VALUE
048         */
049        int HIGHEST_PRECEDENCE = Integer.MIN_VALUE;
050
051        /**
052         * Useful constant for the lowest precedence value.
053         * @see java.lang.Integer#MAX_VALUE
054         */
055        int LOWEST_PRECEDENCE = Integer.MAX_VALUE;
056
057
058        /**
059         * Get the order value of this object.
060         * <p>Higher values are interpreted as lower priority. As a consequence,
061         * the object with the lowest value has the highest priority (somewhat
062         * analogous to Servlet {@code load-on-startup} values).
063         * <p>Same order values will result in arbitrary sort positions for the
064         * affected objects.
065         * @return the order value
066         * @see #HIGHEST_PRECEDENCE
067         * @see #LOWEST_PRECEDENCE
068         */
069        int getOrder();
070
071}