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.messaging.handler;
018
019import org.springframework.lang.Nullable;
020import org.springframework.messaging.Message;
021
022/**
023 * Contract for mapping conditions to messages.
024 *
025 * <p>Message conditions can be combined (e.g. type + method-level conditions),
026 * matched to a specific Message, as well as compared to each other in the
027 * context of a Message to determine which one matches a request more closely.
028 *
029 * @author Rossen Stoyanchev
030 * @since 4.0
031 * @param <T> the kind of condition that this condition can be combined with or compared to
032 */
033public interface MessageCondition<T> {
034
035        /**
036         * Define the rules for combining this condition with another.
037         * For example combining type- and method-level conditions.
038         * @param other the condition to combine with
039         * @return the resulting message condition
040         */
041        T combine(T other);
042
043        /**
044         * Check if this condition matches the given Message and returns a
045         * potentially new condition with content tailored to the current message.
046         * For example a condition with destination patterns might return a new
047         * condition with sorted, matching patterns only.
048         * @return a condition instance in case of a match; or {@code null} if there is no match.
049         */
050        @Nullable
051        T getMatchingCondition(Message<?> message);
052
053        /**
054         * Compare this condition to another in the context of a specific message.
055         * It is assumed both instances have been obtained via
056         * {@link #getMatchingCondition(Message)} to ensure they have content
057         * relevant to current message only.
058         */
059        int compareTo(T other, Message<?> message);
060
061}