001/*
002 * Copyright 2002-2017 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.invocation.reactive;
018
019import reactor.core.publisher.Mono;
020
021import org.springframework.core.MethodParameter;
022import org.springframework.lang.Nullable;
023import org.springframework.messaging.Message;
024
025/**
026 * Handle the return value from the invocation of an annotated {@link Message}
027 * handling method.
028 *
029 * @author Rossen Stoyanchev
030 * @since 5.2
031 */
032public interface HandlerMethodReturnValueHandler {
033
034        /** Header containing a DataBufferFactory for use in return value handling. */
035        String DATA_BUFFER_FACTORY_HEADER = "dataBufferFactory";
036
037
038        /**
039         * Whether the given {@linkplain MethodParameter method return type} is
040         * supported by this handler.
041         * @param returnType the method return type to check
042         * @return {@code true} if this handler supports the supplied return type;
043         * {@code false} otherwise
044         */
045        boolean supportsReturnType(MethodParameter returnType);
046
047        /**
048         * Handle the given return value.
049         * @param returnValue the value returned from the handler method
050         * @param returnType the type of the return value. This type must have previously
051         * been passed to {@link #supportsReturnType(MethodParameter)}
052         * and it must have returned {@code true}.
053         * @return {@code Mono<Void>} to indicate when handling is complete.
054         */
055        Mono<Void> handleReturnValue(@Nullable Object returnValue, MethodParameter returnType, Message<?> message);
056
057}