001/*
002 * Copyright 2002-2020 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.rsocket.annotation.support;
018
019import io.rsocket.RSocket;
020import reactor.core.publisher.Mono;
021
022import org.springframework.core.MethodParameter;
023import org.springframework.messaging.Message;
024import org.springframework.messaging.handler.invocation.reactive.HandlerMethodArgumentResolver;
025import org.springframework.messaging.rsocket.RSocketRequester;
026import org.springframework.util.Assert;
027
028/**
029 * Resolves arguments of type {@link RSocket} that can be used for making
030 * requests to the remote peer.
031 *
032 * @author Rossen Stoyanchev
033 * @since 5.2
034 */
035public class RSocketRequesterMethodArgumentResolver implements HandlerMethodArgumentResolver {
036
037        /**
038         * Message header name that is expected to have the {@link RSocket} to
039         * initiate new interactions to the remote peer with.
040         */
041        public static final String RSOCKET_REQUESTER_HEADER = "rsocketRequester";
042
043
044        @Override
045        public boolean supportsParameter(MethodParameter parameter) {
046                Class<?> type = parameter.getParameterType();
047                return (RSocketRequester.class.equals(type) || RSocket.class.isAssignableFrom(type));
048        }
049
050        @Override
051        public Mono<Object> resolveArgument(MethodParameter parameter, Message<?> message) {
052                Object headerValue = message.getHeaders().get(RSOCKET_REQUESTER_HEADER);
053                Assert.notNull(headerValue, "Missing '" + RSOCKET_REQUESTER_HEADER + "'");
054
055                Assert.isInstanceOf(RSocketRequester.class, headerValue, "Expected header value of type RSocketRequester");
056                RSocketRequester requester = (RSocketRequester) headerValue;
057
058                Class<?> type = parameter.getParameterType();
059                if (RSocketRequester.class.equals(type)) {
060                        return Mono.just(requester);
061                }
062                else if (RSocket.class.isAssignableFrom(type)) {
063                        return Mono.justOrEmpty(requester.rsocket());
064                }
065                else {
066                        return Mono.error(new IllegalArgumentException("Unexpected parameter type: " + parameter));
067                }
068        }
069
070}