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.messaging.handler.invocation;
018
019import java.util.ArrayList;
020import java.util.Collections;
021import java.util.List;
022
023import org.apache.commons.logging.Log;
024import org.apache.commons.logging.LogFactory;
025
026import org.springframework.core.MethodParameter;
027import org.springframework.lang.Nullable;
028import org.springframework.messaging.Message;
029import org.springframework.util.concurrent.ListenableFuture;
030
031/**
032 * A HandlerMethodReturnValueHandler that wraps and delegates to others.
033 *
034 * @author Rossen Stoyanchev
035 * @since 4.0
036 */
037public class HandlerMethodReturnValueHandlerComposite implements AsyncHandlerMethodReturnValueHandler {
038
039        /** Public for wrapping with fallback logger. */
040        public static final Log defaultLogger = LogFactory.getLog(HandlerMethodReturnValueHandlerComposite.class);
041
042
043        private Log logger = defaultLogger;
044
045        private final List<HandlerMethodReturnValueHandler> returnValueHandlers = new ArrayList<>();
046
047
048        /**
049         * Set an alternative logger to use than the one based on the class name.
050         * @param logger the logger to use
051         * @since 5.1
052         */
053        public void setLogger(Log logger) {
054                this.logger = logger;
055        }
056
057        /**
058         * Return the currently configured Logger.
059         * @since 5.1
060         */
061        public Log getLogger() {
062                return logger;
063        }
064
065        /**
066         * Return a read-only list with the configured handlers.
067         */
068        public List<HandlerMethodReturnValueHandler> getReturnValueHandlers() {
069                return Collections.unmodifiableList(this.returnValueHandlers);
070        }
071
072        /**
073         * Clear the list of configured handlers.
074         */
075        public void clear() {
076                this.returnValueHandlers.clear();
077        }
078
079        /**
080         * Add the given {@link HandlerMethodReturnValueHandler}.
081         */
082        public HandlerMethodReturnValueHandlerComposite addHandler(HandlerMethodReturnValueHandler returnValueHandler) {
083                this.returnValueHandlers.add(returnValueHandler);
084                return this;
085        }
086
087        /**
088         * Add the given {@link HandlerMethodReturnValueHandler HandlerMethodReturnValueHandlers}.
089         */
090        public HandlerMethodReturnValueHandlerComposite addHandlers(
091                        @Nullable List<? extends HandlerMethodReturnValueHandler> handlers) {
092
093                if (handlers != null) {
094                        this.returnValueHandlers.addAll(handlers);
095                }
096                return this;
097        }
098
099        @Override
100        public boolean supportsReturnType(MethodParameter returnType) {
101                return getReturnValueHandler(returnType) != null;
102        }
103
104        @SuppressWarnings("ForLoopReplaceableByForEach")
105        @Nullable
106        private HandlerMethodReturnValueHandler getReturnValueHandler(MethodParameter returnType) {
107                for (int i = 0; i < this.returnValueHandlers.size(); i++) {
108                        HandlerMethodReturnValueHandler handler = this.returnValueHandlers.get(i);
109                        if (handler.supportsReturnType(returnType)) {
110                                return handler;
111                        }
112                }
113                return null;
114        }
115
116        @Override
117        public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType, Message<?> message)
118                        throws Exception {
119
120                HandlerMethodReturnValueHandler handler = getReturnValueHandler(returnType);
121                if (handler == null) {
122                        throw new IllegalStateException("No handler for return value type: " + returnType.getParameterType());
123                }
124                if (logger.isTraceEnabled()) {
125                        logger.trace("Processing return value with " + handler);
126                }
127                handler.handleReturnValue(returnValue, returnType, message);
128        }
129
130        @Override
131        public boolean isAsyncReturnValue(Object returnValue, MethodParameter returnType) {
132                HandlerMethodReturnValueHandler handler = getReturnValueHandler(returnType);
133                return (handler instanceof AsyncHandlerMethodReturnValueHandler &&
134                                ((AsyncHandlerMethodReturnValueHandler) handler).isAsyncReturnValue(returnValue, returnType));
135        }
136
137        @Override
138        @Nullable
139        public ListenableFuture<?> toListenableFuture(Object returnValue, MethodParameter returnType) {
140                HandlerMethodReturnValueHandler handler = getReturnValueHandler(returnType);
141                if (handler instanceof AsyncHandlerMethodReturnValueHandler) {
142                        return ((AsyncHandlerMethodReturnValueHandler) handler).toListenableFuture(returnValue, returnType);
143                }
144                return null;
145        }
146
147}