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.http.codec.protobuf;
018
019import java.io.IOException;
020import java.util.Collections;
021import java.util.List;
022import java.util.Map;
023import java.util.stream.Collectors;
024
025import com.google.protobuf.Message;
026import org.reactivestreams.Publisher;
027import reactor.core.publisher.Flux;
028import reactor.core.publisher.Mono;
029
030import org.springframework.core.ResolvableType;
031import org.springframework.core.io.buffer.DataBuffer;
032import org.springframework.core.io.buffer.DataBufferFactory;
033import org.springframework.core.io.buffer.DataBufferUtils;
034import org.springframework.http.MediaType;
035import org.springframework.http.codec.HttpMessageEncoder;
036import org.springframework.lang.Nullable;
037import org.springframework.util.MimeType;
038
039/**
040 * An {@code Encoder} that writes {@link com.google.protobuf.Message}s
041 * using <a href="https://developers.google.com/protocol-buffers/">Google Protocol Buffers</a>.
042 *
043 * <p>Flux are serialized using
044 * <a href="https://developers.google.com/protocol-buffers/docs/techniques?hl=en#streaming">delimited Protobuf messages</a>
045 * with the size of each message specified before the message itself. Single values are
046 * serialized using regular Protobuf message format (without the size prepended before the message).
047 *
048 * <p>To generate {@code Message} Java classes, you need to install the {@code protoc} binary.
049 *
050 * <p>This encoder requires Protobuf 3 or higher, and supports
051 * {@code "application/x-protobuf"} and {@code "application/octet-stream"} with the official
052 * {@code "com.google.protobuf:protobuf-java"} library.
053 *
054 * @author S茅bastien Deleuze
055 * @since 5.1
056 * @see ProtobufDecoder
057 */
058public class ProtobufEncoder extends ProtobufCodecSupport implements HttpMessageEncoder<Message> {
059
060        private static final List<MediaType> streamingMediaTypes = MIME_TYPES
061                        .stream()
062                        .map(mimeType -> new MediaType(mimeType.getType(), mimeType.getSubtype(),
063                                        Collections.singletonMap(DELIMITED_KEY, DELIMITED_VALUE)))
064                        .collect(Collectors.toList());
065
066
067        @Override
068        public boolean canEncode(ResolvableType elementType, @Nullable MimeType mimeType) {
069                return Message.class.isAssignableFrom(elementType.toClass()) && supportsMimeType(mimeType);
070        }
071
072        @Override
073        public Flux<DataBuffer> encode(Publisher<? extends Message> inputStream, DataBufferFactory bufferFactory,
074                        ResolvableType elementType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
075
076                return Flux.from(inputStream).map(message ->
077                                encodeValue(message, bufferFactory, !(inputStream instanceof Mono)));
078        }
079
080        @Override
081        public DataBuffer encodeValue(Message message, DataBufferFactory bufferFactory,
082                        ResolvableType valueType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
083
084                return encodeValue(message, bufferFactory, false);
085        }
086
087        private DataBuffer encodeValue(Message message, DataBufferFactory bufferFactory, boolean delimited) {
088
089                DataBuffer buffer = bufferFactory.allocateBuffer();
090                boolean release = true;
091                try {
092                        if (delimited) {
093                                message.writeDelimitedTo(buffer.asOutputStream());
094                        }
095                        else {
096                                message.writeTo(buffer.asOutputStream());
097                        }
098                        release = false;
099                        return buffer;
100                }
101                catch (IOException ex) {
102                        throw new IllegalStateException("Unexpected I/O error while writing to data buffer", ex);
103                }
104                finally {
105                        if (release) {
106                                DataBufferUtils.release(buffer);
107                        }
108                }
109        }
110
111        @Override
112        public List<MediaType> getStreamingMediaTypes() {
113                return streamingMediaTypes;
114        }
115
116        @Override
117        public List<MimeType> getEncodableMimeTypes() {
118                return getMimeTypes();
119        }
120
121}