org.springframework.http.codec.EncoderHttpMessageWriter Maven / Gradle / Ivy
/*
* Copyright 2002-2018 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.http.codec;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.reactivestreams.Publisher;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import org.springframework.core.ResolvableType;
import org.springframework.core.codec.Encoder;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ReactiveHttpOutputMessage;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* {@code HttpMessageWriter} that wraps and delegates to a {@link Encoder}.
*
* Also a {@code HttpMessageWriter} that pre-resolves encoding hints
* from the extra information available on the server side such as the request
* or controller method annotations.
*
* @author Arjen Poutsma
* @author Sebastien Deleuze
* @author Rossen Stoyanchev
* @since 5.0
*/
public class EncoderHttpMessageWriter implements HttpMessageWriter {
private final Encoder encoder;
private final List mediaTypes;
@Nullable
private final MediaType defaultMediaType;
/**
* Create an instance wrapping the given {@link Encoder}.
*/
public EncoderHttpMessageWriter(Encoder encoder) {
Assert.notNull(encoder, "Encoder is required");
this.encoder = encoder;
this.mediaTypes = MediaType.asMediaTypes(encoder.getEncodableMimeTypes());
this.defaultMediaType = initDefaultMediaType(this.mediaTypes);
}
@Nullable
private static MediaType initDefaultMediaType(List mediaTypes) {
return mediaTypes.stream().filter(MediaType::isConcrete).findFirst().orElse(null);
}
/**
* Return the {@code Encoder} of this writer.
*/
public Encoder getEncoder() {
return this.encoder;
}
@Override
public List getWritableMediaTypes() {
return this.mediaTypes;
}
@Override
public boolean canWrite(ResolvableType elementType, @Nullable MediaType mediaType) {
return this.encoder.canEncode(elementType, mediaType);
}
@SuppressWarnings("unchecked")
@Override
public Mono write(Publisher inputStream, ResolvableType elementType,
@Nullable MediaType mediaType, ReactiveHttpOutputMessage message, Map hints) {
MediaType contentType = updateContentType(message, mediaType);
HttpHeaders headers = message.getHeaders();
if (headers.getContentLength() < 0 && !headers.containsKey(HttpHeaders.TRANSFER_ENCODING)) {
if (inputStream instanceof Mono) {
// This works because we don't actually commit until after the first signal...
inputStream = ((Mono) inputStream).doOnNext(data -> {
Long contentLength = this.encoder.getContentLength(data, contentType);
if (contentLength != null) {
headers.setContentLength(contentLength);
}
});
}
}
Flux body = this.encoder.encode(
inputStream, message.bufferFactory(), elementType, contentType, hints);
return (isStreamingMediaType(contentType) ?
message.writeAndFlushWith(body.map(Flux::just)) : message.writeWith(body));
}
@Nullable
private MediaType updateContentType(ReactiveHttpOutputMessage message, @Nullable MediaType mediaType) {
MediaType result = message.getHeaders().getContentType();
if (result != null) {
return result;
}
MediaType fallback = this.defaultMediaType;
result = (useFallback(mediaType, fallback) ? fallback : mediaType);
if (result != null) {
result = addDefaultCharset(result, fallback);
message.getHeaders().setContentType(result);
}
return result;
}
private static boolean useFallback(@Nullable MediaType main, @Nullable MediaType fallback) {
return (main == null || !main.isConcrete() ||
main.equals(MediaType.APPLICATION_OCTET_STREAM) && fallback != null);
}
private static MediaType addDefaultCharset(MediaType main, @Nullable MediaType defaultType) {
if (main.getCharset() == null && defaultType != null && defaultType.getCharset() != null) {
return new MediaType(main, defaultType.getCharset());
}
return main;
}
private boolean isStreamingMediaType(@Nullable MediaType contentType) {
return (contentType != null && this.encoder instanceof HttpMessageEncoder &&
((HttpMessageEncoder) this.encoder).getStreamingMediaTypes().stream()
.anyMatch(contentType::isCompatibleWith));
}
// Server side only...
@Override
public Mono write(Publisher inputStream, ResolvableType actualType,
ResolvableType elementType, @Nullable MediaType mediaType, ServerHttpRequest request,
ServerHttpResponse response, Map hints) {
Map allHints = new HashMap<>();
allHints.putAll(getWriteHints(actualType, elementType, mediaType, request, response));
allHints.putAll(hints);
return write(inputStream, elementType, mediaType, response, allHints);
}
/**
* Get additional hints for encoding for example based on the server request
* or annotations from controller method parameters. By default, delegate to
* the encoder if it is an instance of {@link HttpMessageEncoder}.
*/
protected Map getWriteHints(ResolvableType streamType, ResolvableType elementType,
@Nullable MediaType mediaType, ServerHttpRequest request, ServerHttpResponse response) {
if (this.encoder instanceof HttpMessageEncoder) {
HttpMessageEncoder httpEncoder = (HttpMessageEncoder) this.encoder;
return httpEncoder.getEncodeHints(streamType, elementType, mediaType, request, response);
}
return Collections.emptyMap();
}
}