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/*
* Copyright 2002-2021 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
*
* https://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.List;
import java.util.Map;
import org.reactivestreams.Publisher;
import reactor.core.publisher.Mono;
import org.springframework.core.MethodParameter;
import org.springframework.core.ResolvableType;
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;
/**
* Strategy for encoding a stream of objects of type {@code } and writing
* the encoded stream of bytes to an {@link ReactiveHttpOutputMessage}.
*
* @author Rossen Stoyanchev
* @author Arjen Poutsma
* @author Sebastien Deleuze
* @since 5.0
* @param the type of objects in the input stream
*/
public interface HttpMessageWriter {
/**
* Return the list of media types supported by this Writer. The list may not
* apply to every possible target element type and calls to this method should
* typically be guarded via {@link #canWrite(ResolvableType, MediaType)
* canWrite(elementType, null)}. The list may also exclude media types
* supported only for a specific element type. Alternatively, use
* {@link #getWritableMediaTypes(ResolvableType)} for a more precise list.
* @return the general list of supported media types
*/
List getWritableMediaTypes();
/**
* Return the list of media types supported by this Writer for the given type
* of element. This list may differ from {@link #getWritableMediaTypes()}
* if the Writer doesn't support the element type, or if it supports it
* only for a subset of media types.
* @param elementType the type of element to encode
* @return the list of media types supported for the given class
* @since 5.3.4
*/
default List getWritableMediaTypes(ResolvableType elementType) {
return (canWrite(elementType, null) ? getWritableMediaTypes() : Collections.emptyList());
}
/**
* Whether the given object type is supported by this writer.
* @param elementType the type of object to check
* @param mediaType the media type for the write (possibly {@code null})
* @return {@code true} if writable, {@code false} otherwise
*/
boolean canWrite(ResolvableType elementType, @Nullable MediaType mediaType);
/**
* Write a given stream of object to the output message.
* @param inputStream the objects to write
* @param elementType the type of objects in the stream which must have been
* previously checked via {@link #canWrite(ResolvableType, MediaType)}
* @param mediaType the content type for the write (possibly {@code null} to
* indicate that the default content type of the writer must be used)
* @param message the message to write to
* @param hints additional information about how to encode and write
* @return indicates completion or error
*/
Mono write(Publisher inputStream, ResolvableType elementType,
@Nullable MediaType mediaType, ReactiveHttpOutputMessage message, Map hints);
/**
* Server-side only alternative to
* {@link #write(Publisher, ResolvableType, MediaType, ReactiveHttpOutputMessage, Map)}
* with additional context available.
* @param actualType the actual return type of the method that returned the
* value; for annotated controllers, the {@link MethodParameter} can be
* accessed via {@link ResolvableType#getSource()}.
* @param elementType the type of Objects in the input stream
* @param mediaType the content type to use (possibly {@code null} indicating
* the default content type of the writer should be used)
* @param request the current request
* @param response the current response
* @return a {@link Mono} that indicates completion of writing or error
*/
default Mono write(Publisher inputStream, ResolvableType actualType,
ResolvableType elementType, @Nullable MediaType mediaType, ServerHttpRequest request,
ServerHttpResponse response, Map hints) {
return write(inputStream, elementType, mediaType, response, hints);
}
}