org.springframework.core.codec.Decoder Maven / Gradle / Ivy
/*
* Copyright 2002-2019 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.core.codec;
import java.util.List;
import java.util.Map;
import org.reactivestreams.Publisher;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.core.publisher.MonoProcessor;
import org.springframework.core.ResolvableType;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.MimeType;
/**
* Strategy for decoding a {@link DataBuffer} input stream into an output stream
* of elements of type {@code }.
*
* @author Sebastien Deleuze
* @author Rossen Stoyanchev
* @since 5.0
* @param the type of elements in the output stream
*/
public interface Decoder {
/**
* Whether the decoder supports the given target element type and the MIME
* type of the source stream.
* @param elementType the target element type for the output stream
* @param mimeType the mime type associated with the stream to decode
* (can be {@code null} if not specified)
* @return {@code true} if supported, {@code false} otherwise
*/
boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType);
/**
* Decode a {@link DataBuffer} input stream into a Flux of {@code T}.
* @param inputStream the {@code DataBuffer} input stream to decode
* @param elementType the expected type of elements in the output stream;
* this type must have been previously passed to the {@link #canDecode}
* method and it must have returned {@code true}.
* @param mimeType the MIME type associated with the input stream (optional)
* @param hints additional information about how to do encode
* @return the output stream with decoded elements
*/
Flux decode(Publisher inputStream, ResolvableType elementType,
@Nullable MimeType mimeType, @Nullable Map hints);
/**
* Decode a {@link DataBuffer} input stream into a Mono of {@code T}.
* @param inputStream the {@code DataBuffer} input stream to decode
* @param elementType the expected type of elements in the output stream;
* this type must have been previously passed to the {@link #canDecode}
* method and it must have returned {@code true}.
* @param mimeType the MIME type associated with the input stream (optional)
* @param hints additional information about how to do encode
* @return the output stream with the decoded element
*/
Mono decodeToMono(Publisher inputStream, ResolvableType elementType,
@Nullable MimeType mimeType, @Nullable Map hints);
/**
* Decode a data buffer to an Object of type T. This is useful when the input
* stream consists of discrete messages (or events) and the content for each
* can be decoded on its own.
* @param buffer the {@code DataBuffer} to decode
* @param targetType the expected output type
* @param mimeType the MIME type associated with the data
* @param hints additional information about how to do encode
* @return the decoded value, possibly {@code null}
* @since 5.2
*/
@Nullable
default T decode(DataBuffer buffer, ResolvableType targetType,
@Nullable MimeType mimeType, @Nullable Map hints) throws DecodingException {
MonoProcessor processor = MonoProcessor.create();
decodeToMono(Mono.just(buffer), targetType, mimeType, hints).subscribeWith(processor);
Assert.state(processor.isTerminated(), "DataBuffer decoding should have completed.");
Throwable ex = processor.getError();
if (ex != null) {
throw (ex instanceof CodecException ? (CodecException) ex :
new DecodingException("Failed to decode: " + ex.getMessage(), ex));
}
return processor.peek();
}
/**
* Return the list of MIME types this decoder supports.
*/
List getDecodableMimeTypes();
}