org.springframework.core.codec.Decoder.java Source code

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Here is the source code for org.springframework.core.codec.Decoder.java

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/*
 * Copyright 2002-2016 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 <T>}.
 *
 * @author Sebastien Deleuze
 * @author Rossen Stoyanchev
 * @since 5.0
 * @param <T> the type of elements in the output stream
 */
public interface Decoder<T> {

    /**
     * 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<T> decode(Publisher<DataBuffer> inputStream, ResolvableType elementType, @Nullable MimeType mimeType,
            @Nullable Map<String, Object> 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<T> decodeToMono(Publisher<DataBuffer> inputStream, ResolvableType elementType, @Nullable MimeType mimeType,
            @Nullable Map<String, Object> 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
     */
    @SuppressWarnings("ConstantConditions")
    default T decode(DataBuffer buffer, ResolvableType targetType, @Nullable MimeType mimeType,
            @Nullable Map<String, Object> hints) throws DecodingException {

        MonoProcessor<T> 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<MimeType> getDecodableMimeTypes();

}