feign.stream.StreamDecoder Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of feign-core Show documentation
feign-core
The newest version!
/**
 * Copyright 2012-2019 The Feign 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 feign.stream;

import feign.FeignException;
import feign.Response;
import feign.codec.Decoder;
import java.io.Closeable;
import java.io.IOException;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Iterator;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import static feign.Util.ensureClosed;

/**
 * Iterator based decoder that support streaming.
 * 
 * 

 * Example: 

 * 
 * 
 * 
 * Feign.builder()
 *   .decoder(StreamDecoder.create(JacksonIteratorDecoder.create()))
 *   .doNotCloseAfterDecode() // Required for streaming
 *   .target(GitHub.class, "https://api.github.com");
 * interface GitHub {
 *  {@literal @}RequestLine("GET /repos/{owner}/{repo}/contributors")
 *   Stream contributors(@Param("owner") String owner, @Param("repo") String repo);
 * }
 * 
 */
public final class StreamDecoder implements Decoder {

	private final Decoder iteratorDecoder;

	StreamDecoder(Decoder iteratorDecoder) {
		this.iteratorDecoder = iteratorDecoder;
	}

	@Override
	public Object decode(Response response, Type type) throws IOException, FeignException {
		if (!(type instanceof ParameterizedType)) {
			throw new IllegalArgumentException("StreamDecoder supports only stream: unknown " + type);
		}
		ParameterizedType streamType = (ParameterizedType) type;
		if (!Stream.class.equals(streamType.getRawType())) {
			throw new IllegalArgumentException("StreamDecoder supports only stream: unknown " + type);
		}
		Iterator iterator = (Iterator) iteratorDecoder.decode(response, new IteratorParameterizedType(streamType));

		return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, 0), false).onClose(() -> {
			if (iterator instanceof Closeable) {
				ensureClosed((Closeable) iterator);
			} else {
				ensureClosed(response);
			}
		});
	}

	public static StreamDecoder create(Decoder iteratorDecoder) {
		return new StreamDecoder(iteratorDecoder);
	}

	static final class IteratorParameterizedType implements ParameterizedType {

		private final ParameterizedType streamType;

		IteratorParameterizedType(ParameterizedType streamType) {
			this.streamType = streamType;
		}

		@Override
		public Type[] getActualTypeArguments() {
			return streamType.getActualTypeArguments();
		}

		@Override
		public Type getRawType() {
			return Iterator.class;
		}

		@Override
		public Type getOwnerType() {
			return null;
		}
	}
}