001/* 002 * Copyright 2002-2020 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.core.codec; 018 019import java.util.Map; 020 021import org.reactivestreams.Publisher; 022import reactor.core.publisher.Flux; 023 024import org.springframework.core.ResolvableType; 025import org.springframework.core.io.buffer.DataBuffer; 026import org.springframework.core.io.buffer.DataBufferFactory; 027import org.springframework.core.io.buffer.DataBufferUtils; 028import org.springframework.core.io.buffer.PooledDataBuffer; 029import org.springframework.lang.Nullable; 030import org.springframework.util.MimeType; 031 032/** 033 * Abstract base class for {@link org.springframework.core.codec.Encoder} 034 * classes that can only deal with a single value. 035 * 036 * @author Arjen Poutsma 037 * @since 5.0 038 * @param <T> the element type 039 */ 040public abstract class AbstractSingleValueEncoder<T> extends AbstractEncoder<T> { 041 042 043 public AbstractSingleValueEncoder(MimeType... supportedMimeTypes) { 044 super(supportedMimeTypes); 045 } 046 047 048 @Override 049 public final Flux<DataBuffer> encode(Publisher<? extends T> inputStream, DataBufferFactory bufferFactory, 050 ResolvableType elementType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) { 051 052 return Flux.from(inputStream) 053 .take(1) 054 .concatMap(value -> encode(value, bufferFactory, elementType, mimeType, hints)) 055 .doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release); 056 } 057 058 /** 059 * Encode {@code T} to an output {@link DataBuffer} stream. 060 * @param t the value to process 061 * @param dataBufferFactory a buffer factory used to create the output 062 * @param type the stream element type to process 063 * @param mimeType the mime type to process 064 * @param hints additional information about how to do decode, optional 065 * @return the output stream 066 */ 067 protected abstract Flux<DataBuffer> encode(T t, DataBufferFactory dataBufferFactory, 068 ResolvableType type, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints); 069 070}