Introduce ServerCodecConfigurer
Issue: SPR-15247
This commit is contained in:
Rossen Stoyanchev
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/*
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* Copyright 2002-2017 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.http.codec;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.function.Supplier;
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import org.springframework.core.ResolvableType;
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import org.springframework.core.codec.ByteArrayDecoder;
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import org.springframework.core.codec.ByteArrayEncoder;
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import org.springframework.core.codec.ByteBufferDecoder;
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import org.springframework.core.codec.ByteBufferEncoder;
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import org.springframework.core.codec.CharSequenceEncoder;
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import org.springframework.core.codec.DataBufferDecoder;
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import org.springframework.core.codec.DataBufferEncoder;
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import org.springframework.core.codec.Decoder;
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import org.springframework.core.codec.Encoder;
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import org.springframework.core.codec.ResourceDecoder;
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import org.springframework.core.codec.StringDecoder;
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import org.springframework.http.codec.json.Jackson2JsonDecoder;
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import org.springframework.http.codec.json.Jackson2JsonEncoder;
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import org.springframework.http.codec.xml.Jaxb2XmlDecoder;
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import org.springframework.http.codec.xml.Jaxb2XmlEncoder;
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import org.springframework.util.ClassUtils;
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/**
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* Helps to configure a list of server-side HTTP message readers and writers
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* with support for built-in defaults and options to register additional custom
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* readers and writers via {@link #customCodec()}.
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*
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* <p>The built-in defaults include basic data types such as
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* {@link Byte byte[]}, {@link java.nio.ByteBuffer ByteBuffer},
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* {@link org.springframework.core.io.buffer.DataBuffer DataBuffer},
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* {@link String}, {@link org.springframework.core.io.Resource Resource},
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* in addition to JAXB2 and Jackson 2 based on classpath detection, as well as
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* support for Server-Sent Events. There are options to {@link #defaultCodec()
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* override} some of the defaults or to have them
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* {@link #registerDefaults(boolean) turned off} completely.
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*
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* @author Rossen Stoyanchev
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* @since 5.0
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*/
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public class ServerCodecConfigurer {
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private static final boolean jackson2Present =
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ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper",
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ServerCodecConfigurer.class.getClassLoader()) &&
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ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator",
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ServerCodecConfigurer.class.getClassLoader());
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private static final boolean jaxb2Present =
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ClassUtils.isPresent("javax.xml.bind.Binder", ServerCodecConfigurer.class.getClassLoader());
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private final DefaultCodecConfigurer defaultCodecs = new DefaultCodecConfigurer();
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private final CustomCodecConfigurer customCodecs = new CustomCodecConfigurer();
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/**
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* Provide overrides for built-in HTTP message readers and writers.
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*/
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public DefaultCodecConfigurer defaultCodec() {
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return this.defaultCodecs;
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}
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/**
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* Whether to make default HTTP message reader and writer registrations.
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* <p>By default this is set to {@code "true"}.
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*/
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public void registerDefaults(boolean register) {
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this.defaultCodec().setSuppressed(!register);
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}
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/**
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* Register a custom encoder or decoder.
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*/
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public CustomCodecConfigurer customCodec() {
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return this.customCodecs;
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}
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/**
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* Prepare a list of HTTP message readers.
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*/
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public List<ServerHttpMessageReader<?>> getReaders() {
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// Built-in, concrete Java type readers
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List<ServerHttpMessageReader<?>> result = new ArrayList<>();
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this.defaultCodecs.addReaderTo(result, ByteArrayDecoder.class, ByteArrayDecoder::new);
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this.defaultCodecs.addReaderTo(result, ByteBufferDecoder.class, ByteBufferDecoder::new);
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this.defaultCodecs.addReaderTo(result, DataBufferDecoder.class, DataBufferDecoder::new);
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this.defaultCodecs.addReaderTo(result, ResourceDecoder.class, ResourceDecoder::new);
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this.defaultCodecs.addStringReaderTextOnlyTo(result);
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// Custom, concrete Java type readers
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this.customCodecs.addTypedReadersTo(result);
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// Built-in, Object-based readers
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if (jaxb2Present) {
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this.defaultCodecs.addReaderTo(result, Jaxb2XmlDecoder.class, Jaxb2XmlDecoder::new);
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}
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if (jackson2Present) {
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this.defaultCodecs.addReaderTo(result, Jackson2JsonDecoder.class, Jackson2JsonDecoder::new);
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}
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// Custom, Object-based readers
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this.customCodecs.addObjectReadersTo(result);
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// Potentially overlapping Java types + "*/*"
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this.defaultCodecs.addStringReaderTo(result);
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return result;
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}
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/**
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* Prepare a list of HTTP message writers.
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*/
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public List<ServerHttpMessageWriter<?>> getWriters() {
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// Built-in, concrete Java type readers
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List<ServerHttpMessageWriter<?>> result = new ArrayList<>();
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this.defaultCodecs.addWriterTo(result, ByteArrayEncoder.class, ByteArrayEncoder::new);
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this.defaultCodecs.addWriterTo(result, ByteBufferEncoder.class, ByteBufferEncoder::new);
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this.defaultCodecs.addWriterTo(result, DataBufferEncoder.class, DataBufferEncoder::new);
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this.defaultCodecs.addWriterTo(result, ResourceHttpMessageWriter::new);
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this.defaultCodecs.addStringWriterTextPlainOnlyTo(result);
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// Custom, concrete Java type readers
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this.customCodecs.addTypedWritersTo(result);
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// Built-in, Object-based readers
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if (jaxb2Present) {
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this.defaultCodecs.addWriterTo(result, Jaxb2XmlEncoder.class, Jaxb2XmlEncoder::new);
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}
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if (jackson2Present) {
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this.defaultCodecs.addWriterTo(result, Jackson2JsonEncoder.class, Jackson2JsonEncoder::new);
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}
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this.defaultCodecs.addSseWriterTo(result);
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// Custom, Object-based readers
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this.customCodecs.addObjectWritersTo(result);
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// Potentially overlapping Java types + "*/*"
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this.defaultCodecs.addStringWriterTo(result);
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return result;
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}
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/**
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* A registry and a factory for built-in HTTP message readers and writers.
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*/
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public static class DefaultCodecConfigurer {
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private boolean suppressed = false;
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private final Map<Class<?>, ServerHttpMessageReader<?>> readers = new HashMap<>();
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private final Map<Class<?>, ServerHttpMessageWriter<?>> writers = new HashMap<>();
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/**
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* Override the default Jackson {@code Decoder}.
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* @param decoder the decoder to use
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*/
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public void jackson2Decoder(Jackson2JsonDecoder decoder) {
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this.readers.put(Jackson2JsonDecoder.class, new DecoderHttpMessageReader<>(decoder));
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}
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/**
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* Override the default Jackson {@code Encoder} for JSON. Also used for
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* SSE unless further overridden via {@link #sse(Encoder)}.
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* @param encoder the encoder to use
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*/
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public void jackson2Encoder(Jackson2JsonEncoder encoder) {
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this.writers.put(Jackson2JsonEncoder.class, new EncoderHttpMessageWriter<>(encoder));
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}
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/**
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* Configure the {@code Encoder} to use for Server-Sent Events.
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* <p>By default the {@link #jackson2Encoder} override is used for SSE.
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* @param encoder the encoder to use
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*/
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public void sse(Encoder<?> encoder) {
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ServerHttpMessageWriter<?> writer = new ServerSentEventHttpMessageWriter(encoder);
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this.writers.put(ServerSentEventHttpMessageWriter.class, writer);
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}
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// Internal methods for building a list of default readers or writers...
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private void setSuppressed(boolean suppressed) {
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this.suppressed = suppressed;
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}
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private <T, D extends Decoder<T>> void addReaderTo(List<ServerHttpMessageReader<?>> result,
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Class<D> key, Supplier<D> fallback) {
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addReaderTo(result, () -> findReader(key, fallback));
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}
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private void addReaderTo(List<ServerHttpMessageReader<?>> result,
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Supplier<ServerHttpMessageReader<?>> reader) {
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if (!this.suppressed) {
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result.add(reader.get());
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}
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}
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private <T, D extends Decoder<T>> DecoderHttpMessageReader<?> findReader(
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Class<D> key, Supplier<D> fallback) {
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DecoderHttpMessageReader<?> reader = (DecoderHttpMessageReader<?>) this.readers.get(key);
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return reader != null ? reader : new DecoderHttpMessageReader<>(fallback.get());
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}
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private <T, E extends Encoder<T>> void addWriterTo(List<ServerHttpMessageWriter<?>> result,
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Class<E> key, Supplier<E> fallback) {
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addWriterTo(result, () -> findWriter(key, fallback));
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}
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private void addWriterTo(List<ServerHttpMessageWriter<?>> result,
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Supplier<ServerHttpMessageWriter<?>> writer) {
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if (!this.suppressed) {
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result.add(writer.get());
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}
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}
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private <T, E extends Encoder<T>> EncoderHttpMessageWriter<?> findWriter(
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Class<E> key, Supplier<E> fallback) {
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EncoderHttpMessageWriter<?> writer = (EncoderHttpMessageWriter<?>) this.writers.get(key);
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return writer != null ? writer : new EncoderHttpMessageWriter<>(fallback.get());
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}
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private void addStringReaderTextOnlyTo(List<ServerHttpMessageReader<?>> result) {
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addReaderTo(result, () -> new DecoderHttpMessageReader<>(StringDecoder.textPlainOnly(true)));
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}
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private void addStringReaderTo(List<ServerHttpMessageReader<?>> result) {
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addReaderTo(result, () -> new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes(true)));
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}
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private void addStringWriterTextPlainOnlyTo(List<ServerHttpMessageWriter<?>> result) {
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addWriterTo(result, () -> new EncoderHttpMessageWriter<>(CharSequenceEncoder.textPlainOnly()));
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}
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private void addStringWriterTo(List<ServerHttpMessageWriter<?>> result) {
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addWriterTo(result, () -> new EncoderHttpMessageWriter<>(CharSequenceEncoder.allMimeTypes()));
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}
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private void addSseWriterTo(List<ServerHttpMessageWriter<?>> result) {
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addWriterTo(result, () -> {
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ServerHttpMessageWriter<?> writer = this.writers.get(ServerSentEventHttpMessageWriter.class);
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if (writer != null) {
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return writer;
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}
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if (jackson2Present) {
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return new ServerSentEventHttpMessageWriter(
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findWriter(Jackson2JsonEncoder.class, Jackson2JsonEncoder::new).getEncoder());
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}
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return new ServerSentEventHttpMessageWriter();
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});
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}
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}
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/**
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* Registry and container for custom HTTP message readers and writers.
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*/
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public static class CustomCodecConfigurer {
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private final List<ServerHttpMessageReader<?>> typedReaders = new ArrayList<>();
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private final List<ServerHttpMessageWriter<?>> typedWriters = new ArrayList<>();
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private final List<ServerHttpMessageReader<?>> objectReaders = new ArrayList<>();
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private final List<ServerHttpMessageWriter<?>> objectWriters = new ArrayList<>();
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/**
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* Add a custom {@code Decoder} internally wrapped with
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* {@link DecoderHttpMessageReader}).
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*/
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public void decoder(Decoder<?> decoder) {
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reader(new DecoderHttpMessageReader<>(decoder));
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}
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/**
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* Add a custom {@code Encoder}, internally wrapped with
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* {@link EncoderHttpMessageWriter}.
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*/
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public void encoder(Encoder<?> encoder) {
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writer(new EncoderHttpMessageWriter<>(encoder));
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}
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/**
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* Add a custom {@link ServerHttpMessageReader}. For readers of type
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* {@link DecoderHttpMessageReader} consider using the shortcut
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* {@link #decoder(Decoder)} instead.
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*/
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public void reader(ServerHttpMessageReader<?> reader) {
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boolean canReadToObject = reader.canRead(ResolvableType.forClass(Object.class), null);
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(canReadToObject ? this.objectReaders : this.typedReaders).add(reader);
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}
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/**
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* Add a custom {@link ServerHttpMessageWriter}. For readers of type
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* {@link EncoderHttpMessageWriter} consider using the shortcut
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* {@link #encoder(Encoder)} instead.
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*/
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public void writer(ServerHttpMessageWriter<?> writer) {
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boolean canWriteObject = writer.canWrite(ResolvableType.forClass(Object.class), null);
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(canWriteObject ? this.objectWriters : this.typedWriters).add(writer);
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}
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// Internal methods for building a list of custom readers or writers...
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private void addTypedReadersTo(List<ServerHttpMessageReader<?>> result) {
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result.addAll(this.typedReaders);
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}
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private void addObjectReadersTo(List<ServerHttpMessageReader<?>> result) {
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result.addAll(this.objectReaders);
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}
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private void addTypedWritersTo(List<ServerHttpMessageWriter<?>> result) {
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result.addAll(this.typedWriters);
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}
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private void addObjectWritersTo(List<ServerHttpMessageWriter<?>> result) {
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result.addAll(this.objectWriters);
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}
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}
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}
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