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Add kotlinx.serialization JSON support to Spring Messaging
Closes gh-25883
1 parent f329748 commit 3f01af6

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‎spring-messaging/spring-messaging.gradle

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description = "Spring Messaging"
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apply plugin: "kotlin"
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apply plugin: "kotlinx-serialization"
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dependencies {
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compile(project(":spring-beans"))
@@ -17,6 +18,7 @@ dependencies {
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optional("javax.xml.bind:jaxb-api")
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optional("com.google.protobuf:protobuf-java-util")
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optional("org.jetbrains.kotlinx:kotlinx-coroutines-reactor")
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optional("org.jetbrains.kotlinx:kotlinx-serialization-json")
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testCompile(project(":kotlin-coroutines"))
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testCompile(testFixtures(project(":spring-core")))
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testCompile("javax.inject:javax.inject-tck")

‎spring-messaging/src/main/java/org/springframework/messaging/converter/KotlinSerializationJsonMessageConverter.java

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/*
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* Copyright 2002-2020 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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* https://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.messaging.converter;
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import java.io.IOException;
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import java.io.Reader;
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import java.io.Writer;
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import java.lang.reflect.Type;
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import java.util.Map;
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import kotlinx.serialization.KSerializer;
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import kotlinx.serialization.SerializersKt;
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import kotlinx.serialization.json.Json;
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import org.springframework.util.ConcurrentReferenceHashMap;
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import org.springframework.util.FileCopyUtils;
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/**
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* Implementation of {@link MessageConverter} that can read and write JSON
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* using <a href="https://github.com/Kotlin/kotlinx.serialization">kotlinx.serialization</a>.
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*
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* <p>This converter can be used to bind {@code @Serializable} Kotlin classes.
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*
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* @author Sebastien Deleuze
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* @since 5.3
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*/
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public class KotlinSerializationJsonMessageConverter extends AbstractJsonMessageConverter {
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private static final Map<Type, KSerializer<Object>> serializerCache = new ConcurrentReferenceHashMap<>();
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private final Json json;
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/**
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* Construct a new {@code KotlinSerializationJsonMessageConverter} with default configuration.
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*/
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public KotlinSerializationJsonMessageConverter() {
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this(Json.Default);
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}
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/**
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* Construct a new {@code KotlinSerializationJsonMessageConverter} with the given delegate.
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* @param json the Json instance to use
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*/
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public KotlinSerializationJsonMessageConverter(Json json) {
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this.json = json;
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}
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@Override
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protected Object fromJson(Reader reader, Type resolvedType) {
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try {
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return fromJson(FileCopyUtils.copyToString(reader), resolvedType);
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}
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catch (IOException ex) {
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throw new MessageConversionException("Could not read JSON: " + ex.getMessage(), ex);
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}
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}
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@Override
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protected Object fromJson(String payload, Type resolvedType) {
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return this.json.decodeFromString(serializer(resolvedType), payload);
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}
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@Override
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protected void toJson(Object payload, Type resolvedType, Writer writer) {
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try {
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writer.write(toJson(payload, resolvedType).toCharArray());
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}
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catch (IOException ex) {
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throw new MessageConversionException("Could not write JSON: " + ex.getMessage(), ex);
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}
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}
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@Override
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protected String toJson(Object payload, Type resolvedType) {
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return this.json.encodeToString(serializer(resolvedType), payload);
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}
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/**
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* Tries to find a serializer that can marshall or unmarshall instances of the given type
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* using kotlinx.serialization. If no serializer can be found, an exception is thrown.
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* <p>Resolved serializers are cached and cached results are returned on successive calls.
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* @param type the type to find a serializer for
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* @return a resolved serializer for the given type
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* @throws RuntimeException if no serializer supporting the given type can be found
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*/
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private KSerializer<Object> serializer(Type type) {
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KSerializer<Object> serializer = serializerCache.get(type);
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if (serializer == null) {
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serializer = SerializersKt.serializer(type);
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serializerCache.put(type, serializer);
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}
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return serializer;
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}
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}

‎spring-messaging/src/main/java/org/springframework/messaging/simp/config/AbstractMessageBrokerConfiguration.java

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@@ -36,6 +36,7 @@
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import org.springframework.messaging.converter.DefaultContentTypeResolver;
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import org.springframework.messaging.converter.GsonMessageConverter;
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import org.springframework.messaging.converter.JsonbMessageConverter;
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import org.springframework.messaging.converter.KotlinSerializationJsonMessageConverter;
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import org.springframework.messaging.converter.MappingJackson2MessageConverter;
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import org.springframework.messaging.converter.MessageConverter;
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import org.springframework.messaging.converter.StringMessageConverter;
@@ -101,13 +102,16 @@ public abstract class AbstractMessageBrokerConfiguration implements ApplicationC
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private static final boolean jsonbPresent;
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private static final boolean kotlinSerializationJsonPresent;
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static {
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ClassLoader classLoader = AbstractMessageBrokerConfiguration.class.getClassLoader();
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jackson2Present = ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", classLoader) &&
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ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator", classLoader);
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gsonPresent = ClassUtils.isPresent("com.google.gson.Gson", classLoader);
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jsonbPresent = ClassUtils.isPresent("javax.json.bind.Jsonb", classLoader);
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kotlinSerializationJsonPresent = ClassUtils.isPresent("kotlinx.serialization.json.Json", classLoader);
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}
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@@ -411,6 +415,9 @@ else if (gsonPresent) {
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else if (jsonbPresent) {
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converters.add(new JsonbMessageConverter());
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}
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else if (kotlinSerializationJsonPresent) {
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converters.add(new KotlinSerializationJsonMessageConverter());
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}
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}
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return new CompositeMessageConverter(converters);
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}

‎spring-messaging/src/test/kotlin/org/springframework/messaging/converter/KotlinSerializationJsonMessageConverterTests.kt

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/*
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* Copyright 2002-2019 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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* https://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.messaging.converter
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import kotlinx.serialization.Serializable
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import org.assertj.core.api.Assertions
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import org.junit.jupiter.api.Test
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import org.springframework.core.MethodParameter
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import org.springframework.messaging.support.MessageBuilder
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import java.nio.charset.StandardCharsets
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import kotlin.reflect.typeOf
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@Suppress("UsePropertyAccessSyntax")
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class KotlinSerializationJsonMessageConverterTests {
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private val converter = KotlinSerializationJsonMessageConverter()
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@Test
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fun readObject() {
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val payload = """
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{
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"bytes": [
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1,
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2
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],
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"array": [
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"Foo",
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"Bar"
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],
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"number": 42,
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"string": "Foo",
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"bool": true,
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"fraction": 42
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}
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""".trimIndent()
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val message = MessageBuilder.withPayload(payload.toByteArray(StandardCharsets.UTF_8)).build()
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val result = converter.fromMessage(message, SerializableBean::class.java) as SerializableBean
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Assertions.assertThat(result.bytes).containsExactly(0x1, 0x2)
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Assertions.assertThat(result.array).containsExactly("Foo", "Bar")
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Assertions.assertThat(result.number).isEqualTo(42)
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Assertions.assertThat(result.string).isEqualTo("Foo")
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Assertions.assertThat(result.bool).isTrue()
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Assertions.assertThat(result.fraction).isEqualTo(42.0f)
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}
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@Test
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@Suppress("UNCHECKED_CAST")
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fun readArrayOfObjects() {
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val payload = """
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[
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{
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"bytes": [
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1,
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2
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],
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"array": [
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"Foo",
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"Bar"
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],
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"number": 42,
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"string": "Foo",
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"bool": true,
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"fraction": 42
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}
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]
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""".trimIndent()
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val message = MessageBuilder.withPayload(payload.toByteArray(StandardCharsets.UTF_8)).build()
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val result = converter.fromMessage(message, Array<SerializableBean>::class.java) as Array<SerializableBean>
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Assertions.assertThat(result).hasSize(1)
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Assertions.assertThat(result[0].bytes).containsExactly(0x1, 0x2)
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Assertions.assertThat(result[0].array).containsExactly("Foo", "Bar")
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Assertions.assertThat(result[0].number).isEqualTo(42)
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Assertions.assertThat(result[0].string).isEqualTo("Foo")
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Assertions.assertThat(result[0].bool).isTrue()
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Assertions.assertThat(result[0].fraction).isEqualTo(42.0f)
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}
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@Test
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@Suppress("UNCHECKED_CAST")
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@ExperimentalStdlibApi
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fun readGenericCollection() {
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val payload = """
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[
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{
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"bytes": [
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1,
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2
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],
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"array": [
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"Foo",
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"Bar"
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],
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"number": 42,
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"string": "Foo",
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"bool": true,
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"fraction": 42
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}
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]
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""".trimIndent()
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val method = javaClass.getDeclaredMethod("handleList", List::class.java)
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val param = MethodParameter(method, 0)
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val message = MessageBuilder.withPayload(payload.toByteArray(StandardCharsets.UTF_8)).build()
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val result = converter.fromMessage(message, typeOf<List<SerializableBean>>()::class.java, param) as List<SerializableBean>
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Assertions.assertThat(result).hasSize(1)
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Assertions.assertThat(result[0].bytes).containsExactly(0x1, 0x2)
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Assertions.assertThat(result[0].array).containsExactly("Foo", "Bar")
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Assertions.assertThat(result[0].number).isEqualTo(42)
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Assertions.assertThat(result[0].string).isEqualTo("Foo")
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Assertions.assertThat(result[0].bool).isTrue()
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Assertions.assertThat(result[0].fraction).isEqualTo(42.0f)
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}
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@Test
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fun readFailsOnInvalidJson() {
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val payload = """
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this is an invalid JSON document
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""".trimIndent()
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val message = MessageBuilder.withPayload(payload.toByteArray(StandardCharsets.UTF_8)).build()
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Assertions.assertThatExceptionOfType(MessageConversionException::class.java).isThrownBy {
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converter.fromMessage(message, SerializableBean::class.java)
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}
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}
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@Test
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fun writeObject() {
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val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, "Foo", true, 42.0f)
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val message = converter.toMessage(serializableBean, null)
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val result = String((message!!.payload as ByteArray), StandardCharsets.UTF_8)
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Assertions.assertThat(result)
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.contains("\"bytes\":[1,2]")
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.contains("\"array\":[\"Foo\",\"Bar\"]")
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.contains("\"number\":42")
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.contains("\"string\":\"Foo\"")
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.contains("\"bool\":true")
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.contains("\"fraction\":42.0")
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}
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@Test
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fun writeObjectWithNullableProperty() {
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val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, null, true, 42.0f)
160+
val message = converter.toMessage(serializableBean, null)
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val result = String((message!!.payload as ByteArray), StandardCharsets.UTF_8)
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Assertions.assertThat(result)
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.contains("\"bytes\":[1,2]")
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.contains("\"array\":[\"Foo\",\"Bar\"]")
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.contains("\"number\":42")
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.contains("\"string\":null")
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.contains("\"bool\":true")
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.contains("\"fraction\":42.0")
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}
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@Test
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fun writeArrayOfObjects() {
174+
val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, "Foo", true, 42.0f)
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val expectedJson = """
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[{"bytes":[1,2],"array":["Foo","Bar"],"number":42,"string":"Foo","bool":true,"fraction":42.0}]
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""".trimIndent()
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val message = converter.toMessage(arrayOf(serializableBean), null)
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val result = String((message!!.payload as ByteArray), StandardCharsets.UTF_8)
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Assertions.assertThat(result).isEqualTo(expectedJson)
183+
}
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@Test
186+
@ExperimentalStdlibApi
187+
fun writeGenericCollection() {
188+
val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, "Foo", true, 42.0f)
189+
val expectedJson = """
190+
[{"bytes":[1,2],"array":["Foo","Bar"],"number":42,"string":"Foo","bool":true,"fraction":42.0}]
191+
""".trimIndent()
192+
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val method = javaClass.getDeclaredMethod("handleList", List::class.java)
194+
val param = MethodParameter(method, 0)
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val message = converter.toMessage(arrayListOf(serializableBean), null, param)
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val result = String((message!!.payload as ByteArray), StandardCharsets.UTF_8)
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Assertions.assertThat(result).isEqualTo(expectedJson)
199+
}
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@Suppress("UNUSED_PARAMETER")
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fun handleList(payload: List<SerializableBean>) {}
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@Serializable
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@Suppress("ArrayInDataClass")
206+
data class SerializableBean(
207+
val bytes: ByteArray,
208+
val array: Array<String>,
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val number: Int,
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val string: String?,
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val bool: Boolean,
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val fraction: Float
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)
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}

‎src/docs/asciidoc/languages/kotlin.adoc

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=== Kotlin multiplatform serialization
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As of Spring Framework 5.3, https://github.com/Kotlin/kotlinx.serialization[Kotlin multiplatform serialization] is
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supported in Spring MVC and Spring WebFlux. The builtin support currently only targets JSON format.
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supported in Spring MVC, Spring WebFlux and Spring Messaging. The builtin support currently only targets JSON format.
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To enable it, follow https://github.com/Kotlin/kotlinx.serialization#setup[those instructions] and make sure neither
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Jackson, GSON or JSONB are in the classpath.

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