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KTLN-526 - Convert a Data Class to ByteBuffer in Kotlin (#1090)
* feat: data class to and from byte buffer * fix: properties in xml, user class
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‎core-kotlin-modules/core-kotlin-11/README.md

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### Relevant Articles

‎core-kotlin-modules/core-kotlin-11/pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
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http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-kotlin-11</artifactId>
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<name>core-kotlin-11</name>
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<packaging>jar</packaging>
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<parent>
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<groupId>com.baeldung</groupId>
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<artifactId>core-kotlin-modules</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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</parent>
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<dependencies>
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<dependency>
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<groupId>org.jetbrains.kotlin</groupId>
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<artifactId>kotlin-maven-serialization</artifactId>
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<version>${kotlin.version}</version>
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</dependency>
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<dependency>
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<groupId>org.jetbrains.kotlinx</groupId>
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<artifactId>kotlinx-serialization-json</artifactId>
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<version>${kotlinx.serialization.version}</version>
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</dependency>
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<dependency>
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<groupId>com.esotericsoftware.kryo</groupId>
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<artifactId>kryo</artifactId>
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<version>${kryo.version}</version>
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</dependency>
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</dependencies>
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<build>
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<sourceDirectory>src/main/kotlin</sourceDirectory>
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<testSourceDirectory>src/test/kotlin</testSourceDirectory>
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<plugins>
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<plugin>
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<groupId>org.jetbrains.kotlin</groupId>
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<artifactId>kotlin-maven-plugin</artifactId>
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<version>${kotlin.version}</version>
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<executions>
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<execution>
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<id>compile</id>
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<phase>compile</phase>
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<goals>
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<goal>compile</goal>
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</goals>
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</execution>
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</executions>
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<configuration>
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<compilerPlugins>
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<plugin>kotlinx-serialization</plugin>
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</compilerPlugins>
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</configuration>
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</plugin>
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</plugins>
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</build>
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<properties>
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<kotlinx.serialization.version>1.4.1</kotlinx.serialization.version>
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<kryo.version>2.24.0</kryo.version>
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</properties>
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</project>

‎core-kotlin-modules/core-kotlin-11/src/main/kotlin/com/baeldung/dataclasstobytebuffer/User.kt

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package com.baeldung.dataclasstobytebuffer
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import com.esotericsoftware.kryo.Kryo
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import com.esotericsoftware.kryo.io.Input
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import com.esotericsoftware.kryo.io.Output
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import java.io.ByteArrayInputStream
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import java.io.ByteArrayOutputStream
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import java.nio.ByteBuffer
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data class User(val id: Int = 0, val name: String = "", val age: Int = 0)
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fun User.manualToByteBuffer(): ByteBuffer {
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val nameBytes = this.name.toByteArray(Charsets.UTF_8)
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val buffer = ByteBuffer.allocate(Int.SIZE_BYTES + nameBytes.size + Int.SIZE_BYTES)
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buffer.putInt(this.id)
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buffer.put(nameBytes)
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buffer.putInt(this.age)
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buffer.flip() // Prepare the buffer for reading
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return buffer
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}
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fun ByteBuffer.manualToUser(): User {
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val id = this.int
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val nameBytes = ByteArray(this.remaining() - Int.SIZE_BYTES)
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this.get(nameBytes)
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val name = String(nameBytes, Charsets.UTF_8)
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val age = this.int
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return User(id, name, age)
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}
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// Using Kryo
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fun User.toByteBufferWithKryo(kryo: Kryo): ByteBuffer {
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val byteArrayOutputStream = ByteArrayOutputStream()
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val output = Output(byteArrayOutputStream)
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kryo.writeObject(output, this)
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output.close()
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val byteArray = byteArrayOutputStream.toByteArray()
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return ByteBuffer.wrap(byteArray)
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}
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fun ByteBuffer.toUserWithKryo(kryo: Kryo): User {
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val byteArray = ByteArray(this.remaining())
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this.get(byteArray)
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val byteArrayInputStream = ByteArrayInputStream(byteArray)
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val input = Input(byteArrayInputStream)
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return kryo.readObject(input, User::class.java).also { input.close() }
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}

‎core-kotlin-modules/core-kotlin-11/src/main/kotlin/com/baeldung/dataclasstobytebuffer/UserInputOutputStream.kt

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package com.baeldung.dataclasstobytebuffer
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import java.io.*
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import java.nio.ByteBuffer
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data class UserInputOutputStream(val id: Int, val name: String, val age: Int) : Serializable
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fun UserInputOutputStream.outputStreamByteBuffer(): ByteBuffer {
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val byteArrayOutputStream = ByteArrayOutputStream()
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val objectOutputStream = ObjectOutputStream(byteArrayOutputStream)
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objectOutputStream.writeObject(this)
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objectOutputStream.flush()
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val byteArray = byteArrayOutputStream.toByteArray()
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return ByteBuffer.wrap(byteArray)
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}
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fun ByteBuffer.inputStreamToUser(): UserInputOutputStream {
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val byteArray = ByteArray(this.remaining())
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this.get(byteArray)
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val byteArrayInputStream = ByteArrayInputStream(byteArray)
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val objectInputStream = ObjectInputStream(byteArrayInputStream)
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return objectInputStream.readObject() as UserInputOutputStream
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}

‎core-kotlin-modules/core-kotlin-11/src/main/kotlin/com/baeldung/dataclasstobytebuffer/UserSerialization.kt

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package com.baeldung.dataclasstobytebuffer
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import kotlinx.serialization.Serializable
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import kotlinx.serialization.decodeFromString
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import kotlinx.serialization.encodeToString
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import kotlinx.serialization.json.Json
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import java.nio.ByteBuffer
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import java.nio.charset.StandardCharsets
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@Serializable
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data class UserSerialization(val id: Int, val name: String, val age: Int)
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fun UserSerialization.userToJson(): ByteBuffer {
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val jsonString = Json.encodeToString(this)
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val byteArray = jsonString.toByteArray()
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return ByteBuffer.wrap(byteArray)
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}
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fun ByteBuffer.jsonToUser(): UserSerialization {
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val byteArray = ByteArray(this.remaining())
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this.get(byteArray)
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val jsonString = String(byteArray, StandardCharsets.UTF_8)
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return Json.decodeFromString(jsonString)
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}

‎core-kotlin-modules/core-kotlin-11/src/test/kotlin/com/baeldung/dataclasstobytebuffer/DataClassToByteBufferUnitTest.kt

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package com.baeldung.dataclasstobytebuffer
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import com.esotericsoftware.kryo.Kryo
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import org.junit.Test
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import org.junit.jupiter.api.Assertions.assertEquals
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class DataClassToByteBufferUnitTest {
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private val kryo = Kryo().apply {
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register(User::class.java)
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}
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@Test
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fun `Manual serialize and deserialize with fixed size`() {
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val user = User(id = 1, name = "Alice", age = 30)
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val serializedUser = user.manualToByteBuffer()
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val deserializedUser = serializedUser.manualToUser()
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assertEquals(user, deserializedUser)
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}
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@Test
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fun `Serialize and deserialize using byte array output and input stream`() {
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val user = UserInputOutputStream(id = 1, name = "Alice", age = 30)
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val serializedUser = user.outputStreamByteBuffer()
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val deserializedUser = serializedUser.inputStreamToUser()
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assertEquals(user, deserializedUser)
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}
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@Test
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fun `Serialize and deserialize using kotlin serialization library`() {
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val user = UserSerialization(id = 1, name = "Alice", age = 30)
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val serializedUser = user.userToJson()
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val deserializedUser = serializedUser.jsonToUser()
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assertEquals(user, deserializedUser)
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}
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@Test
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fun `Serialize and deserialize using Kryo library`() {
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val user = User(id = 1, name = "Alice", age = 30)
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val serializedUser = user.toByteBufferWithKryo(kryo)
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val deserializedUser = serializedUser.toUserWithKryo(kryo)
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assertEquals(user, deserializedUser)
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}
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}

‎core-kotlin-modules/pom.xml

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<module>core-kotlin-8</module>
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<module>core-kotlin-9</module>
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<module>core-kotlin-10</module>
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<module>core-kotlin-11</module>
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<module>core-kotlin-advanced</module>
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<module>core-kotlin-advanced-2</module>
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<module>core-kotlin-advanced-3</module>

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