KTLN-526 - Convert a Data Class to ByteBuffer in Kotlin

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

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

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

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

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

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

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

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

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

core-kotlin-modules/pom.xml

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