Gradle Build Setup

Create a New Project

The fastest way is IntelliJ IDEA:

1. New Project → Kotlin → JVM Application
2. Set the project name and JDK (17+)
3. IntelliJ generates the Gradle files for you

Or create manually:

mkdir my-kotlin-app && cd my-kotlin-app
gradle init --type kotlin-application

Project Structure

my-kotlin-app/
├── build.gradle.kts          # Build configuration
├── settings.gradle.kts       # Project name and modules
├── gradle.properties         # Gradle + Kotlin version settings
├── src/
│   ├── main/kotlin/          # Source code
│   │   └── Main.kt
│   └── test/kotlin/          # Tests
│       └── MainTest.kt
└── gradle/
    └── wrapper/              # Gradle wrapper (don't edit)

build.gradle.kts — The Main Build File

plugins {
    kotlin("jvm") version "2.4.10"
    application
}

group = "com.example"
version = "1.0.0"

repositories {
    mavenCentral()
}

dependencies {
    // Kotlin standard library (added automatically by the kotlin plugin)

    // Coroutines
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.11.0")

    // Testing
    testImplementation(kotlin("test"))
}

// Application entry point
application {
    mainClass.set("com.example.MainKt")
}

settings.gradle.kts

pluginManagement {
    repositories {
        gradlePluginPortal()
        mavenCentral()
    }
}

rootProject.name = "my-kotlin-app"

Adding Dependencies

Use implementation for libraries your code needs at runtime:

dependencies {
    // JSON serialization
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.8.0")

    // Date and time
    implementation("org.jetbrains.kotlinx:kotlinx-datetime:0.6.2")

    // Testing
    testImplementation(kotlin("test"))
    testImplementation("io.mockk:mockk:1.13.16")
}

Dependency Keywords

Common Gradle Tasks

# Compile the project
./gradlew compileKotlin

# Run tests
./gradlew test

# Build a distributable (JAR or ZIP)
./gradlew installDist

# Run the application
./gradlew run

# Clean build outputs
./gradlew clean

# Build everything from scratch
./gradlew clean build

Multi-module Setup

For larger projects, split into modules. In settings.gradle.kts:

rootProject.name = "my-app"

include("core")
include("api")
include("cli")

Each module has its own build.gradle.kts. Modules can depend on each other:

// api/build.gradle.kts
dependencies {
    implementation(project(":core"))
}

Diagram: Multi-module Gradle project with core, api, and cli modules. api and cli both depend on core.

Loading diagram...

Gradle Wrapper

The gradlew (Unix) and gradlew.bat (Windows) scripts let you build without installing Gradle. They download the correct version automatically.

Always commit these files:

gradlew
gradlew.bat
gradle/wrapper/gradle-wrapper.properties
gradle/wrapper/gradle-wrapper.jar

To update the Gradle version:

./gradlew wrapper --gradle-version 8.14

Practice Exercise

Create a project with kotlinx.serialization and a data class:

1. Create a new Kotlin/JVM project in IntelliJ
2. Add the serialization plugin and dependency:

plugins {
    kotlin("jvm") version "2.4.10"
    kotlin("plugin.serialization") version "2.4.10"
    application
}

dependencies {
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.8.0")
}

3. Write the code:

import kotlinx.serialization.Serializable
import kotlinx.serialization.json.Json

@Serializable
data class Task(val id: Int, val title: String, val done: Boolean = false)

fun main() {
    val task = Task(1, "Learn Gradle")
    val json = Json.encodeToString(task)
    println(json)  // {"id":1,"title":"Learn Gradle","done":false}

    val decoded = Json.decodeFromString<Task>(json)
    println(decoded)  // Task(id=1, title=Learn Gradle, done=false)
}

4. Run with ./gradlew run