Gradle — практический старт — build.gradle.kts (минимум)

plugins {
    java
    application
}

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

repositories {
    mavenCentral()
}

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-web:3.2.5")
    testImplementation("org.springframework.boot:spring-boot-starter-test")
}

java {
    toolchain {
        languageVersion.set(JavaLanguageVersion.of(21))
    }
}

application {
    mainClass.set("com.example.App")
}

tasks.test {
    useJUnitPlatform()
}