Spring Boot

Kargo’s spring-boot framework sets up everything the Spring Boot Gradle plugin and Kotlin Spring plugins would.

Create the project

kargo new greeter -w spring-boot
cd greeter
kargo run

kargo.toml

[frameworks]
spring-boot = { starters = ["web"] }

The generated app has one REST endpoint:

src/Main.kt

package com.example.greeter

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RequestParam
import org.springframework.web.bind.annotation.RestController

@SpringBootApplication
class Application

@RestController
class GreetingController {
    @GetMapping("/")
    fun greet(
        @RequestParam(defaultValue = "World") name: String,
    ) = greeting(name)
}

fun greeting(name: String) = "Hello, $name!"

fun main(args: Array<String>) {
    runApplication<Application>(args = args)
}

$ curl 'localhost:8080/?name=Kargo'
Hello, Kargo!

Starters

Each entry in starters adds org.springframework.boot:spring-boot-starter-<name>. Versions come from the Spring Boot BOM, so you never write them:

[frameworks]
spring-boot = { version = "4.1.1", starters = ["web", "data-jpa", "validation", "actuator"] }

[dependencies]
"com.h2database:h2" = { scope = "runtime" }       # version managed by the Spring Boot BOM
"org.postgresql:postgresql" = { scope = "runtime" }

JPA entities

With data-jpa (or jpa = true), Kargo enables the noarg and allopen compiler plugins for @Entity, @MappedSuperclass and @Embeddable, so Kotlin classes work as JPA entities:

import jakarta.persistence.*
import org.springframework.data.jpa.repository.JpaRepository

@Entity
class Book(
    var title: String,
    var author: String,
    @Id @GeneratedValue var id: Long? = null,
)

interface BookRepository : JpaRepository<Book, Long> {
    fun findByAuthor(author: String): List<Book>
}

Configuration

resources/application.properties (or application.yml) is on the classpath:

resources/application.properties

server.port=8081
spring.jpa.hibernate.ddl-auto=update

Testing

spring-boot-starter-test is added to the tests automatically:

tests-jvm/ApplicationTest.kt

package com.example.greeter

import org.junit.jupiter.api.Test
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.context.SpringBootTest
import kotlin.test.assertEquals

@SpringBootTest
class ApplicationTest {
    @Autowired lateinit var controller: GreetingController

    @Test
    fun greets() {
        assertEquals("Hello, Spring!", controller.greet("Spring"))
    }
}

Packaging

kargo package --release
java -jar target/release/jvm/greeter-0.1.0-all.jar