<spring initializer> creates the following build.g...

# spring

[Pihentagy]

spring initializer creates the following build.gradle.kts:

plugins {
  id("org.springframework.boot") version "3.3.0"
  id("io.spring.dependency-management") version "1.1.5"
  kotlin("jvm") version "1.9.24"
  kotlin("plugin.spring") version "1.9.24"
}
...

The kotlin("jvm") value is the kotlin version? Should it be equal to plugin.spring version? I do not know much about build.gradle(.kts), is there a basic article about the basics?

Can I upgrade and use kotlin 2.0?

[Robert Jaros]

It's good to also add:

extra["kotlin.version"] = "2.0.0"

[Pihentagy]

Cannot I specify in one place my desired kotlin version?

[Robert Jaros]

You can, but you need to use different project layout (e.g. using version catalog https://medium.com/@callmeryan/gradle-version-catalog-728111fa210f)

[thanksforallthefish]

how we do is in gradle.properties

kotlin_version=2.0.0
# Spring Boot overrides
kotlin.version=${kotlin_version}

and in build.gradle (but should work similarly for kts file)

plugins {
  id "org.jetbrains.kotlin.jvm" version "$kotlin_version"
  //etc
}

[Klitos Kyriacou]

By the way, kotlin(module: String) is just a convenience function that returns id("org.jetbrains.kotlin.$module"). That's good to know when you look at various example build.gradle.kts files and wonder why some use the kotlin function and others don't.

[Klitos Kyriacou]

> is there a basic article about the basics?
I hope someone can supply a useful link, but from my experience there's nothing "basic" about Gradle: the gradle.org website has a lot of documentation but when you look at the build file of a fully grown Gradle project and try to understand it, you'll find that you'll need to read almost all of the extensive documentation, and then you'll learn that various features quickly get deprecated with new versions, and that there are dozens of different (and incompatible) ways of doing the same thing.

[Pihentagy]

# Spring Boot overrides

Could you tell me about that override, @thanksforallthefish ?

[thanksforallthefish]

spring boot dependencies are managed by the dependency management plugin, but you can override those dependencies in your config files.

https://docs.spring.io/spring-boot/appendix/dependency-versions/coordinates.html presents the list of managed dependencies and their versions,

https://docs.spring.io/spring-boot/appendix/dependency-versions/properties.html presents the property you can define to override the default version, either in gradle.propertie or in extra (as Robert was pointing out). I think there are also other ways to define those properties, but honestly 2 is already one-too-many for my taste

[Pihentagy]

So, having a gradle.properties in project root with content

kotlin_version=2.0.0
# Spring Boot overrides
kotlin.version=${kotlin_version}

and after that, in build.gradle.kts

kotlin("jvm") version "$kotlin_version"
kotlin("plugin.spring") version "$kotlin_version"

// allows all Kotlin classes in a project to be open for subclassing by default.
kotlin("plugin.allopen") version "$kotlin_version"
kotlin("plugin.jpa") version "$kotlin_version"

I get

* What went wrong:
Script compilation errors:

  Line 12:     kotlin("jvm") version "$kotlin_version"
                                       ^ Unresolved reference: kotlin_version

  Line 13:     kotlin("plugin.spring") version "$kotlin_version"
                                                 ^ Unresolved reference: kotlin_version

  Line 16:     kotlin("plugin.allopen") version "$kotlin_version"
                                                  ^ Unresolved reference: kotlin_version

  Line 17:     kotlin("plugin.jpa") version "$kotlin_version"
                                              ^ Unresolved reference: kotlin_version

[Klitos Kyriacou]

This is happening because what you've defined as kotlin_version and kotlin.version are project properties, but the Kotlin DSL in your build file expects kotlin_version to be a Kotlin String variable. You can put this:

val kotlin_version: String by project

at the top of your build.gradle.kts file.

[Klitos Kyriacou]

By the way, you don't need the allopen plugin if you already have the spring plugin. Also, the plugins need to go in the plugins section, not the dependencies section where your kotlin("jvm") is.

[Pihentagy]

So:
gradle.properties

kotlin_version=2.0.0
# Spring Boot overrides
kotlin.version=${kotlin_version}
extra["kotlin_version"]="2.0.0"

build.gradle.kts

import java.util.*

val kotlin_version: String by project

group = "xxxxxx"
version = Properties().apply { load(file("build.properties").inputStream()) }.getProperty("VERSION")

plugins {
    id("org.springframework.boot") version "3.0.4"
    id("io.spring.dependency-management") version "1.1.0"
    id("jacoco")
    id("org.sonarqube") version "3.3"
    kotlin("jvm") version kotlin_version
    kotlin("plugin.spring") version kotlin_version
    kotlin("plugin.jpa") version kotlin_version

but still getting the same error.

[Pihentagy]

IDE hint: 'val kotlin_version: String' can't be called in this context by implicit receiver. Use the explicit one if necessary

[Klitos Kyriacou]

Ah, I just realised I misled you a bit. You can use the val kotlin_version inside your dependencies block (which is where you should define kotlin("jvm"), not in your plugins block). However, the plugins block unfortunately has restrictions which means you can't use this val inside the plugins block.

[thanksforallthefish]

tbh I don't know if it is a difference between groovy GString and kotlin string, but in groovy-gradle you can do

plugins {
  id "org.jetbrains.kotlin.jvm" version "$kotlin_version"
}

however you cannot do

plugins {
  id "org.jetbrains.kotlin.jvm" version kotlin_version
}

note: kotlin_version defined in gradle.properties. it's true the docs say Where «plugin id» and «plugin version» must be constant, literal strings. though

personally I haven't made the switch to kotlin-gradle yet, last time I tried it was too slow, though I think it was at least a couple of years ago and in the meantime a lot of improvements happened

[thanksforallthefish]

it seems kotlin needs an extra step in settings file: https://github.com/gradle/gradle/issues/1697#issuecomment-655682357

//gradle.properties
kotlinVersion=2.0.0
kotlin.version=${kotlin_version}

// settings.gradle.kts:
pluginManagement {
    val kotlinVersion: String by extra
    plugins {
        id("org.jetbrains.kotlin.jvm").version(kotlinVersion)
    }
}

//build.gradle.kts
plugins {
    // Apply plugins without versions:
    id("org.jetbrains.kotlin.jvm")
}

[Klitos Kyriacou]

I told you Gradle was complicated, didn't I? 😉

[Pihentagy]

I hoped in the past, that kotlin dsl is a bit simpler, but seem it has so many dependencies, that I continue to avoid any contact with gradle 😢

[thanksforallthefish]

I like gradle more than maven by a mile, but it's true that it's complicated, and the 2 dsl, and the freedom coming from the possibility of doing things in multiple ways (and I think declarative gradle was announced recently, https://declarative.gradle.org/docs/getting-started/) don't make for an easy experience