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Publish a Kotlin lib with gradle Kotlin DSL

· 4 min read

I wanted to play more with Kotlin and I wanted to publish KGeoGson lib to a remote maven repo.

I was following gradle guide to build my kotlin project with Kotlin DSL.

Bootstrap Kotlin project#

Create project directory with files of your library you want to build and publish. You may have a directory structure like the following:

project├── build.gradle.kts├── settings.gradle.kts└── my-kotlin-library    ├── build.gradle.kts    └── src        ├── main        │   └── kotlin        │       └── org        │           └── example        │               └── MyLibrary.kt        └── test            └── kotlin                └── org                    └── example                        └── MyLibraryTest.kt

Setup#

Root build.gradle.kts

plugins {   `build-scan`}
buildScan {   termsOfServiceUrl = "https://gradle.com/terms-of-service"   termsOfServiceAgree = "yes"
   publishAlways()}
val clean by tasks.creating(Delete::class) {   delete(rootProject.buildDir)}

In this file, « build-scan » plugin is activated and a clean task is added. That’s all for it

settings.gradle.kts

include("lib")

In this file, we define our modules

lib/build.gradle.kts

First we are adding some plugins

plugins {   // Add Kotlin plugin to build our Kotlin lib   kotlin("jvm") version "1.3.21"   // Get version from git tags   id("fr.coppernic.versioning") version "3.1.2"   // Documentation for our code   id("org.jetbrains.dokka") version "0.9.17"   // Publication to bintray   id("com.jfrog.bintray") version "1.8.4"   // Maven publication   `maven-publish`}

Then we are defining dependencies and their repositories for our code

repositories {   jcenter()   mavenCentral()}
dependencies {   implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk7")   implementation("com.google.code.gson:gson:2.8.5")
   testCompile("junit:junit:4.12")}

We need some more tasks to add sources and javadoc to our lib. We are starting by configuring dokka task:

tasks {   dokka {       outputFormat = "html"       outputDirectory = "$buildDir/javadoc"       moduleName = rootProject.name   }}

We can then bundle documentation into a jar

val dokkaJar by tasks.creating(Jar::class) {   group = JavaBasePlugin.DOCUMENTATION_GROUP   description = "Assembles Kotlin docs with Dokka"   archiveClassifier.set("javadoc")   from(tasks.dokka)   dependsOn(tasks.dokka)}

We are creating another jar containing sources

val sourcesJar by tasks.creating(Jar::class) {   archiveClassifier.set("sources")   from(sourceSets.getByName("main").allSource)}

At this stage, you are able to compile your lib. The most important part of this article begins. Let’s see how publication is working. It is very important to configure pom.xml file of maven artifact in a right manner. Otherwise you will not be able to submit your library into JCenter repo.

Let’s start configuring base of maven publish plugin

val artifactName = "libname"val artifactGroup = "org.example"
publishing {   publications {       create<MavenPublication>("lib") {           groupId = artifactGroup           artifactId = artifactName           // version is gotten from an external plugin           version = project.versioning.info.display           // This is the main artifact           from(components["java"])           // We are adding documentation artifact           artifact(dokkaJar)           // And sources           artifact(sourcesJar)       }   }}

Now we need to add information about package in pom.xml file. You can edit pom.xml with pom.withXml { code

val pomUrl = "..."val pomScmUrl = "..."val pomIssueUrl = "..."val pomDesc = "..."val pomScmConnection = ""..."val pomScmDevConnection = "..."
val githubRepo = "..."val githubReadme = "..."
val pomLicenseName = "The Apache Software License, Version 2.0"val pomLicenseUrl = "http://www.apache.org/licenses/LICENSE-2.0.txt"val pomLicenseDist = "repo"
val pomDeveloperId = "..."val pomDeveloperName = "..."

publishing {   publications {       create<MavenPublication>("lib") {           [...]
           pom.withXml {               asNode().apply {                   appendNode("description", pomDesc)                   appendNode("name", rootProject.name)                   appendNode("url", pomUrl)                   appendNode("licenses").appendNode("license").apply {                       appendNode("name", pomLicenseName)                       appendNode("url", pomLicenseUrl)                       appendNode("distribution", pomLicenseDist)                   }                   appendNode("developers").appendNode("developer").apply {                       appendNode("id", pomDeveloperId)                       appendNode("name", pomDeveloperName)                   }                   appendNode("scm").apply {                       appendNode("url", pomScmUrl)                       appendNode("connection", pomScmConnection)                   }               }           }       }   }}

Now that your maven publication is well configured, you can configure bintray plugin

bintray {   // Getting bintray user and key from properties file or command line   user = if (project.hasProperty("bintray_user")) project.property("bintray_user") as String else ""   key = if (project.hasProperty("bintray_key")) project.property("bintray_key") as String else ""
   // Automatic publication enabled   publish = true
   // Set maven publication onto bintray plugin   setPublications("lib")
   // Configure package   pkg.apply {       repo = "maven"       name = rootProject.name       setLicenses("Apache-2.0")       setLabels("Gson", "json", "GeoJson", "GPS", "Kotlin")       vcsUrl = pomScmUrl       websiteUrl = pomUrl       issueTrackerUrl = pomIssueUrl       githubRepo = githubRepo       githubReleaseNotesFile = githubReadme
       // Configure version       version.apply {           name = project.versioning.info.display           desc = pomDesc           released = Date().toString()           vcsTag = project.versioning.info.tag       }   }}

Here we is ! Happy publication !