I’ll show you how to configure Gradle build for a Java/Scala project and integrate it with GitLab CI/CD so that it can be automatically released and published to a Maven repository.

The example uses Axion release Gradle plugin to manage version number using git tags and Maven Publish Gradle plugin to upload artifacts to a Maven (Nexus) repository.

As an extra step I’m demonstrating how to publish a distribution zip file to the Maven repository and then how to add a link to GitLab release. You can see distZip in the code below which is provided by the Distribution Gradle plugin.

Create new variables CI_REPOSITORY_USERNAME and CI_REPOSITORY_PASSWORD in your GitLab project (Settings > CI/CD > Variables). Set them to Maven repository authentication credentials. The user must have permissions to publish to the repository.

Interesting parts of ./build.gradle:

plugins {
 id 'application'
 id 'maven-publish'
 id 'pl.allegro.tech.build.axion-release' version '1.13.6'
}

ext {
 repository_username = System.env.CI_REPOSITORY_USERNAME
 repository_password = System.env.CI_REPOSITORY_PASSWORD
}

group = 'com.example'
version = scmVersion.version

publishing {
 repositories {
 maven {
 name 'nexus'
 // Enter your Maven repository URL here:
 def releasesRepoUrl = 'https://.../repositories/releases'
 def snapshotsRepoUrl = 'https://.../repositories/snapshots'
 url = version.endsWith('SNAPSHOT') ? snapshotsRepoUrl : releasesRepoUrl
 credentials {
 username repository_username
 password repository_password
 }
 }
 }
 publications {
 // This is an extra (optional) publication:
 mavenJava(MavenPublication) {
 from components.java
 artifact distZip
 }
 }
}

scmVersion {
 // Not really needed, but I like it:
 useHighestVersion = true
}

// Other parts which are not related to release & publish
...

Here’s the ./.gitlab-ci.yml file. Check GitLab documentation for more details:

default:
 image: openjdk:8

variables:
 GIT_STRATEGY: clone
 # Make sure that you get tags from git repository otherwise the release
 # Gradle plugin will not be able to create the next version number:
 GIT_FETCH_EXTRA_FLAGS: --tags 
 GRADLE_OPTS: "-Dorg.gradle.daemon=false"

before_script:
 - export GRADLE_USER_HOME=`pwd`/.gradle

stages:
 - build
 - deploy

build_job:
 stage: build
 script:
 - ./gradlew build

publish_job:
 stage: deploy
 rules:
 - if: $CI_COMMIT_TAG
 when: never
 - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
 script:
 - ./gradlew createRelease -Prelease.disableChecks
 - ./gradlew publish
 - echo "TAG=$(./gradlew currentVersion -q -Prelease.quiet)" >> variables.env
 artifacts:
 reports:
 dotenv: variables.env

release_job:
 stage: deploy
 image: registry.gitlab.com/gitlab-org/release-cli:latest
 needs:
 - job: publish_job
 artifacts: true
 rules:
 - if: $CI_COMMIT_TAG
 when: never
 - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
 script:
 - echo "Releasing $TAG"
 release:
 name: 'Release v$TAG'
 description: $CI_COMMIT_MESSAGE
 tag_name: v$TAG
 ref: $CI_COMMIT_SHA
 assets:
 links:
 - name: 'Installation zip'
 url: "https://...your Nexus.../service/local/artifact/maven/redirect?g=com.example&a=example-app&v=$TAG&r=releases&e=zip"