Intro

Publishing to Maven Central for first time can be a challenging task, especially using Gradle. I prepared this tutorial shortly after successful publication of my second library; this tutorial assumes you already have an account at Jira, so I'll be focusing on the actual publishing steps.

Process

I searched and skimmed over several tutorials and examples on publishing with Gradle, but they differ and some are outdated, so in the end I spent almost a day figuring it out.

First of all you will need to create or reuse GPG keys. I've done this on Linux, and I had to install 'gnupg2' key tool first. Other tutorials cover the creation and upload of keys sufficiently, so I will tell you what you need to do with the keys in Gradle context. You need to export your generated key to a file using this command:

gpg2 --export-secret-keys AABBCCDD > AABBCCDD.gpg 

After that create a file 'gradle.properties' in the '.gradle' directory. This file is where your confidential info will go into.

Now let's look at a sample gradle script:

plugins {
    id 'java-library'
    // these 4 plugins are necessary
    id("io.github.gradle-nexus.publish-plugin") version "1.1.0"
    id 'maven-publish'
    id 'maven'
    id 'signing'
}

group ='your.group'
archivesBaseName = 'archive name'
version("0.1.0")

sourceCompatibility=JavaVersion.VERSION_11
targetCompatibility=JavaVersion.VERSION_11

repositories {
    mavenCentral()
}

dependencies {
    //your dependencies
}

task('sourceJar', type: Jar){
    classifier('sources')
    from sourceSets.main.allSource
}

task javadocJar(type: Jar) {
    classifier('javadoc')
    from javadoc
}

dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.12'
}

publishing {
    publications{
        javaPubl(MavenPublication){
            from components.java
            artifact sourceJar
            artifact javadocJar
            artifactId 'your-artifact-id'
            //POM configuration
            pom {
                name= "First name Last name"
                description="..."
                url = "project URL"
                licenses{
                    license{
                        name ="name of the license"
                        url="...and its URL"
                    }
                }
                developers{
                    developer{
                        name="First name Last Name"
                        email="your email"
                    }
                }
                //"Source Control Management"
                scm{
                    //'git' for Git, 'svn' for Subversion, and so on...
                    connection ="scm:git:[http link to repository]"
                    developerConnection ="scm:git:[https link to the repository]"
                    url= "arbitrary link to the repository"
                }
            }
        }
    }
}

signing {
    // 'javaPubl' is the name of the publication above
    sign publishing.publications.javaPubl
}


nexusPublishing {
    repositories {
        sonatype{
            //assigning from the 'gradle.properties' files
            username=project.property("user")
            password=project.property("password")
        }
    }
}

uploadArchives {
    repositories {
        mavenDeployer {
            //assigning from the file as well
            repository(
                    url: "${nexusUrl}/content/repositories/releases") {
                authentication(userName: "$user", password: "$password")
            }
            snapshotRepository(
                    url: "${nexusUrl}/content/repositories/snapshots") {
                authentication(userName: "$user", password: "$password")
            }
        }
    }
}
 

This is a minimal required script. The properties 'user', 'password', 'nexusUrl' are stored in 'gradle.properties', as well as signing details like so:

        user=your Sonatype username
        password=your Sonatype password

        signing.keyId=AABBCCDD (last 8 digits)
        signing.password=key passphrase
        signing.secretKeyRingFile=/location/of/the/key/file.gpg
        nexusUrl=https://oss.sonatype.org (as of 2021)
        

When the properties are filled out, and your project is ready, you must execute command

./gradlew publishToSonatype closeAndReleaseSonatypeStagingRepository
 

If the deployment fails, you can view why at the Nexus Repository Manager. Otherwise, deployment will end with success.