Publishing Android library to maven central

All my libraries has a script to publish the artifact to bintray and from there auto release to mavenCentral. But recently, Bintray was shutdown and hence I have to publish directly to maven central repository. This is how I did it.

Requirements

1. You need to have access to Sonatype OSSRH, i.e, you should be able to login to https://oss.sonatype.org. If you don’t, register for an account. This involves you creating a JIRA ticket for a new project.
2. Username (OSS_USERNAME) and Password (OSS_PASSWORD) used to log in to Sonatype account.
3. StagingProfileId (OSS_STAGING_PROFILE_ID). You get this by clicking on Staging Profiles on the left pane of your Sonatype Account, and then selecting a profile in the right pane. Check the url in the address bar. It should appear something like https://oss.sonatype.org/#stagingProfiles;721f909fe89978. So 721f909fe89978 is your StagingProfileId.
4. PGP Key, specifically, keyId, key and password. If you are not sure how to generate PGP key pair, refer this. If you have already generated the key pair, then execute gpg --list-keys to get a list of keys in your system. Choose the one you are going to sign your artifacts.
   
   keyId(OSS_SIGNING_KEY_ID) - this would be something like CA925CD6C9E8D064FF05B4728190C4130ABA0F98. Either use the full string or the last 8 digits 0ABA0F98.
   key(OSS_SIGNING_KEY) - get this by executing gpg --export-secret-keys 0ABA0F98 | base64. password(OSS_SIGNING_PASSWORD) - this is the passphrase that you used when generating your key pair

Project level Gradle script

• Add the gradle-nexus-publish-plugin to your build.gradle script at the root level.

  plugins {
    id("io.github.gradle-nexus.publish-plugin").version("1.1.0")
  }
  

• Add the publishing configuration to access your Sonatype account. Refer documentation if you have registered your Sonatype account after 24 Feb 2021.

  // Publish to Maven Central
  nexusPublishing {
    repositories {
        sonatype {
            username = System.getenv("OSS_USERNAME")
            password = System.getenv("OSS_PASSWORD")
            stagingProfileId = System.getenv("OSS_STAGING_PROFILE_ID")
        }
    }
  }
  

Module level Gradle script

• Add the below publish.gradle script to your Module.

apply plugin: 'maven-publish'
apply plugin: 'signing'

// If you want to publish your sources as well
task androidSourcesJar(type: Jar) {
    archiveClassifier.set('sources')
    from android.sourceSets.main.java.srcDirs
    from android.sourceSets.main.kotlin.srcDirs
}

artifacts {
    archives androidSourcesJar
}

group = GROUP_ID
version = VERSION

afterEvaluate {
    publishing {
        publications {
            release(MavenPublication) {

                groupId GROUP_ID
                artifactId ARTIFACT_ID
                version VERSION

                from components.release
                artifact androidSourcesJar

                pom {
                    name = ARTIFACT_ID
                    description = 'An android library that ...'
                    url = SITE_URL
                    licenses {
                        // Your licensing information
                        license {
                            name = 'The Apache Software License, Version 2.0'
                            url = 'http://www.apache.org/licenses/LICENSE-2.0.txt'
                        }
                    }
                    developers {
                        developer {
                            id = 'instrap'
                            name = 'Madrapps'
                            email = 'madrasappfactory@gmail.com'
                        }
                        // More developers if any...
                    }

                    scm {
                        connection = GIT_URL
                        developerConnection = GIT_URL
                        url = SITE_URL
                    }
                }
            }
        }
    }
}

signing {
    useInMemoryPgpKeys(
            System.getenv("OSS_SIGNING_KEY_ID"),
            System.getenv("OSS_SIGNING_KEY"),
            System.getenv("OSS_SIGNING_PASSWORD"),
    )
    sign publishing.publications
}

• Now add the below to your build.gradle at your module level

ext {
    GROUP_ID = "com.github.madrapps" // your project id registered in Sonatype
    ARTIFACT_ID = "plot" // name of your library
    VERSION = "0.1.1"
    SITE_URL = 'https://github.com/Madrapps/plot'
    GIT_URL = 'https://github.com/Madrapps/plot.git'
}

apply from: 'publish.gradle'

Publishing your artifact

• Add all the variables below as Environment Variables
  OSS_USERNAME, OSS_PASSWORD, OSS_STAGING_PROFILE_ID, OSS_SIGNING_KEY_ID, OSS_SIGNING_KEY and OSS_SIGNING_PASSWORD

• Build your project first using ./gradlew build
• Execute ./gradlew publishReleasePublicationToSonatypeRepository to publish your artifact to Staging Repositories in your Sonatype account. From here you can publish your artifact using the Sonatype UI itself (you will have to close and then release the repository in Staging Repositories). Or, you can execute the below command to do that from your terminal.
• Execute ./gradlew closeAndReleaseSonatypeStagingRepository to publish from staging to production.

Working Project

For a working example, please refer to the plot android project. It also has the CI/CD configured using Github Actions. Go crazy!