Android aar deployment in Maven - 2022

Introduction

If you are working on android library project, you might be wondering how to publish it on Maven like this. Earlier it was done using Android studio plugin maven, but with gradle v 7.0+ it does not work. Now we have to use maven-publish. This post gives you more insights of this procedure.

Generally, there are two types of repositories: local and remote.

A local repository is the repository Maven creates on the computer it is building on. It is usually located under the $HOME/.m2/repository directory.

	ls -l ~/.m2/repository/com/swapnilutilities/swapnilCalculator/0.0.1
	swapnilCalculator-0.0.1-javadoc.jar swapnilCalculator-0.0.1-sources.jar swapnilCalculator-0.0.1.aar swapnilCalculator-0.0.1.module swapnilCalculator-0.0.1.pom

view raw localMavenCache.txt hosted with ❤ by GitHub

Remote repository is located on maven server. When any user wants to use our library, they will enter groupId and version of library they want to use.
We will create and deploy a new android aar artifact on maven.
The process can be summarized as
1. Create Account and repository on Nexus sonatype
2. Configure gradle to create, sign and upload aar file to sonatype.
3. Let sonatype verify the artifacts as per maven requirement (Close operation)
4. Release artifacts to maven.

Let's go through the steps one by one.

1. Create account on sonatype at https://issues.sonatype.org/secure/Dashboard.jspa. Register new project by creating new jira ticket. It will create new repository in sonatype
Create → Create Issue → Community Support - Open Source Project Repository Hosting → New Project → with groupid io.bitbucket.swapnilcpublic e.g. OSSRH-85813

2. You will be asked to prove that you own the domain mentioned in Jira ticket. (e.g. https://bitbucket.org/swapnilcpublic). You will be asked to place a file or create git repo under the domain to prove that it really belongs to you. Since I do not own a domain name, I created empty bitbucket repo under bitbucket repo. Here ossrh-85813 is the JIRA ticket id. For more details follow how-to-set-txt-record and personal groupId. If required a static web site can be created using bitbucket.

3. Signing: One of the requirements for publishing your artifacts to the Central Repository, is that they have been signed with PGP. Here is how tosetup signing with gpg.
Create new key with details like

Name: SwapnilGpg
Email: email@id.com
Pass: password

After creation, see created keys with

	gpg --list-keys
	/Users/swapnilchaudhari/.gnupg/pubring.kbx
	------------------------------------------
	pub rsa4096 2022-11-10 [SC] [expires: 2026-11-10]
	0D879958847AD37E72FECF1
	uid [ultimate] SwapnilGpg <email@id.com>
	sub rsa4096 2022-11-10 [E] [expires: 2026-11-10]

view raw blog_gpg_list_key.txt hosted with ❤ by GitHub

Export secret keys using

gpg --keyring secring.gpg --export-secret-keys > ~/.gnupg/secring.gpg

view raw blog_gpg_export_keys.txt hosted with ❤ by GitHub

We need short key. It will be referred from gradle script. It appears after `rsa4096/` in output. Find short KeyId using

	gpg --list-keys --keyid-format SHORT
	pub rsa4096/E72FECF1 2022-11-10 [SC]
	80B74D9C1E696BA2C0D879958847AD37E72FECF1

view raw blog_gpg_short_key.txt hosted with ❤ by GitHub

Once the GPG keys are generated, publish these keys to an open key server. Run the following command to do so. YYYYYYYY is the short key generated using previous step (E72FECF1 in my case).

	gpg --keyserver hkp://keyserver.ubuntu.com --send-keys YYYYYYYY
	gpg --keyserver hkp://pgp.mit.edu --send-keys YYYYYYYY

view raw blog_gpg_make_key_public.txt hosted with ❤ by GitHub

Verify these keys using

gpg --keyserver hkp://pgp.mit.edu --search-keys email@id.com

view raw blog_gpg_verify_public_keys.txt hosted with ❤ by GitHub

4. Update build.gradle in ProjectRoot/swapnilCalculator/build.gradle with following

	plugins {
	...
	id 'maven-publish'
	id 'signing'
	}
	android {
	...
	publishing {
	singleVariant('release') {
	withSourcesJar()
	withJavadocJar()
	}
	}
	}
	signing {
	publishing.publications.all { publication ->
	sign publication
	}
	}
	afterEvaluate {
	publishing {
	publications {
	release(MavenPublication) {
	groupId = GROUP
	artifactId = POM_ARTIFACT_ID
	version = VERSION_NAME
	afterEvaluate {
	from components.release
	}
	pom {
	name = POM_ARTIFACT_ID
	description = POM_DESCRIPTION
	url = POM_URL
	properties = [
	versionCode: VERSION_CODE
	]
	licenses {
	license {
	name = POM_LICENCE_NAME
	url = POM_LICENCE_URL
	}
	}
	developers {
	developer {
	id = POM_DEVELOPER_ID
	name = POM_DEVELOPER_NAME
	email = POM_DEVELOPER_EMAIL
	}
	}
	scm {
	connection = POM_SCM_CONNECTION
	developerConnection = POM_SCM_DEV_CONNECTION
	url = POM_URL
	}
	}
	}
	}
	repositories {
	maven {
	def releasesRepoUrl = "https://s01.oss.sonatype.org/service/local/staging/deploy/maven2/"
	def snapshotsRepoUrl = "https://s01.oss.sonatype.org/content/repositories/snapshots/"
	url = version.endsWith('SNAPSHOT') ? snapshotsRepoUrl : releasesRepoUrl
	credentials {
	username NEXUS_USERNAME
	password NEXUS_PASSWORD
	}
	authentication {
	basic(BasicAuthentication)
	}
	}
	}
	}
	}

view raw blog_maven_gradle.txt hosted with ❤ by GitHub

5. Add details below in ProjectRoot/gradle.properties

	signing.keyId=<short key of GPG>E72FECF1
	signing.password=<GPG Password>
	signing.secretKeyRingFile=/Users/swapnilchaudhari/.gnupg/secring.gpg
	NEXUS_USERNAME=<Sonatype User ID>
	NEXUS_PASSWORD=<Sonatype Password>
	VERSION_NAME=0.0.2
	VERSION_CODE=2
	GROUP=io.bitbucket.swapnilcpublic
	#POM details
	POM_DESCRIPTION=Library for adding 2 integers.
	POM_URL=https://swapnilcpublic.bitbucket.io/
	POM_SCM_URL=https://swap_chau@bitbucket.org/swap_chau/sonatypelibraryrepo/
	POM_SCM_CONNECTION=scm:git@bitbucket.com:swap_chau/sonatypelibraryrepo.git
	POM_SCM_DEV_CONNECTION=scm:git@bitbucket.com:swap_chau/sonatypelibraryrepo.git
	POM_LICENCE_NAME=The Apache Software License, Version 2.0
	POM_LICENCE_URL=http://www.apache.org/licenses/LICENSE-2.0.txt
	POM_LICENCE_DIST=repo
	POM_DEVELOPER_ID=<Sonatype User ID>
	POM_DEVELOPER_NAME=Swapnil Chaudhari
	POM_DEVELOPER_EMAIL=email@id.com

view raw blog_maven_gradle_properties.txt hosted with ❤ by GitHub

In ProjectRoot/swapnilCalculator/gradle.properties

	POM_NAME=Swapnil Calculator Library
	POM_ARTIFACT_ID=swapnilCalculator
	POM_PACKAGING=aar

view raw blog_maven_module_gradle_properties.txt hosted with ❤ by GitHub

6. Upload aar, jar and signatures using
./gradlew clean publishReleasePublicationToMavenRepository After a successful deployment to OSSRH your components are stored in a separate, temporary repository, that is private to your projects members. In order to get these components published you will have to 'close' & release' them. 'Close' operation checks whether all artifacts are as specified by Maven. 'Close' operation takes few minutes to finish. Once that is successful, proceed with 'release' operation. If there is error, please resolve them and re-upload the library.
After uploading & releasing all artifacts, it takes 4-10 hours for maven to show the library.

7. Find the published library using

1. Sonatype staging repository
2. Maven repository
3. Maven repository
4. Sonatype staging repository
5. Sonatype nexus

8. References

1. https://gist.github.com/lopspower/6f62fe1492726d848d6d
2. https://central.sonatype.org/publish/
3. https://central.sonatype.org/publish/requirements/coordinates/
4. https://central.sonatype.org/publish/publish-guide/
5. https://shahsurajk.medium.com/technical-publishing-aars-to-maven-central-7e9c603f9ea1
6. https://www.baeldung.com/maven-snapshot-release-repository
7. https://docs.gradle.org/current/userguide/signing_plugin.html#sec:signatory_credentials
8. https://docs.gradle.org/current/userguide/publishing_maven.html