Introduction

Yesterday JFrog announced that Bintray/JCenter will go away in three months. Although they do provide free JFrog Platform Cloud subscriptions for Open Source developers, and I got one, I do not see how I can use it to distribute my artifacts. Besides, as I wrote before, Bintray seems to be abandonware…

I am not ready to switch to the non-traditional JitPack (yet?), so Maven Central seems to be the way to go.

One reason I did not use it before because it has a reputation of being slow, and the way it is struggling, returns 405 Not Allowed and keeps being restarted right now, just a day after the JCenter announcement, seems to confirm that. At least they report the status of things :) I hope that with everybody moving there maybe Sombody Will Do Something about it and eventually things will improve.

Another reason I didn’t use it before is: it is supposed to be more difficult to use than JCenter, with all their signing requirements and such. This turned out to be not that hard ;)

These are my notes on what did I have to do to switch to Maven Central. Official (but somewhat outdated) documentation is available:

Account

I signed up for Sonatype at https://issues.sonatype.org/secure/Signup!default.jspa with dub@podval.org email address. The same credentials are used at https://oss.sonatype.org/ (OSSRH) and for deploying artifacts. To make them available to Gradle, I put them into ~/.gradle/gradle.properties:

mavenCentralUsername=dub
mavenCentralPassword=...

To the publishing block of the Gradle build file I added:

repositories {
  maven {
    name = 'mavenCentral'
    url = version.endsWith('SNAPSHOT') ?
      'https://oss.sonatype.org/content/repositories/snapshots' :
      'https://oss.sonatype.org/service/local/staging/deploy/maven2'

    credentials {
      username = mavenCentralUsername
      password = mavenCentralPassword
    }
  }
}

Namespace

I claimed the “namespace” (group id) org.podval.tools by opening a special kind of ticket via https://issues.sonatype.org/secure/CreateIssue.jspa?issuetype=21&pid=10134

I had to verify that I own the domain podval.org by adding a DNS TXT record referencing the ticket. I did ask if I should claim org.podval instead of the org.podval.tools, but it seems that nobody read my question - probably because initial verification is handled by robots :). But I then asked specifically to wide the scope of my “staging profile” that resulted from this ticket, and Joel Orlina did it immediately!

In addition to podval.org, I control the domain (and GitHub organization) opentorah.org. I want to sign artifacts in it with a key associated with an appropriate email address dub@opentorah.org. It seems that Maven Central verification does not require for the signing key to be associated with email address of the Sonatype account, so I didn’t have to create another Sonatype account, and claimed the org.opentorah namespace under the same one!

GPG Keys and Signing

I do not normally use (or have) a GPG key, so I had to make one (actually, two). First, I made sure that permissions on the ~/.gnupg are tight:

$ chown -R $(whoami) ~/.gnupg/
$ chmod 700 ~/.gnupg/*
$ chmod 700 ~/.gnupg

(Some advice on the Internet suggests 600, but it is wrong: gpg2 won’t be able to read the secret keys…)

Generated GPG key for dub@podval.org:

$ gpg2 --generate-key ... whatwhen

Sent the public key to the keyserver so that Maven Central could verify it:

$ gpg2 --keyserver keys.gnupg.net --send-key EA493E02

That didn’t seem to work, so I manually submitted at http://pool.sks-keyservers.net the output of

$ gpg2 --armor --export dub@podval.org

All the above was repeated for a dub@opentorah.org key.

By default, Gradle’s Signing Plugin uses properties (signing.keyId, signing.password, signing.secretKeyRingFile) to access the key. I prefer to use explicit configuration, but more importantly, I need the flexibility to use different keys to sign the artifacts of different projects.

I got the keys into a form suitable for gradle.properties: run

$ gpg2 --armor --export-secret-keys dub@podval.org | awk '1' ORS='\\n\\\n'

and removed the final \n\.

I then added to ~/.gradle/gradle.properties:

gnupg.dub-podval-org.key=<see above>
gnupg.dub-podval-org.password=...
gnupg.dub-opentorah-org.key=<see above>
gnupg.dub-opentorah-org.password=...

To the Gradle build file, I added:

signing {
  useInMemoryPgpKeys(
    getProperty('gnupg.dub-podval-org.key'),
    getProperty('gnupg.dub-podval-org.password')
  )
  sign publishing.publications.library
}

Releasing

After artifacts are deployed to the staging repository:

  • log into Nexus at https://oss.sonatype.org/
  • “close” the staging repository (verify that their requirements are satisfied)
  • “release” it

If this is a first release in this namespace, comment on the namespace claim ticket so that Sonatype can start synchronizing the artifacts to Maven Central. Formy second namespace I received this reply:

Central sync is activated for org.opentorah. After you successfully release, your component will be published to Central, typically within 10 minutes, though updates to search.maven.org can take up to two hours.

In this context, “Central” means https://repo1.maven.org/maven2/

TODO nexus Gradle plugin(s) //id ‘io.codearte.nexus-staging’ version ‘0.22.0’ ? or something else that gets credentials from maven-publish?