How do I generate maven-metata.xml with maven-publish and the artifactory-gradle-plugin?

Question

I've written a Gradle plugin in groovy and used Gradle to build it. I've got a local network Artifactory server that I publish the results to using the Gradle Artifactory plugin and the maven-publish plugin in Gradle. I have another Gradle build script that relies on this plugin as a dependency. I've been able to get this all working if I list my dependency with a specific version. I've tried to use a maven version range (ex. '[1.0,2.0)'), but this fails saying it can't find maven-metadata.xml. I checked Artifactory, and sure enough, it isn't there. What do I need to do to produce it, preferably during the build of the plugin?

Here is the build.gradle file for my custom gradle plugin:

buildscript {
    repositories {
        maven {
            url "${artifactory_contextUrl}/plugins-release"
            credentials {
                username = "${artifactory_user}"
                password = "${artifactory_password}"
            }
        }
    }
    dependencies {
        classpath group: 'org.apache.directory.studio', name: 'org.apache.commons.io', version: '2.4'
        classpath group: 'org.jfrog.buildinfo', name: 'build-info-extractor-gradle', version: '2.0.9'
    }
}

plugins {
    id 'com.jfrog.artifactory' version '3.0.1'
}

apply plugin: 'groovy'
apply plugin: 'maven-publish'

artifactory {
    contextUrl = "${artifactory_contextUrl}"
    publish {
        repository {
            repoKey = 'plugins-snapshot-local'
            username = "${artifactory_user}"
            password = "${artifactory_password}"
            maven = true
        }
        defaults {
            publications ('mavenJava')
        }
    }
    resolve {
        repository {
            repoKey = 'libs-release'
            username = "${artifactory_user}"
            password = "${artifactory_password}"
            maven = true
        }
    }
}

dependencies {
    compile gradleApi()
    compile localGroovy()
}

publishing {
    publications {
        mavenJava(MavenPublication) {
            from components.java
        }
    }
}

I've searched the Gradle, Artifactory, and Maven documentation to understand maven-metadata.xml and how to generate and deploy. It makes sense what it is, and I could probably build one manually, but I can't find anything that explains specifically how to automatically generate it in Gradle with either the maven-publish plugin or the artifactory-gradle-plugin. I don't want to have to manually update the file since that would defeat the automation effort, and I don't want to switch to mvn since I've already invested so much in Gradle.

Answer 1

A groupId had to be added to the publications section. Once implemented, a maven-metadata.xml file was published to the artifact repository.

publishing {
    publications {
        mavenJava(MavenPublication) {
            groupId = 'com.group'
        }
    }
}

Answer 2

I had the same problem and it turned out that the Artifactory repository was not a Maven repo, it was a Generic repo. It took me forever to notice because I didn't create the repo and I assumed it was a Maven repo, and deploying/resolving otherwise was working as expected.
After switching to a Maven repo, the maven-metadata.xml's were generated upon publishing.