How can I get gradle to populate jars with dependency metadata? - gradle

Question

So if I build a jar in Maven, say for example jackson-core-2.5.1.jar, I find the following in the artifact:
META-INF/maven/
META-INF/maven/com.fasterxml.jackson.core/
META-INF/maven/com.fasterxml.jackson.core/jackson-core/
META-INF/maven/com.fasterxml.jackson.core/jackson-core/pom.properties
META-INF/maven/com.fasterxml.jackson.core/jackson-core/pom.xml
Gradle, however, does not seem to create this data. Problem is that we have several components of our build, including a parent project, that aren't hosted in the same SCM location. For our large and complex build, how would Gradle know that a locally built artifact in one SCM location depends on a locally built artifact in another, if there's no metadata? What is the Gradle way to manage this situation?

Answer 1

Repositories contain a separate copy of pom.xml. It usually lives next to the JAR file in the physical structure on the disk. This applies to binary repositories like Nexus or Artifatory and also to your local Maven repository (under $HOME/.m2/repo).
If for some reason you want to copy the behavior of Maven you can tell Gradle to do create those files. We use this customization in subprojects closure that configures our multi-project Gradle build.
jar {
// until we have better solution
// https://discuss.gradle.org/t/jar-task-does-not-see-dependency-when-using-maven-publish/11091
if (project.tasks.findByName('generatePomFileForMavenJavaPublication')) {
dependsOn 'generatePomFileForMavenJavaPublication'
} else {
project.tasks.whenTaskAdded { addedTask ->
if (addedTask.name == 'generatePomFileForMavenJavaPublication') {
project.tasks.jar.dependsOn 'generatePomFileForMavenJavaPublication'
}
}
}
into("META-INF/maven/$project.group/$project.archivesBaseName") {
/*
from generatePomFileForMavenJavaPublication
*/
from new File(project.buildDir, 'publications/mavenJava')
rename ".*", "pom.xml"
}
}
It would be simpler if there wasn't a problem with generatePomFileForMavenJavaPublication task being created lazily sometimes. And you need to check how to create your properties file. I guess you can dump properties from a running Gradle process there.