Creating an offline Maven repository with Gradle

OfflineMavenRepository.groovy

package org.gradle.training

import org.gradle.api.tasks.Input
import org.gradle.api.tasks.OutputDirectory
import org.gradle.api.tasks.TaskAction
import org.gradle.api.DefaultTask
import org.gradle.util.GFileUtils
import org.gradle.api.artifacts.Configuration
import org.gradle.api.artifacts.component.ModuleComponentIdentifier
import org.gradle.maven.MavenModule
import org.gradle.maven.MavenPomArtifact

class OfflineMavenRepository extends DefaultTask {    
    @Input
    String configurationName = 'compile'
    
    @OutputDirectory
    File repoDir = new File(project.buildDir, 'offline-repo')
    
    @TaskAction
    void build() {
        Configuration configuration = project.configurations.getByName(configurationName)
        copyJars(configuration)
        copyPoms(configuration)
    }
    
    private void copyJars(Configuration configuration) {
        configuration.resolvedConfiguration.resolvedArtifacts.each { artifact ->
            def moduleVersionId = artifact.moduleVersion.id
            File moduleDir = new File(repoDir, "${moduleVersionId.group}/${moduleVersionId.name}/${moduleVersionId.version}")
            GFileUtils.mkdirs(moduleDir)
            GFileUtils.copyFile(artifact.file, new File(moduleDir, artifact.file.name))
        }
    }
    
    private void copyPoms(Configuration configuration) {
        def componentIds = configuration.incoming.resolutionResult.allDependencies.collect { it.selected.id }

        def result = project.dependencies.createArtifactResolutionQuery()
            .forComponents(componentIds)
            .withArtifacts(MavenModule, MavenPomArtifact)
            .execute()

        for(component in result.resolvedComponents) {
            def componentId = component.id
            
            if(componentId instanceof ModuleComponentIdentifier) {
                File moduleDir = new File(repoDir, "${componentId.group}/${componentId.module}/${componentId.version}")
                GFileUtils.mkdirs(moduleDir)                
                File pomFile = component.getArtifacts(MavenPomArtifact)[0].file
                GFileUtils.copyFile(pomFile, new File(moduleDir, pomFile.name))
            }          
        }
    }
}

This misses getting the parent poms and boms which prevents you from using this to gather all dependencies to run Gradle in offline mode.

For those struggling with the issue lukecwik brought up, check out uklance's solution on GitHub. He has created a plugin that pulls in all the dependencies.