download jenkins plugin and dependencies offline for the internal jenkins server cannot access internet.

JenkinsPluginDownloader.scala

import java.io.FileOutputStream
import java.net.URL
import java.nio.channels.{Channels, ReadableByteChannel}
import java.util.Scanner
import java.util.zip.ZipFile

object JenkinsPluginDownloader {
  def main(args: Array[String]): Unit = {
    if(args.length < 2) {
      println(s"usage: scala JenkinsPluginDownloader junit 1.19")
      System.exit(1)
    }
    val name = args(0)
    val version = args(1)
    downloadPlugin(name, version)
  }

  def downloadPlugin(name: String, version: String): Unit = {
    val url = s"http://updates.jenkins-ci.org/download/plugins/$name/$version/${name}.hpi"
    val fileUrl = new URL(url)
    println(s"downloading from: $url")
    val rbc: ReadableByteChannel = Channels.newChannel(fileUrl.openStream())
    val file = s"${name}.hpi"
    val fos = new FileOutputStream(file)
    fos.getChannel().transferFrom(rbc, 0, Long.MaxValue)
    downloadDependency(file)
  }

  def downloadDependency(file: String): Unit = {
    val zipFile = new ZipFile(file)
    val entry = zipFile.getEntry("META-INF/MANIFEST.MF")
    val inputStream = zipFile.getInputStream(entry)
    val context = new Scanner(inputStream).useDelimiter("\\A").next()
    val dependencies = context.split("\n").filter(_.contains("Plugin-Dependencies")).map(_.split(":"))
    dependencies.foreach(v => downloadPlugin(v(1).trim, v(2).trim))
  }

}