code: protected void downloadPlugin(File pluginFile, PluginCoordinates coordinates) {
          // First check the .m2 directory
          File m2Dir = PluginUtils.getUserM2Repository();
          if (m2Dir != null) {
              File artifactFile = PluginUtils.getM2Path(m2Dir, coordinates);
              if (artifactFile.isFile()) {
                  try {
                      FileUtils.copyFile(artifactFile, pluginFile);
                      return;
                  } catch (IOException e) {
                      artifactFile.delete();
                      throw new RuntimeException(e);
                  }
              }
          }
  
          // Didn't find it in .m2, so try downloading it.
          Set<URI> repositories = getMavenRepositories();
          for (URI mavenRepoUrl : repositories) {
              if (downloadFromMavenRepo(pluginFile, coordinates, mavenRepoUrl)) {
                  return;
              }
          }
      }
docs: Downloads the plugin via its maven GAV information.  This will first look in the local
  .m2 directory.  If the plugin is not found there, then it will try to download the
  plugin from one of the configured remote maven repositories.