code: /*
   * Copyright 2007-present the original author or authors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  import java.net.*;
  import java.io.*;
  import java.nio.channels.*;
  import java.util.Properties;
  
  public class MavenWrapperDownloader {
  
      private static final String WRAPPER_VERSION = "0.5.6";
      /**
       * Default URL to download the maven-wrapper.jar from, if no 'downloadUrl' is provided.
       */
      private static final String DEFAULT_DOWNLOAD_URL = "https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/"
          + WRAPPER_VERSION + "/maven-wrapper-" + WRAPPER_VERSION + ".jar";
  
      /**
       * Path to the maven-wrapper.properties file, which might contain a downloadUrl property to
       * use instead of the default one.
       */
      private static final String MAVEN_WRAPPER_PROPERTIES_PATH =
              ".mvn/wrapper/maven-wrapper.properties";
  
      /**
       * Path where the maven-wrapper.jar will be saved to.
       */
      private static final String MAVEN_WRAPPER_JAR_PATH =
              ".mvn/wrapper/maven-wrapper.jar";
  
      /**
       * Name of the property which should be used to override the default download url for the wrapper.
       */
      private static final String PROPERTY_NAME_WRAPPER_URL = "wrapperUrl";
  
      public static void main(String args[]) {
          System.out.println("- Downloader started");
          File baseDirectory = new File(args[0]);
          System.out.println("- Using base directory: " + baseDirectory.getAbsolutePath());
  
          // If the maven-wrapper.properties exists, read it and check if it contains a custom
          // wrapperUrl parameter.
          File mavenWrapperPropertyFile = new File(baseDirectory, MAVEN_WRAPPER_PROPERTIES_PATH);
          String url = DEFAULT_DOWNLOAD_URL;
          if(mavenWrapperPropertyFile.exists()) {
              FileInputStream mavenWrapperPropertyFileInputStream = null;
              try {
                  mavenWrapperPropertyFileInputStream = new FileInputStream(mavenWrapperPropertyFile);
                  Properties mavenWrapperProperties = new Properties();
                  mavenWrapperProperties.load(mavenWrapperPropertyFileInputStream);
                  url = mavenWrapperProperties.getProperty(PROPERTY_NAME_WRAPPER_URL, url);
              } catch (IOException e) {
                  System.out.println("- ERROR loading '" + MAVEN_WRAPPER_PROPERTIES_PATH + "'");
              } finally {
                  try {
                      if(mavenWrapperPropertyFileInputStream != null) {
                          mavenWrapperPropertyFileInputStream.close();
                      }
                  } catch (IOException e) {
                      // Ignore ...
                  }
              }
          }
          System.out.println("- Downloading from: " + url);
  
          File outputFile = new File(baseDirectory.getAbsolutePath(), MAVEN_WRAPPER_JAR_PATH);
          if(!outputFile.getParentFile().exists()) {
              if(!outputFile.getParentFile().mkdirs()) {
                  System.out.println(
                          "- ERROR creating output directory '" + outputFile.getParentFile().getAbsolutePath() + "'");
              }
          }
          System.out.println("- Downloading to: " + outputFile.getAbsolutePath());
          try {
              downloadFileFromURL(url, outputFile);
              System.out.println("Done");
              System.exit(0);
          } catch (Throwable e) {
              System.out.println("- Error downloading");
              e.printStackTrace();
              System.exit(1);
          }
      }
  
      private static void downloadFileFromURL(String urlString, File destination) throws Exception {
          if (System.getenv("MVNW_USERNAME") != null && System.getenv("MVNW_PASSWORD") != null) {
              String username = System.getenv("MVNW_USERNAME");
              char[] password = System.getenv("MVNW_PASSWORD").toCharArray();
              Authenticator.setDefault(new Authenticator() {
                  @Override
                  protected PasswordAuthentication getPasswordAuthentication() {
                      return new PasswordAuthentication(username, password);
                  }
              });
          }
          URL website = new URL(urlString);
          ReadableByteChannel rbc;
          rbc = Channels.newChannel(website.openStream());
          FileOutputStream fos = new FileOutputStream(destination);
          fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
          fos.close();
          rbc.close();
      }
  
  }
  