code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you 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.
  
  package org.openqa.selenium.firefox;
  
  import com.google.common.io.Resources;
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.net.URL;
  import org.openqa.selenium.WebDriverException;
  import org.openqa.selenium.io.FileHandler;
  
  public class ClasspathExtension implements Extension {
    private final Class<?> loadResourcesUsing;
    private final String loadFrom;
  
    public ClasspathExtension(Class<?> loadResourcesUsing, String loadFrom) {
      this.loadResourcesUsing = loadResourcesUsing;
      this.loadFrom = loadFrom;
    }
  
    @Override
    public void writeTo(File extensionsDir) throws IOException {
      if (!FileHandler.isZipped(loadFrom)) {
        throw new WebDriverException("Will only install zipped extensions for now");
      }
  
      File holdingPen = new File(extensionsDir, "webdriver-staging");
      FileHandler.createDir(holdingPen);
  
      File extractedXpi = new File(holdingPen, loadFrom);
      File parentDir = extractedXpi.getParentFile();
      if (!parentDir.exists()) {
        if (!parentDir.mkdirs()) {
          throw new IOException("Unable to create directory for extracted extension");
        }
      }
  
      URL resourceUrl = Resources.getResource(loadResourcesUsing, loadFrom);
  
      try (OutputStream stream = new FileOutputStream(extractedXpi)) {
        Resources.copy(resourceUrl, stream);
      }
      new FileExtension(extractedXpi).writeTo(extensionsDir);
    }
  }
  