code: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF 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.apache.skywalking.oap.server.library.util;
  
  import java.io.File;
  import java.io.FileNotFoundException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.Reader;
  import java.net.URL;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Path;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Objects;
  
  public class ResourceUtils {
  
      public static Reader read(String fileName) throws FileNotFoundException {
          return new InputStreamReader(readToStream(fileName), StandardCharsets.UTF_8);
      }
  
      public static InputStream readToStream(String fileName) throws FileNotFoundException {
          URL url = ResourceUtils.class.getClassLoader().getResource(fileName);
          if (url == null) {
              throw new FileNotFoundException("file not found: " + fileName);
          }
          return ResourceUtils.class.getClassLoader().getResourceAsStream(fileName);
      }
  
      public static File[] getPathFiles(String path) throws FileNotFoundException {
          URL url = ResourceUtils.class.getClassLoader().getResource(path);
          if (url == null) {
              throw new FileNotFoundException("path not found: " + path);
          }
          return Arrays.stream(Objects.requireNonNull(new File(url.getPath()).listFiles(), "No files in " + path))
                       .filter(File::isFile).toArray(File[]::new);
      }
  
      /**
       * @param directoryPath the directory path
       * @param maxDepth      the max directory depth to get the files, the given directory is 0 as the tree root
       * @return all normal files which in this directory and subDirectory according to the maxDepth
       * @throws FileNotFoundException the directory not exist in the given path
       */
      public static List<File> getDirectoryFilesRecursive(String directoryPath,
                                                          int maxDepth) throws FileNotFoundException {
  
          URL url = ResourceUtils.class.getClassLoader().getResource(directoryPath);
          if (url == null) {
              throw new FileNotFoundException("path not found: " + directoryPath);
          }
          List<File> fileList = new ArrayList<>();
          return getDirectoryFilesRecursive(url.getPath(), fileList, maxDepth);
      }
  
      private static List<File> getDirectoryFilesRecursive(String directoryPath, List<File> fileList, int maxDepth) {
          if (maxDepth < 0) {
              return fileList;
          }
          maxDepth--;
          File file = new File(directoryPath);
          if (file.isDirectory()) {
              File[] subFiles = file.listFiles();
              if (subFiles != null) {
                  for (File subFile : subFiles) {
                      if (subFile.isDirectory()) {
                          getDirectoryFilesRecursive(subFile.getPath(), fileList, maxDepth);
                      } else {
                          fileList.add(subFile);
                      }
                  }
              }
          }
          return fileList;
      }
  
      public static Path getPath(String path) {
          return new File(Objects.requireNonNull(ResourceUtils.class.getClassLoader().getResource(path)).getPath()).toPath();
      }
  }
  