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.core;
  
  import java.io.File;
  import java.net.MalformedURLException;
  import java.net.URISyntaxException;
  import java.net.URL;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Locate the base work path of OAP backend.
   */
  public class WorkPath {
      private static final Logger LOGGER = LoggerFactory.getLogger(WorkPath.class);
  
      private static File PATH;
  
      public static File getPath() {
          if (PATH == null) {
              PATH = findPath();
          }
          return PATH;
      }
  
      private static File findPath() {
          String classResourcePath = WorkPath.class.getName().replaceAll("\\.", "/") + ".class";
  
          URL resource = ClassLoader.getSystemClassLoader().getResource(classResourcePath);
          if (resource != null) {
              String urlString = resource.toString();
  
              LOGGER.debug("The beacon class location is {}.", urlString);
  
              int insidePathIndex = urlString.indexOf('!');
              boolean isInJar = insidePathIndex > -1;
  
              if (isInJar) {
                  urlString = urlString.substring(urlString.indexOf("file:"), insidePathIndex);
                  File agentJarFile = null;
                  try {
                      agentJarFile = new File(new URL(urlString).toURI());
                  } catch (MalformedURLException e) {
                      throw new UnexpectedException("Can not locate oap core jar file by url:" + urlString, e);
                  } catch (URISyntaxException e) {
                      throw new UnexpectedException("Can not locate oap core jar file by url:" + urlString, e);
                  }
                  if (agentJarFile.exists()) {
                      return agentJarFile.getParentFile();
                  }
              } else {
                  int prefixLength = "file:".length();
                  String classLocation = urlString.substring(prefixLength, urlString.length() - classResourcePath.length());
                  return new File(classLocation);
              }
          }
  
          throw new UnexpectedException("Can not locate oap core jar file by path:" + classResourcePath);
      }
  }
  