code: /*
   * Copyright 2012-2018 Chronicle Map Contributors
   *
   * 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.
   */
  
  package net.openhft.chronicle.hash.impl.util;
  
  import net.openhft.chronicle.map.ChronicleMapBuilder;
  import shaded.org.apache.maven.model.Model;
  import shaded.org.apache.maven.model.io.xpp3.MavenXpp3Reader;
  
  import java.io.*;
  import java.nio.charset.StandardCharsets;
  
  /**
   * gets the version of the current build
   */
  public final class BuildVersion {
  
      private static String version = null;
  
      private BuildVersion() {
      }
  
      public static void main(String[] args) {
          System.out.println(version());
      }
  
      /**
       * @return version of ChronicleMap being used, or NULL if its not known
       */
      public synchronized static String version() {
  
          if (version != null) {
              return version;
          }
  
          try {
              // the best way to get the version is to read the map.version file
              InputStream resource = BuildVersion.class.getClassLoader().getResourceAsStream("map" +
                      ".version");
              BufferedReader in = new BufferedReader(new InputStreamReader(resource, StandardCharsets.UTF_8));
  
              version = in.readLine().trim();
              if (!"${project.version}".equals(version()))
                  return version;
  
              return version;
          } catch (Exception e) {
              // do nothing
          }
  
          // another way to get the version is to read it from the manifest
          final String versionFromManifest = getVersionFromManifest();
  
          if (versionFromManifest != null) {
              version = versionFromManifest;
              return version;
          }
  
          // as a fall back for development, we will read the version from the pom file
          version = getVersionFromPom();
          return version;
      }
  
      /**
       * This should be used by everyone that has install chronicle map as a JAR
       *
       * @return gets the version out of the manifest, or null if it can not be read
       */
      private static String getVersionFromManifest() {
          return ChronicleMapBuilder.class.getPackage().getImplementationVersion();
      }
  
      /**
       * reads the pom file to get this version, only to be used for development or within the IDE.
       *
       * @return gets the version from the pom.xml
       */
      private static String getVersionFromPom() {
  
          final String absolutePath = new File(BuildVersion.class.getResource(BuildVersion.class
                  .getSimpleName() + ".class").getPath())
                  .getParentFile().getParentFile().getParentFile().getParentFile().getParentFile()
                  .getParentFile().getParentFile().getAbsolutePath();
  
          final File file = new File(absolutePath + "/pom.xml");
  
          try (InputStreamReader reader = new InputStreamReader(new FileInputStream(file), StandardCharsets.UTF_8)) {
  
              final MavenXpp3Reader xpp3Reader = new MavenXpp3Reader();
              Model model = xpp3Reader.read(reader);
              return model.getVersion();
  
          } catch (NoClassDefFoundError e) {
              // if you want to get the version possibly in development add in to your pom
              // pax-url-aether.jar
              return null;
          } catch (Exception e) {
              return null;
          }
      }
  }