code: /* LanguageTool, a natural language style checker 
   * Copyright (C) 2016 Daniel Naber (http://www.danielnaber.de)
   * 
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
   * USA
   */
  package org.languagetool.gui;
  
  import java.beans.XMLDecoder;
  import java.beans.XMLEncoder;
  import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.commons.lang3.SystemUtils;
  
  /**
   * Helper class to store configuration
   *
   * @author Panagiotis Minos
   * @since 3.4
   */
  class LocalStorage {
  
    private static final String VENDOR_ID = "languagetool.org";
    private static final String APPLICATION_ID = "LanguageTool";
    
    private final File directory;
  
    LocalStorage() {
      String userHome = null;
      try {
        userHome = System.getProperty("user.home");
      } catch (SecurityException ex) {
      }
      if (userHome == null) {
        directory = null;
      } else if (SystemUtils.IS_OS_WINDOWS) {
        File appDataDir = null;
        try {
          String appData = System.getenv("APPDATA");
          if (!StringUtils.isEmpty(appData)) {
            appDataDir = new File(appData);
          }
        } catch (SecurityException ex) {
        }
        if (appDataDir != null && appDataDir.isDirectory()) {
          String path = VENDOR_ID + "\\" + APPLICATION_ID + "\\";
          directory = new File(appDataDir, path);
        } else {
          String path = "Application Data\\" + VENDOR_ID + "\\" + APPLICATION_ID + "\\";
          directory = new File(userHome, path);
        }
      } else if (SystemUtils.IS_OS_LINUX) {
        File appDataDir = null;
        try {
          String xdgConfigHome = System.getenv("XDG_CONFIG_HOME");
          if (!StringUtils.isEmpty(xdgConfigHome)) {
            appDataDir = new File(xdgConfigHome);
            if (!appDataDir.isAbsolute()) {
              //https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
              //All paths set in these environment variables must be absolute.
              //If an implementation encounters a relative path in any of these
              //variables it should consider the path invalid and ignore it.
              appDataDir = null;
            }
          }
        } catch (SecurityException ex) {
        }
        if (appDataDir != null && appDataDir.isDirectory()) {
          String path = APPLICATION_ID + "/";
          directory = new File(appDataDir, path);
        } else {
          String path = ".config/" + APPLICATION_ID + "/";
          directory = new File(userHome, path);
        }
      } else if (SystemUtils.IS_OS_MAC_OSX) {
        String path = "Library/Application Support/" + APPLICATION_ID + "/";
        directory = new File(userHome, path);
      } else {
        String path = "." + APPLICATION_ID + "/";
        directory = new File(userHome, path);
      }
      if (directory != null && !directory.exists()) {
        directory.mkdirs();
      }
    }
  
    void saveProperty(String name, Object obj) {
      if (directory == null) {
        return;
      }
      synchronized(directory) {
        try (XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(
              new FileOutputStream(new File(directory, name))))) {
          encoder.writeObject(obj);
        } catch (FileNotFoundException ex) {
          Tools.showError(ex);
        }
      }
    }
  
    <T> T loadProperty(String name, Class<T> clazz) {
      if (directory == null) {
        return null;
      }
      synchronized(directory) {
        try (XMLDecoder decoder = new XMLDecoder(new BufferedInputStream(
              new FileInputStream(new File(directory, name))))) {
          try {
            return clazz.cast(decoder.readObject());
          } catch (ClassCastException ex) {
            Tools.showError(ex);
            return null;
          } catch (Exception ex) {
            //probably user messed up with files
            Tools.showError(ex);
            return null;
          }
        } catch (FileNotFoundException ex) {
          //ignore, we have not saved yet a property with this name
        }
      }
      return null;
    }
  
  }
  