content: /*
   *    This program is free software; you can redistribute it and/or modify
   *    it under the terms of the GNU General Public License as published by
   *    the Free Software Foundation; either version 2 of the License, or
   *    (at your option) any later version.
   *
   *    This program 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 General Public License for more details.
   *
   *    You should have received a copy of the GNU General Public License
   *    along with this program; if not, write to the Free Software
   *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  /*
   * SerializationHelper.java
   * Copyright (C) 2007 University of Waikato, Hamilton, New Zealand
   */
  
  package weka.core;
  
  import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.InputStream;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.ObjectStreamClass;
  import java.io.OutputStream;
  import java.io.Serializable;
  import java.util.Vector;
  
  /**
   * A helper class for determining serialVersionUIDs and checking whether
   * classes contain one and/or need one. One can also serialize and deserialize
   * objects to and fro files or streams.
   * 
   * @author  fracpete (fracpete at waikato dot ac dot nz)
   * @version $Revision: 6230 $
   */
  public class SerializationHelper
    implements RevisionHandler {
  
    /** the field name of serialVersionUID. */
    public final static String SERIAL_VERSION_UID = "serialVersionUID";
    
    /**
     * checks whether a class is serializable.
     * 
     * @param classname	the class to check
     * @return		true if the class or one of its ancestors implements
     * 			the Serializable interface, otherwise false (also if 
     * 			the class cannot be loaded)
     */
    public static boolean isSerializable(String classname) {
      boolean	result;
      
      try {
        result = isSerializable(Class.forName(classname));
      }
      catch (Exception e) {
        result = false;
      }
        
      return result;
    }
    
    /**
     * checks whether a class is serializable.
     * 
     * @param c		the class to check
     * @return		true if the class or one of its ancestors implements
     * 			the Serializable interface, otherwise false
     */
    public static boolean isSerializable(Class c) {
      return ClassDiscovery.hasInterface(Serializable.class, c);
    }
    
    /**
     * checks whether the given class contains a serialVersionUID.
     * 
     * @param classname	the class to check
     * @return		true if the class contains a serialVersionUID, 
     * 			otherwise false (also if the class is not
     * 			implementing serializable or cannot be loaded)
     */
    public static boolean hasUID(String classname) {
      boolean	result;
      
      try {
        result = hasUID(Class.forName(classname));
      }
      catch (Exception e) {
        result = false;
      }
      
      return result;
    }
  
    /**
     * checks whether the given class contains a serialVersionUID.
     * 
     * @param c		the class to check
     * @return		true if the class contains a serialVersionUID, 
     * 			otherwise false (also if the class is not
     * 			implementing serializable)
     */
    public static boolean hasUID(Class c) {
      boolean	result;
      
      result = false;
      
      if (isSerializable(c)) {
        try {
  	c.getDeclaredField(SERIAL_VERSION_UID);
  	result = true;
        }
        catch (Exception e) {
  	result = false;
        }
      }
      
      return result;
    }
    
    /**
     * checks whether a class needs to declare a serialVersionUID, i.e., it
     * implements the java.io.Serializable interface but doesn't declare a
     * serialVersionUID.
     * 
     * @param classname	the class to check
     * @return		true if the class needs to declare one, false otherwise
     * 			(also if the class cannot be loaded!)
     */
    public static boolean needsUID(String classname) {
      boolean	result;
      
      try {
        result = needsUID(Class.forName(classname));
      }
      catch (Exception e) {
        result = false;
      }
      
      return result;
    }
    
    /**
     * checks whether a class needs to declare a serialVersionUID, i.e., it
     * implements the java.io.Serializable interface but doesn't declare a
     * serialVersionUID.
     * 
     * @param c		the class to check
     * @return		true if the class needs to declare one, false otherwise
     */
    public static boolean needsUID(Class c) {
      boolean	result;
      
      if (isSerializable(c))
        result = !hasUID(c);
      else
        result = false;
      
      return result;
    }
    
    /**
     * reads or creates the serialVersionUID for the given class.
     * 
     * @param classname	the class to get the serialVersionUID for
     * @return		the UID, 0L for non-serializable classes (or if the
     * 			class cannot be loaded)
     */
    public static long getUID(String classname) {
      long	result;
      
      try {
        result = getUID(Class.forName(classname));
      }
      catch (Exception e) {
        result = 0L;
      }
      
      return result;
    }
    
    /**
     * reads or creates the serialVersionUID for the given class.
     * 
     * @param c		the class to get the serialVersionUID for
     * @return		the UID, 0L for non-serializable classes
     */
    public static long getUID(Class c) {
      return ObjectStreamClass.lookup(c).getSerialVersionUID();
    }
  
    /**
     * serializes the given object to the specified file.
     * 
     * @param filename	the file to write the object to
     * @param o		the object to serialize
     * @throws Exception	if serialization fails
     */
    public static void write(String filename, Object o) throws Exception {
      write(new FileOutputStream(filename), o);
    }
  
    /**
     * serializes the given object to the specified stream.
     * 
     * @param stream	the stream to write the object to
     * @param o		the object to serialize
     * @throws Exception	if serialization fails
     */
    public static void write(OutputStream stream, Object o) throws Exception {
      ObjectOutputStream	oos;
      
      if (!(stream instanceof BufferedOutputStream))
        stream = new BufferedOutputStream(stream);
      
      oos = new ObjectOutputStream(stream);
      oos.writeObject(o);
      oos.flush();
      oos.close();
    }
  
    /**
     * serializes the given objects to the specified file.
     * 
     * @param filename	the file to write the object to
     * @param o		the objects to serialize
     * @throws Exception	if serialization fails
     */
    public static void writeAll(String filename, Object[] o) throws Exception {
      writeAll(new FileOutputStream(filename), o);
    }
  
    /**
     * serializes the given objects to the specified stream.
     * 
     * @param stream	the stream to write the object to
     * @param o		the objects to serialize
     * @throws Exception	if serialization fails
     */
    public static void writeAll(OutputStream stream, Object[] o) throws Exception {
      ObjectOutputStream	oos;
      int			i;
      
      if (!(stream instanceof BufferedOutputStream))
        stream = new BufferedOutputStream(stream);
      
      oos = new ObjectOutputStream(stream);
      for (i = 0; i < o.length; i++)
        oos.writeObject(o[i]);
      oos.flush();
      oos.close();
    }
  
    /**
     * deserializes the given file and returns the object from it.
     * 
     * @param filename	the file to deserialize from
     * @return		the deserialized object
     * @throws Exception	if deserialization fails
     */
    public static Object read(String filename) throws Exception {
      return read(new FileInputStream(filename));
    }
  
    /**
     * deserializes from the given stream and returns the object from it.
     * 
     * @param stream	the stream to deserialize from
     * @return		the deserialized object
     * @throws Exception	if deserialization fails
     */
    public static Object read(InputStream stream) throws Exception {
      ObjectInputStream 	ois;
      Object		result;
      
      if (!(stream instanceof BufferedInputStream))
        stream = new BufferedInputStream(stream);
      
      ois    = new ObjectInputStream(stream);
      result = ois.readObject();
      ois.close();
      
      return result;
    }
  
    /**
     * deserializes the given file and returns the objects from it.
     * 
     * @param filename	the file to deserialize from
     * @return		the deserialized objects
     * @throws Exception	if deserialization fails
     */
    public static Object[] readAll(String filename) throws Exception {
      return readAll(new FileInputStream(filename));
    }
  
    /**
     * deserializes from the given stream and returns the object from it.
     * 
     * @param stream	the stream to deserialize from
     * @return		the deserialized object
     * @throws Exception	if deserialization fails
     */
    public static Object[] readAll(InputStream stream) throws Exception {
      ObjectInputStream 	ois;
      Vector<Object>	result;
      
      if (!(stream instanceof BufferedInputStream))
        stream = new BufferedInputStream(stream);
      
      ois    = new ObjectInputStream(stream);
      result = new Vector<Object>();
      try {
        while (true) {
  	result.add(ois.readObject());
        }
      }
      catch (Exception e) {
        // ignored
      }
      ois.close();
      
      return result.toArray(new Object[result.size()]);
    }
    
    /**
     * Returns the revision string.
     * 
     * @return		the revision
     */
    public String getRevision() {
      return RevisionUtils.extract("$Revision: 6230 $");
    }
    
    /**
     * Outputs information about a class on the commandline, takes class
     * name as arguments.
     * 
     * @param args	the classnames to check
     * @throws Exception	if something goes wrong
     */
    public static void main(String[] args) throws Exception {
      if (args.length == 0) {
        System.out.println("\nUsage: " + SerializationHelper.class.getName() + " classname [classname [classname [...]]]\n");
        System.exit(1);
      }
      
      // check all the classes
      System.out.println();
      for (int i = 0; i < args.length; i++) {
        System.out.println(args[i]);
        System.out.println("- is serializable: " + isSerializable(args[i]));
        System.out.println("- has " + SERIAL_VERSION_UID + ": " + hasUID(args[i]));
        System.out.println("- needs " + SERIAL_VERSION_UID + ": " + needsUID(args[i]));
        System.out.println("- " + SERIAL_VERSION_UID + ": private static final long serialVersionUID = " + getUID(args[i]) + "L;");
        System.out.println();
      }
    }
  }
  