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The Waikato Environment for Knowledge Analysis (WEKA), a machine learning workbench. This version represents the developer version, the "bleeding edge" of development, you could say. New functionality gets added to this version.

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/*
 *   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 3 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, see .
 */

/*
 * SerializationHelper.java
 * Copyright (C) 2007-2012 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.IOException;
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 $Revision$
 */
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 InheritanceUtils.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 result;

    if (!(stream instanceof BufferedInputStream)) {
      stream = new BufferedInputStream(stream);
    }

    ois = new ObjectInputStream(stream);
    result = new Vector();
    try {
      while (true) {
        result.add(ois.readObject());
      }
    } catch (IOException e) {
      // ignored
    }
    ois.close();

    return result.toArray(new Object[result.size()]);
  }

  /**
   * Returns the revision string.
   * 
   * @return the revision
   */
  @Override
  public String getRevision() {
    return RevisionUtils.extract("$Revision$");
  }

  /**
   * 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 (String arg : args) {
      System.out.println(arg);
      System.out.println("- is serializable: " + isSerializable(arg));
      System.out.println("- has " + SERIAL_VERSION_UID + ": " + hasUID(arg));
      System.out
        .println("- needs " + SERIAL_VERSION_UID + ": " + needsUID(arg));
      System.out.println("- " + SERIAL_VERSION_UID
        + ": private static final long serialVersionUID = " + getUID(arg)
        + "L;");
      System.out.println();
    }
  }
}
 















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