/*
* 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.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;
/**
* 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: 1.1 $
*/
public class SerializationHelper {
/** 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;
oos = new ObjectOutputStream(stream);
oos.writeObject(o);
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;
ois = new ObjectInputStream(stream);
result = ois.readObject();
ois.close();
return result;
}
/**
* Outputs information about a class on the commandline, takes class
* name as arguments
*
* @param args the classnames to check
*/
public static void main(String[] args) {
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();
}
}
}