path: root/projects/net.wotonomy.foundation/src/main/java/net/wotonomy/foundation/internal/Duplicator.java

/*
Wotonomy: OpenStep design patterns for pure Java applications.
Copyright (C) 2001 Michael Powers

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, see http://www.gnu.org
*/

package net.wotonomy.foundation.internal;

import net.wotonomy.foundation.*;

import java.io.*;
import java.util.*; //collections

/**
 * Duplicator makes use of Introspector to duplicate objects, either by shallow
 * copy, deep copy, or by copying properties from one object to apply to another
 * object. You may find this class useful because java.lang.Object.clone() only
 * supports shallow copying.
 *
 * @author michael@mpowers.net
 * @author $Author: cgruber $
 * @version $Revision: 895 $
 */

public class Duplicator {
	/**
	 * Used to represent null values for properties in the maps returned by
	 * readProperties and cloneProperties and in the parameter to writeProperties.
	 * This actually references the NSNull instance.
	 */
	public static final Object NULL = NSNull.nullValue();
	private static NSSelector clone = new NSSelector("clone");

	/**
	 * Returns a list of properties for the specified class that are both readable
	 * and writable.
	 */
	static public List<String> editablePropertiesForObject(Object anObject) {
		List<String> readProperties = new ArrayList<>();
		String[] read = Introspector.getReadPropertiesForObject(anObject);
		for (int i = 0; i < read.length; i++) {
			readProperties.add(read[i]);
		}

		List<String> properties = new ArrayList<>();
		String[] write = Introspector.getWritePropertiesForObject(anObject);
		for (int i = 0; i < write.length; i++) {
			properties.add(write[i]);
		}

		// only use properties on both lists: read/write
		properties.retainAll(readProperties);

		return properties;
	}

	/**
	 * Returns a Map containing only the mutable properties for the specified object
	 * and their values. Any null values for properties will be represented with the
	 * NULL object.
	 */
	static public Map<String, Object> readPropertiesForObject(Object anObject) {
		NSMutableDictionary<String, Object> result = new NSMutableDictionary<>();

		String key;
		Object value;
		Iterator<String> it = editablePropertiesForObject(anObject).iterator();
		while (it.hasNext()) {
			key = it.next().toString();
			value = Introspector.get(anObject, key);
			if (value == null)
				value = NULL;
			result.setObjectForKey(value, key);
		}
		return result;
	}

	/**
	 * Returns a Map containing only the mutable properties for the specified object
	 * and deep clones of their values. Nulls are represented by the NULL object.
	 */
	static public Map<String, Object> clonePropertiesForObject(Object anObject) {
		String key;
		Object value;
		
		Map<String, Object> result = readPropertiesForObject(anObject);
		Iterator<String> it = result.keySet().iterator();
		while (it.hasNext()) {
			key = it.next();
			value = result.get(key);
			value = deepClone(value);
			result.put(key, value);
		}
		return result;
	}

	/**
	 * Applies the map of properties and values to the specified object. Null values
	 * for properties must be represented by the NULL object.
	 */
	static public void writePropertiesForObject(Map<String, Object> aMap, Object anObject) {
		String key;
		Object value;
		Iterator<String> it = aMap.keySet().iterator();
		while (it.hasNext()) {
			key = it.next().toString();
			value = aMap.get(key);
			if (NULL.equals(value))
				value = null;
			Introspector.set(anObject, key, value);
		}
	}

	/**
	 * Creates a new copy of the specified object. This implementation tries to call
	 * clone(), and failing that, calls newInstance and then calls copy() to
	 * transfer the values.
	 * 
	 * @throws WotonomyException if any operation fails.
	 */
	static public Object clone(Object aSource) {
		Object result = null;
		if (clone.implementedByObject(aSource)) {
			try {
				result = clone.invoke(aSource);
				return result;
			} catch (Exception exc) {
				// fall back on newInstance()
			}
		}

		Class<?> c = aSource.getClass();
		try {
			result = c.getDeclaredConstructor().newInstance();
		} catch (Exception exc) {
			throw new WotonomyException(exc);
		}
		return copy(aSource, result);
	}

	/**
	 * Creates a deep copy of the specified object. Every object in this objects
	 * graph will be duplicated with new instances.
	 * 
	 * @throws WotonomyException if any operation fails.
	 */
	static public Object deepClone(Object aSource) {
		// the only known way to deep copy in
		// java without native code is serialization

		try {
			ByteArrayOutputStream byteOutput = new ByteArrayOutputStream();
			ObjectOutputStream objectOutput = new ObjectOutputStream(byteOutput);

			objectOutput.writeObject(aSource);
			objectOutput.flush();
			objectOutput.close();

			ByteArrayInputStream byteInput = new ByteArrayInputStream(byteOutput.toByteArray());
			ObjectInputStream objectInput = new ObjectInputStream(byteInput);
			return objectInput.readObject();
		} catch (Exception exc) {
			throw new WotonomyException("Error cloning object: " + aSource, exc);
		}
	}

	/**
	 * Copies values from one object to another. Returns the destination object.
	 * 
	 * @throws WotonomyException if any operation fails.
	 */
	static public Object copy(Object aSource, Object aDestination) {
		try {
			writePropertiesForObject(readPropertiesForObject(aSource), aDestination);
		} catch (RuntimeException exc) {
			throw new WotonomyException(exc);
		}
		return aDestination;
	}

	/**
	 * Deeply clones the values from one object and applies them to another object.
	 * Returns the destination object.
	 * 
	 * @throws WotonomyException if any operation fails.
	 */
	static public Object deepCopy(Object aSource, Object aDestination) {
		try {
			writePropertiesForObject(clonePropertiesForObject(aSource), aDestination);
		} catch (RuntimeException exc) {
			throw new WotonomyException(exc);
		}
		return aDestination;
	}
}

/*
 * $Log$ Revision 1.1 2006/02/16 16:52:12 cgruber Add cvsignore crap to find off
 * checking in binary crap.
 *
 * Revision 1.1 2006/02/16 13:22:22 cgruber Check in all sources in
 * eclipse-friendly maven-enabled packages.
 *
 * Revision 1.11 2001/08/22 19:24:26 mpowers Providing a more helpful error
 * message for cloning exceptions.
 *
 * Revision 1.10 2001/03/29 03:30:36 mpowers Refactored duplicator a bit.
 * Disabled MissingPropertyExceptions for now.
 *
 * Revision 1.9 2001/03/28 14:11:23 mpowers Removed debugging printlns.
 *
 * Revision 1.8 2001/03/27 23:25:48 mpowers Basically reverting to the previous
 * version.
 *
 * Revision 1.7 2001/03/06 23:18:13 mpowers Clarified some comments.
 *
 * Revision 1.6 2001/03/01 20:36:35 mpowers Better error handling and better
 * handling of nulls.
 *
 * Revision 1.5 2001/02/27 21:43:40 mpowers Removed NullMarker class in favor of
 * NSNull.
 *
 * Revision 1.4 2001/02/26 22:41:51 mpowers Implemented null placeholder
 * classes. Duplicator now uses NSNull. No longer catching base exception class.
 *
 * Revision 1.3 2001/02/23 21:07:46 mpowers Documented the NULL object.
 *
 * Revision 1.1 2001/02/16 22:51:29 mpowers Now deep-cloning objects passed
 * between editing contexts.
 *
 *
 */