001/*******************************************************************************
002 * This software is provided as a supplement to the authors' textbooks on digital
003 * image processing published by Springer-Verlag in various languages and editions.
004 * Permission to use and distribute this software is granted under the BSD 2-Clause
005 * "Simplified" License (see http://opensource.org/licenses/BSD-2-Clause).
006 * Copyright (c) 2006-2023 Wilhelm Burger, Mark J. Burge. All rights reserved.
007 * Visit https://imagingbook.com for additional details.
008 ******************************************************************************/
009package imagingbook.common.util;
010
011import java.io.BufferedInputStream;
012import java.io.BufferedOutputStream;
013import java.io.File;
014import java.io.FileInputStream;
015import java.io.FileOutputStream;
016import java.io.IOException;
017import java.io.InputStream;
018import java.io.ObjectInput;
019import java.io.ObjectInputStream;
020import java.io.ObjectOutput;
021import java.io.ObjectOutputStream;
022import java.io.OutputStream;
023
024/**
025 * Helper class providing static methods for writing/reading serialized data to/from files. It is recommended to
026 * serialize only data structures composed of standard Java types. Otherwise, if self-defined classes are reloaded,
027 * classes of previously serialized objects may not match any more, causing a {@link ClassNotFoundException} to be
028 * thrown.
029 *
030 * @author WB
031 * @version 2022/07/28
032 */
033public abstract class SerializationHelper {
034        
035        // This class is not supposed to be instantiated.
036        private SerializationHelper() {}
037
038        /**
039         * Writes a serialized representation of an arbitrary Java object to a file.
040         *
041         * @param obj the object to be serialized.
042         * @param file the file to write to.
043         * @return the full path of the written file.
044         */
045        public static String writeObject(Object obj, File file) {
046                String path = file.getAbsolutePath();
047                try (FileOutputStream strm = new FileOutputStream(file);
048                         OutputStream buffer = new BufferedOutputStream(strm);
049                         ObjectOutput output = new ObjectOutputStream(buffer);) 
050                {
051                        output.writeObject(obj);
052                } catch (IOException e) {
053                        System.err.println(e.toString());
054                        return null;
055                }
056                return path;
057        }
058
059        /**
060         * Reads an object from a serialization file. The return value must be cast to the appropriate type, which must be
061         * known.
062         *
063         * @param file the file to read.
064         * @return the object reconstructed from the file representation or null if unsuccessful.
065         */
066        public static Object readObject(File file) {
067                Object obj = null;
068                try (InputStream strm = new FileInputStream(file);
069                         InputStream buffer = new BufferedInputStream(strm);
070                         ObjectInput input = new ObjectInputStream(buffer);) 
071                {
072                        obj = input.readObject();
073                } catch (ClassNotFoundException | IOException e) {
074                        System.err.println(e.toString());
075                        return null;
076                }
077                return obj;
078        }
079
080}