/* * module: pip/java/packing -- Packing strategy objects for converting * Java objects to and from stored data. * class: Packing -- Abstract strategy class for packing/unpacking data * * $Id: Packing.java,v 1.4 1997-10-23 21:09:59+10 mbp Exp $ * Copyright (C) 1997 Pharos IP Pty Ltd * * 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. */ package au.com.pharos.packing; /** A packing Packing defines a method of converting an object to * and from an array of bytes for storage in a database. * *
Generally, each packing Packing should be reflexive: that is, * converting any object to and from an array of bytes should yield * the same object, or an object appropriately equivalent. * *
Some Packing subclasses may not be able to pack all
* objects, or may not be able to unpack an object from some byte
* arrays. For example, only Strings can safely be stored as string
* representations, and not all arrays are valid Java serialization
* forms. In this case, the Packing object should throw an
* IllegalArgumentException
from toBytes()
* or toBytes()
.
*
*
In both cases, null references should be passed through * unchanged. * *
Example: *
* Packing strategy = new StringPacking(); * byte[] raw = strategy.toBytes("Hello world"); * ... store and retrieve raw[] * String result = (String) strategy.fromBytes(raw) ** * * @see au.com.pharos.packing.StringPacking * @see au.com.pharos.packing.NativeStringPacking * @see au.com.pharos.packing.RawPacking * @see au.com.pharos.packing.SerializationPacking * * @version $Revision: 1.4 $ * @author Martin Pool **/ public abstract class Packing { /** Convert an object to an array of bytes. **/ public abstract byte[] toBytes(Object obj) throws IllegalArgumentException; /** Reconstitute an array of bytes into an object. **/ public abstract Object fromBytes(byte[] raw) throws IllegalArgumentException; /** Helper function that generates an IllegalArgumentException */ protected IllegalArgumentException cantConvert(Object obj) { return new IllegalArgumentException ("Can't pack object \"" + obj.toString() + "\" (" + obj.getClass().toString() + ")" + "\n\tusing strategy " + this.toString()); } }