| 1 | /*
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| 2 | * module: pip/java/packing -- Packing strategy objects for converting
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| 3 | * Java objects to and from stored data.
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| 4 | * class: Packing -- Abstract strategy class for packing/unpacking data
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| 5 | *
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| 6 | * $Id: Packing.java 10737 2005-10-19 03:06:40Z kjdon $
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| 7 | * Copyright (C) 1997 Pharos IP Pty Ltd
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| 8 | *
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| 9 | * This program is free software; you can redistribute it and/or modify
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| 10 | * it under the terms of the GNU General Public License as published by
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| 11 | * the Free Software Foundation; either version 2 of the License, or
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| 12 | * (at your option) any later version.
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| 13 | *
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| 14 | * This program is distributed in the hope that it will be useful,
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| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 17 | * GNU General Public License for more details.
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| 18 | *
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| 19 | * You should have received a copy of the GNU General Public License
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| 20 | * along with this program; if not, write to the Free Software
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| 21 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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| 22 | */
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| 23 |
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| 24 | package au.com.pharos.packing;
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| 25 |
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| 26 | /** A packing Packing defines a method of converting an object to
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| 27 | * and from an array of bytes for storage in a database.
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| 28 | *
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| 29 | * <P>Generally, each packing Packing should be reflexive: that is,
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| 30 | * converting any object to and from an array of bytes should yield
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| 31 | * the same object, or an object appropriately equivalent.
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| 32 | *
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| 33 | * <P>Some Packing subclasses may not be able to pack all
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| 34 | * objects, or may not be able to unpack an object from some byte
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| 35 | * arrays. For example, only Strings can safely be stored as string
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| 36 | * representations, and not all arrays are valid Java serialization
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| 37 | * forms. In this case, the Packing object should throw an
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| 38 | * <code>IllegalArgumentException</code> from <code>toBytes()</code>
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| 39 | * or <code>toBytes()</code>.
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| 40 | *
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| 41 | * <P>In both cases, null references should be passed through
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| 42 | * unchanged.
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| 43 | *
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| 44 | * <P>Example:
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| 45 | * <PRE>
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| 46 | * Packing strategy = new StringPacking();
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| 47 | * byte[] raw = strategy.toBytes("Hello world");
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| 48 | * ... store and retrieve raw[]
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| 49 | * String result = (String) strategy.fromBytes(raw)
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| 50 | * </PRE>
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| 51 | *
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| 52 | *
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| 53 | * @see au.com.pharos.packing.StringPacking
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| 54 | * @see au.com.pharos.packing.NativeStringPacking
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| 55 | * @see au.com.pharos.packing.RawPacking
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| 56 | * @see au.com.pharos.packing.SerializationPacking
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| 57 | *
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| 58 | * @version $Revision: 10737 $
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| 59 | * @author Martin Pool
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| 60 | **/
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| 61 | public abstract class Packing {
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| 62 | /** Convert an object to an array of bytes. **/
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| 63 | public abstract byte[] toBytes(Object obj) throws IllegalArgumentException;
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| 64 |
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| 65 | /** Reconstitute an array of bytes into an object. **/
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| 66 | public abstract Object fromBytes(byte[] raw) throws IllegalArgumentException;
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| 67 |
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| 68 | /** Helper function that generates an IllegalArgumentException */
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| 69 | protected IllegalArgumentException cantConvert(Object obj) {
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| 70 | return new IllegalArgumentException
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| 71 | ("Can't pack object \"" + obj.toString() +
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| 72 | "\" (" + obj.getClass().toString() + ")" +
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| 73 | "\n\tusing strategy " + this.toString());
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| 74 | }
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| 75 | }
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| 76 |
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| 77 |
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