DataObject


1   /*
2    * Copyright (c) 2003 - 2007 OpenSubsystems s.r.o. Slovak Republic. All rights reserved.
3    * 
4    * Project: OpenSubsystems
5    * 
6    * $Id: DataObject.java,v 1.9 2007/01/07 06:14:17 bastafidli Exp $
7    * 
8    * This program is free software; you can redistribute it and/or modify
9    * it under the terms of the GNU General Public License as published by
10   * the Free Software Foundation; version 2 of the License. 
11   * 
12   * This program is distributed in the hope that it will be useful,
13   * but WITHOUT ANY WARRANTY; without even the implied warranty of
14   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   * GNU General Public License for more details.
16   * 
17   * You should have received a copy of the GNU General Public License
18   * along with this program; if not, write to the Free Software
19   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
20   */
21  
22  package org.opensubsystems.core.data;
23  
24  import java.io.Serializable  ;
25  
26  /**
27   * Base class for all data objects regardless of how they are persisted.
28   * Data object is here to implement Transfer Object pattern as described
29   * in http://java.sun.com/blueprints/corej2eepatterns/Patterns/TransferObject.html
30   * The main goal is to encapsulate set of related attributes as one object
31   * so they can be easily passed between different modules and tiers. 
32   *
33   * @version $Id: DataObject.java,v 1.9 2007/01/07 06:14:17 bastafidli Exp $
34   * @author Miro Halas
35   * @code.reviewer Miro Halas
36   * @code.reviewed 1.6 2005/09/07 16:32:31 alkalimero
37   */
38  public abstract class DataObject implements Serializable  
39  {
40     // Constants ////////////////////////////////////////////////////////////////
41  
42     /**
43      * ID used when creating new object for which the real ID wasn't generated yet.
44      * HSQLDB at some time autogenerated first entry as 0 and it wasn't possible
45      * to change it. Therefore we used -1 as value which won't be generated by DB.
46      * Then HSQLDB made it configurable but I was afraid that -1 was already used 
47      * at some places as hardcoded value and not at constant that it is too risky 
48      * to change it to 0 (which is what would it be if the value it not initialized)
49      */
50     public static final int NEW_ID = -1;
51  
52     /**
53      * Object representation for easy reuse.
54      */
55     public static final Integer   NEW_ID_OBJ = new Integer  (NEW_ID);
56     
57     /**
58      * String representation for easy reuse.
59      */
60     public static final String   NEW_ID_STR = Integer.toString(NEW_ID);
61     
62     // Attributes ///////////////////////////////////////////////////////////////
63  
64     /**
65      * Flag which is set to true if this data was loaded from some persistance 
66      * store, e.g. database and false if it was constructed in memory and it is
67      * not persisted.
68      */
69     private boolean m_bFromPersistanceStore = false;
70  
71     // Accessors ////////////////////////////////////////////////////////////////
72  
73     /**
74      * Check if this record was loaded from some persistence store  and therefore 
75      * it is existing data object which was already created in the persistence 
76      * store or it came from somewhere else (was created in memory).
77      *
78      * @return boolean
79      */
80     public boolean isFromPersistenceStore(
81     )
82     {
83        return m_bFromPersistanceStore;
84     }
85  
86     /**
87      * Set flag that this record was loaded from some persistance store.
88      */
89     public void setFromPersistenceStore(
90     )
91     {
92        m_bFromPersistanceStore = true;
93     }
94  
95     /**
96      * Get the id uniquely identifying the object.
97      * 
98      * @return int
99      */
100    public abstract int getId(
101    );
102 
103    /**
104     * Get the id as object uniquely identifying the object. This method allows
105     * to  the implementing class to cache this object if desired to improve
106     * performance.
107     * 
108     * @return Integer
109     */
110    public abstract Integer   getIdAsObject(
111    ); 
112    
113    /**
114     * Method to compare all data attributes of two objects to figure out, if
115     * their attributes are the same. The objects can for example differ by database 
116     * generated id and creation or modification timestamp but if other properties
117     * which represents the real data are the same then the objects are considered
118     * to be the same. This is weaker constraint that equals since not all 
119     * attributes has to be the same, only the one which really represents the
120     * business data should match.
121     * 
122     * @param oObject - Object to compare
123     * @return boolean - true if same, false otherwise
124     */
125    public abstract boolean isSame(
126       Object   oObject
127    );
128 }
129
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