BeanComparator


1   /**
2    * JOnAS: Java(TM) Open Application Server
3    * Copyright (C) 1999 Bull S.A.
4    * Contact: jonas-team@objectweb.org
5    *
6    * This library is free software; you can redistribute it and/or
7    * modify it under the terms of the GNU Lesser General Public
8    * License as published by the Free Software Foundation; either
9    * version 2.1 of the License, or any later version.
10   *
11   * This library is distributed in the hope that it will be useful,
12   * but WITHOUT ANY WARRANTY; without even the implied warranty of
13   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   * Lesser General Public License for more details.
15   *
16   * You should have received a copy of the GNU Lesser General Public
17   * License along with this library; if not, write to the Free Software
18   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
19   * USA
20   *
21   * --------------------------------------------------------------------------
22   * $Id: BeanComparator.java,v 1.2 2004/06/11 08:16:53 danesa Exp $
23   * --------------------------------------------------------------------------
24   */
25  
26  package org.objectweb.jonas.webapp.jonasadmin.common;
27  
28  import java.util.Comparator  ;
29  
30  import org.apache.commons.beanutils.PropertyUtils;
31  
32  /**
33   * BeanComparator is a comparator for beans.
34   * It's used to compare a bean with its own properties or with its own string value
35   * (return by the <code>toString()</code> method).
36   *
37   * @author Michel-Ange ANTON
38   */
39  
40  public class BeanComparator implements Comparator   {
41  
42  // --------------------------------------------------------- Instance Variables
43  
44      private String  [] m_Orders = null;
45  
46  // --------------------------------------------------------- Constructors
47  
48      /**
49       * Comparator by default (use the <code>toString()</code> methods).
50       */
51      public BeanComparator() {
52          m_Orders = null;
53      }
54  
55      /**
56       * Comparator in order of the properties.
57       *
58       * @param p_Orders A array of the names of the properties
59       */
60      public BeanComparator(String  [] p_Orders) {
61          m_Orders = p_Orders;
62      }
63  
64  // --------------------------------------------------------- Public Methods
65  
66      /**
67       * Compare two beans instances.
68       *
69       * @param p_O1 The first bean to compare
70       * @param p_O2 The second bean to compare
71       * @return 0 if equals, < 0 if first bean lower than second bean, > 0 if first bean upper than second bean.
72       */
73      public int compare(Object   p_O1, Object   p_O2) {
74          if (m_Orders != null) {
75              return compareOrder(p_O1, p_O2);
76          }
77          return compareDefault(p_O1, p_O2);
78      }
79  
80      /**
81       * Indentical bean.
82       *
83       * @param p_Obj The bean to compare.
84       * @return True if identical.
85       */
86      public boolean equals(Object   p_Obj) {
87          if (this.getClass().getName().equals(p_Obj.getClass().getName())) {
88              return (compare(this, p_Obj) == 0);
89          }
90          return false;
91      }
92  
93      /**
94       * Compare the null of two objects.
95       *
96       * @param p_O1 The first object to compare
97       * @param p_O2 The second object to compare
98       * @return 0 if the two are null or the two not null, < 0 if second object is null, > 0 if first object is null.
99       */
100     public static int compareNull(Object   p_O1, Object   p_O2) {
101         int iRet = 0;
102         if (p_O1 != p_O2) {
103             if (p_O1 == null) {
104                 iRet = 1;
105             }
106             else if (p_O2 == null) {
107                 iRet = -1;
108             }
109         }
110         return iRet;
111     }
112 
113     /**
114      * Compare two strings with the ignore case
115      * but if is identical, compare normaly with case.
116      *
117      * @param p_O1 The first string to compare
118      * @param p_O2 The second string to compare
119      * @return 0 if equals, < 0 if first string lower than second string, > 0 if first string upper than second string.
120      */
121     public static int compareString(String   p_S1, String   p_S2) {
122         int iRet = compareNull(p_S1, p_S2);
123         if (iRet == 0) {
124             try {
125                 iRet = p_S1.compareToIgnoreCase(p_S2);
126                 if (iRet == 0) {
127                     iRet = p_S1.compareTo(p_S2);
128                 }
129             }
130             catch (NullPointerException   e) {
131                 iRet = 0;
132             }
133         }
134         return iRet;
135     }
136 
137 // --------------------------------------------------------- Protected Methods
138 
139     /**
140      * Compare the beans like a string (used the <code>toString()</code> method of the object).
141      * Used when order is unknown.
142      *
143      * @param p_O1 The first bean to compare
144      * @param p_O2 The second bean to compare
145      * @return 0 if equals, < 0 if first bean lower than second bean, > 0 if first bean upper than second bean.
146      */
147     protected int compareDefault(Object   p_O1, Object   p_O2) {
148         int iRet = compareNull(p_O1, p_O2);
149         if (iRet == 0) {
150             iRet = compareString(p_O1.toString(), p_O2.toString());
151         }
152         return iRet;
153     }
154 
155     /**
156      * Compare the beans with the properties in order given.
157      * Used when order is known.
158      *
159      * @param p_O1 The first bean to compare
160      * @param p_O2 The second bean to compare
161      * @return 0 if equals, < 0 if first bean lower than second bean, > 0 if first bean upper than second bean.
162      */
163     protected int compareOrder(Object   p_O1, Object   p_O2) {
164         int iRet = 0;
165         Object   oValue1, oValue2;
166         try {
167             for (int i = 0; i < m_Orders.length; i++) {
168                 // Get values
169                 oValue1 = PropertyUtils.getProperty(p_O1, m_Orders[i]);
170                 oValue2 = PropertyUtils.getProperty(p_O2, m_Orders[i]);
171                 // Compare
172                 iRet = compareNull(oValue1, oValue2);
173                 if (iRet == 0) {
174                     try {
175                         iRet = compareString(oValue1.toString(), oValue2.toString());
176                     }
177                     catch (NullPointerException   e) {
178                         iRet = 0;
179                     }
180                 }
181                 // Continue in order if always equals
182                 if (iRet != 0) {
183                     break;
184                 }
185             }
186         }
187         catch (Exception   e) {
188             System.err.println("[" + e.getClass().getName() + "] " + e.getMessage());
189             iRet = 0;
190         }
191         return iRet;
192     }
193 }
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