1 /*
2 * $Source: /usr/cvsroot/melati/poem/src/main/java/org/melati/poem/CachedTailoredQuery.java,v $
3 * $Revision: 1.17 $
4 *
5 * Copyright (C) 2000 William Chesters
6 *
7 * Part of Melati (http://melati.org), a framework for the rapid
8 * development of clean, maintainable web applications.
9 *
10 * Melati is free software; Permission is granted to copy, distribute
11 * and/or modify this software under the terms either:
12 *
13 * a) the GNU General Public License as published by the Free Software
14 * Foundation; either version 2 of the License, or (at your option)
15 * any later version,
16 *
17 * or
18 *
19 * b) any version of the Melati Software License, as published
20 * at http://melati.org
21 *
22 * You should have received a copy of the GNU General Public License and
23 * the Melati Software License along with this program;
24 * if not, write to the Free Software Foundation, Inc.,
25 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the
26 * GNU General Public License and visit http://melati.org to obtain the
27 * Melati Software License.
28 *
29 * Feel free to contact the Developers of Melati (http://melati.org),
30 * if you would like to work out a different arrangement than the options
31 * outlined here. It is our intention to allow Melati to be used by as
32 * wide an audience as possible.
33 *
34 * This program is distributed in the hope that it will be useful,
35 * but WITHOUT ANY WARRANTY; without even the implied warranty of
36 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 * GNU General Public License for more details.
38 *
39 * Contact details for copyright holder:
40 *
41 * William Chesters <williamc At paneris.org>
42 * http://paneris.org/~williamc
43 * Obrechtstraat 114, 2517VX Den Haag, The Netherlands
44 */
45
46 package org.melati.poem;
47
48 import java.util.Enumeration;
49 import java.util.Vector;
50 import org.melati.poem.util.EnumUtils;
51
52 /**
53 * A cached instance of a {@link PreparedTailoredQuery}.
54 *
55 * @author WilliamC At paneris.org
56 *
57 */
58 public class CachedTailoredQuery extends PreparedTailoredQuery {
59
60 private Vector<FieldSet> results = null;
61 private Vector<Object> firstRawResults = null;
62 private long[] tableSerials;
63
64 /**
65 * Full Constructor.
66 *
67 * @param modifier SQL modifier eg DISTINCT
68 * @param selectedColumns An array of columns we know we need
69 * @param otherTables Tables other than ours whose modification
70 * state needs to be taken into account
71 * @param whereClause Raw SQL
72 * @param orderByClause Raw ORDER BY clause
73 */
74 public CachedTailoredQuery(String modifier,
75 Column<?>[] selectedColumns, Table<?>[] otherTables,
76 String whereClause, String orderByClause) {
77 super(modifier, selectedColumns, otherTables, whereClause, orderByClause);
78 tableSerials = new long[tables.length];
79 }
80
81 /**
82 * Constructor with modifier null.
83 *
84 * @param selectedColumns An array of columns we know we need
85 * @param otherTables Tables other than ours whose modification
86 * state needs to be taken into account
87 * @param whereClause Raw SQL
88 * @param orderByClause Raw ORDER BY clause
89 */
90 public CachedTailoredQuery(Column<?>[] selectedColumns, Table<?>[] otherTables,
91 String whereClause, String orderByClause) {
92 this(null, selectedColumns, otherTables, whereClause, orderByClause);
93 }
94
95 /**
96 * @return whether the underlying tables have changed since last run.
97 */
98 protected boolean upToDate() {
99 boolean is = true;
100
101 PoemTransaction transaction = PoemThread.transaction();
102 for (int t = 0; t < tables.length; ++t) {
103 long currentSerial = tables[t].serial(transaction);
104 if (tableSerials[t] != currentSerial) {
105 is = false;
106 tableSerials[t] = currentSerial;
107 }
108 }
109
110 return is;
111 }
112
113 /**
114 * {@inheritDoc}
115 * @see org.melati.poem.TailoredQuery#selection()
116 */
117 public Enumeration<FieldSet> selection() {
118 Vector<FieldSet> resultsLocal = this.results;
119 if (!upToDate() || resultsLocal == null) {
120 this.results = EnumUtils.vectorOf(super.selection());
121 resultsLocal = this.results;
122 }
123 return resultsLocal.elements();
124 }
125
126 /**
127 * {@inheritDoc}
128 * @see org.melati.poem.TailoredQuery#selection_firstRaw()
129 */
130 public Enumeration<Object> selection_firstRaw() {
131 Vector<Object> firstRawResultsLocal = this.firstRawResults;
132 if (!upToDate() || firstRawResultsLocal == null) {
133 this.firstRawResults =
134 EnumUtils.vectorOf(super.selection_firstRaw());
135 firstRawResultsLocal = this.firstRawResults;
136 }
137 return firstRawResultsLocal.elements();
138 }
139 }