01: /*
02: * $Id: RowComparator.java,v 1.14 2004/08/27 03:21:19 ahimanikya Exp $
03: * =======================================================================
04: * Copyright (c) 2002-2004 Axion Development Team. All rights reserved.
05: *
06: * Redistribution and use in source and binary forms, with or without
07: * modification, are permitted provided that the following conditions
08: * are met:
09: *
10: * 1. Redistributions of source code must retain the above
11: * copyright notice, this list of conditions and the following
12: * disclaimer.
13: *
14: * 2. Redistributions in binary form must reproduce the above copyright
15: * notice, this list of conditions and the following disclaimer in
16: * the documentation and/or other materials provided with the
17: * distribution.
18: *
19: * 3. The names "Tigris", "Axion", nor the names of its contributors may
20: * not be used to endorse or promote products derived from this
21: * software without specific prior written permission.
22: *
23: * 4. Products derived from this software may not be called "Axion", nor
24: * may "Tigris" or "Axion" appear in their names without specific prior
25: * written permission.
26: *
27: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28: * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29: * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
30: * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
31: * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
32: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
33: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
37: * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
38: * =======================================================================
39: */
40:
41: package org.axiondb;
42:
43: import java.util.Comparator;
44:
45: import org.axiondb.util.ExceptionConverter;
46:
47: /**
48: * A {@link Comparator}for {@link Row Rows}, which will sort a collection according to
49: * the value of a single selectable. By using a ComparatorChain, one can perform in-memory
50: * sorts over multiple columns.
51: *
52: * @author Morgan Delagrange
53: * @author Rodney Waldhoff
54: * @author Ahimanikya Satapathy
55: */
56: public class RowComparator implements Comparator {
57: public RowComparator(Selectable sel, RowDecorator dec) {
58: _sel = sel;
59: _dec = dec;
60: _cmp = _sel.getDataType();
61: }
62:
63: public int compare(Object o1, Object o2) {
64: Object column1 = evaluate(o1);
65: Object column2 = evaluate(o2);
66: int eval = 0;
67: if (null == column1) {
68: if (null == column2) {
69: eval = 0;
70: } else {
71: eval = 1;
72: }
73: } else if (null == column2) {
74: eval = -1;
75: } else {
76: eval = _cmp.compare(column1, column2);
77: }
78: return eval;
79: }
80:
81: private Object evaluate(Object obj) {
82: try {
83: _dec.setRow(-1, (Row) obj);
84: return _sel.evaluate(_dec);
85: } catch (ClassCastException castEx) {
86: throw new RuntimeException("Expected Row, found " + obj);
87: } catch (Exception e) {
88: throw ExceptionConverter.convertToRuntimeException(e);
89: }
90: }
91:
92: private Comparator _cmp = null;
93: private RowDecorator _dec = null;
94: private Selectable _sel = null;
95: }
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