001: /* ====================================================================
002: * The QueryForm License, Version 1.1
003: *
004: * Copyright (c) 1998 - 2003 David F. Glasser. All rights
005: * reserved.
006: *
007: * Redistribution and use in source and binary forms, with or without
008: * modification, are permitted provided that the following conditions
009: * are met:
010: *
011: * 1. Redistributions of source code must retain the above copyright
012: * notice, this list of conditions and the following disclaimer.
013: *
014: * 2. Redistributions in binary form must reproduce the above copyright
015: * notice, this list of conditions and the following disclaimer in
016: * the documentation and/or other materials provided with the
017: * distribution.
018: *
019: * 3. The end-user documentation included with the redistribution,
020: * if any, must include the following acknowledgment:
021: * "This product includes software developed by
022: * David F. Glasser."
023: * Alternately, this acknowledgment may appear in the software itself,
024: * if and wherever such third-party acknowledgments normally appear.
025: *
026: * 4. The names "QueryForm" and "David F. Glasser" must
027: * not be used to endorse or promote products derived from this
028: * software without prior written permission. For written
029: * permission, please contact dglasser@pobox.com.
030: *
031: * 5. Products derived from this software may not be called "QueryForm",
032: * nor may "QueryForm" appear in their name, without prior written
033: * permission of David F. Glasser.
034: *
035: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
036: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
037: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
038: * DISCLAIMED. IN NO EVENT SHALL DAVID F. GLASSER, THE APACHE SOFTWARE
039: * FOUNDATION OR ITS CONTRIBUTORS, OR ANY AUTHORS OR DISTRIBUTORS
040: * OF THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
041: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
042: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
043: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
044: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
045: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
046: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
047: * SUCH DAMAGE.
048: * ====================================================================
049: *
050: * This product includes software developed by the
051: * Apache Software Foundation (http://www.apache.org/).
052: *
053: * ====================================================================
054: *
055: * $Source: /cvsroot/qform/qform/src/org/glasser/util/comparators/MethodComparator.java,v $
056: * $Revision: 1.4 $
057: * $Author: dglasser $
058: * $Date: 2005/06/06 14:56:53 $
059: *
060: * --------------------------------------------------------------------
061: */
062: package org.glasser.util.comparators;
063:
064: import java.lang.reflect.*;
065: import java.util.*;
066: import java.io.*;
067:
068: /**
069: * This Comparator is used to compare two objects of a common type, based
070: * on the value returned from a no-argument method common to both of them.
071: * (Typically, this will be a getter method.)
072: */
073: public class MethodComparator extends BaseComparator {
074:
075: private Class objectClass = null;
076:
077: private String getterName = null;
078:
079: private transient Method getter = null;
080:
081: private boolean returnTypeIsString = false;
082:
083: private boolean returnTypeIsComparable = false;
084:
085: private boolean caseSensitive = false;
086:
087: public MethodComparator(Class objectClass, String getterName) {
088: this (objectClass, getterName, false, false, null, false);
089: }
090:
091: public MethodComparator(Class objectClass, String getterName,
092: boolean nullIsGreater, boolean sortDescending,
093: Comparator nestedComparator, boolean caseSensitive) {
094: super (nullIsGreater, sortDescending, nestedComparator);
095:
096: this .caseSensitive = caseSensitive;
097: this .objectClass = objectClass;
098: this .getterName = getterName;
099:
100: try {
101: getter = objectClass.getMethod(getterName, new Class[0]);
102: } catch (NoSuchMethodException ex) {
103: throw new IllegalArgumentException("Invalid getterName: "
104: + getterName + " method not found in "
105: + objectClass);
106: }
107: Class returnTypeClass = getter.getReturnType();
108: if (returnTypeClass.equals(java.lang.String.class)) {
109: returnTypeIsString = true;
110: returnTypeIsComparable = true;
111: } else if (java.lang.Comparable.class
112: .isAssignableFrom(returnTypeClass)) {
113: returnTypeIsComparable = true;
114: }
115: }
116:
117: protected int doCompare(Object o1, Object o2) {
118:
119: try {
120: Object val1 = getter.invoke(o1, (Object[]) null);
121: Object val2 = getter.invoke(o2, (Object[]) null);
122:
123: if (val1 == null && val2 == null)
124: return 0;
125: int retVal = compareForNulls(val1, val2);
126: if (retVal != 0)
127: return retVal;
128:
129: // we know now that both val1 and val2 are non-null
130: if (returnTypeIsString) {
131: if (caseSensitive) {
132: return ((String) val1).compareTo((String) val2);
133: } else {
134: return String.CASE_INSENSITIVE_ORDER.compare(
135: (String) val1, (String) val2);
136: }
137: } else if (returnTypeIsComparable) {
138: return ((Comparable) val1).compareTo((Comparable) val2);
139: } else {
140: String s1 = val1.toString();
141: String s2 = val2.toString();
142: if (caseSensitive) {
143: return (s1).compareTo(s2);
144: } else {
145: return String.CASE_INSENSITIVE_ORDER
146: .compare(s1, s2);
147: }
148: }
149: } catch (Exception ex) {
150: throw new RuntimeException(
151: "A "
152: + ex.getClass().getName()
153: + " occurred in MethodComparator.doCompare(). objectClass="
154: + objectClass.getName() + ", getterName="
155: + getterName);
156: }
157: }
158:
159: public boolean isCaseSensitive() {
160: return caseSensitive;
161: }
162:
163: /**
164: * This must be implemented to make the MethodComparator class serializable,
165: * because the getter field (which is a Method) is not.
166: */
167: private void writeObject(java.io.ObjectOutputStream out)
168: throws IOException {
169: out.defaultWriteObject();
170: }
171:
172: /**
173: * This must be implemented to make the MethodComparator class serializable,
174: * because the getter field (which is a Method) is not.
175: */
176: private void readObject(java.io.ObjectInputStream in)
177: throws IOException, ClassNotFoundException {
178:
179: in.defaultReadObject();
180:
181: try {
182: getter = objectClass.getMethod(getterName, (Class[]) null);
183: } catch (Exception ex) {
184: throw new IOException("A " + ex.getClass().getName()
185: + " occurred in MethodComparator(): objectClass="
186: + objectClass.getName() + ", getterName="
187: + getterName);
188: }
189:
190: }
191:
192: }
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