rdonkin 2004/05/10 12:57:58 Added: beanutils/optional/bean-collections/src/java/org/apache/commons/beanutils BeanComparator.java Log: Added new directory for bean collection components Revision Changes Path 1.1 jakarta-commons/beanutils/optional/bean-collections/src/java/org/apache/commons/beanutils/BeanComparator.java Index: BeanComparator.java =================================================================== /* * Copyright 2001-2004 The Apache Software Foundation. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.beanutils; import java.io.Serializable; import java.util.Comparator; import org.apache.commons.beanutils.PropertyUtils; import org.apache.commons.collections.comparators.ComparableComparator; /** * <p> * This comparator compares two beans by the specified bean property. * It is also possible to compare beans based on nested, indexed, * combined, mapped bean properties. Please see the [EMAIL PROTECTED] PropertyUtilsBean} * documentation for all property name possibilities. * * </p><p> * <strong>Note:</strong> The BeanComparator passes the values of the specified * bean property to a ComparableComparator, if no comparator is * specified in the constructor. If you are comparing two beans based * on a property that could contain "null" values, a suitable <code>Comparator</code> * or <code>ComparatorChain</code> should be supplied in the constructor. * </p> * * @author <a href"mailto:[EMAIL PROTECTED]">Eric Pugh</a> * @author Tim O'Brien */ public class BeanComparator implements Comparator, Serializable { private String property; private Comparator comparator; /** * <p>Constructs a Bean Comparator without a property set. * </p><p> * <strong>Note</strong> that this is intended to be used * only in bean-centric environments. * </p><p> * Until [EMAIL PROTECTED] #setProperty} is called with a non-null value. * this comparator will compare the Objects only. * </p> */ public BeanComparator() { this( null ); } /** * <p>Constructs a property-based comparator for beans. * This compares two beans by the property * specified in the property parameter. This constructor creates * a <code>BeanComparator</code> that uses a <code>ComparableComparator</code> * to compare the property values. * </p> * * <p>Passing "null" to this constructor will cause the BeanComparator * to compare objects based on natural order, that is * <code>java.lang.Comparable</code>. * </p> * * @param property String Name of a bean property, which may contain the * name of a simple, nested, indexed, mapped, or combined * property. See [EMAIL PROTECTED] PropertyUtilsBean} for property query language syntax. * If the property passed in is null then the actual objects will be compared */ public BeanComparator( String property ) { this( property, ComparableComparator.getInstance() ); } /** * Constructs a property-based comparator for beans. * This constructor creates * a BeanComparator that uses the supplied Comparator to compare * the property values. * * @param property Name of a bean property, can contain the name * of a simple, nested, indexed, mapped, or combined * property. See [EMAIL PROTECTED] PropertyUtilsBean} for property query language * syntax. * @param comparator BeanComparator will pass the values of the * specified bean property to this Comparator. * If your bean property is not a comparable or * contains null values, a suitable comparator * may be supplied in this constructor. */ public BeanComparator( String property, Comparator comparator ) { setProperty( property ); this.comparator = comparator; } /** * Sets the method to be called to compare two JavaBeans * * @param property String method name to call to compare * If the property passed in is null then the actual objects will be compared */ public void setProperty( String property ) { this.property = property; } /** * Gets the property attribute of the BeanComparator * * @return String method name to call to compare. * A null value indicates that the actual objects will be compared */ public String getProperty() { return property; } /** * Gets the Comparator being used to compare beans. */ public Comparator getComparator() { return comparator; } /** * Compare two JavaBeans by their shared property. * If [EMAIL PROTECTED] #getProperty} is null then the actual objects will be compared. * * @param o1 Object The first bean to get data from to compare against * @param o2 Object The second bean to get data from to compare * @return int negative or positive based on order */ public int compare( Object o1, Object o2 ) { if ( property == null ) { // compare the actual objects return comparator.compare( o1, o2 ); } try { Object value1 = PropertyUtils.getProperty( o1, property ); Object value2 = PropertyUtils.getProperty( o2, property ); return comparator.compare( value1, value2 ); } catch ( Exception e ) { throw new ClassCastException( e.toString() ); } } }
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