001/*
002 * Copyright 2002-2012 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.beans.support;
018
019import java.util.Arrays;
020import java.util.Collections;
021import java.util.Comparator;
022import java.util.List;
023
024import org.apache.commons.logging.Log;
025import org.apache.commons.logging.LogFactory;
026
027import org.springframework.beans.BeanWrapperImpl;
028import org.springframework.beans.BeansException;
029import org.springframework.util.StringUtils;
030
031/**
032 * PropertyComparator performs a comparison of two beans,
033 * evaluating the specified bean property via a BeanWrapper.
034 *
035 * @author Juergen Hoeller
036 * @author Jean-Pierre Pawlak
037 * @since 19.05.2003
038 * @see org.springframework.beans.BeanWrapper
039 */
040public class PropertyComparator<T> implements Comparator<T> {
041
042        protected final Log logger = LogFactory.getLog(getClass());
043
044        private final SortDefinition sortDefinition;
045
046        private final BeanWrapperImpl beanWrapper = new BeanWrapperImpl(false);
047
048
049        /**
050         * Create a new PropertyComparator for the given SortDefinition.
051         * @see MutableSortDefinition
052         */
053        public PropertyComparator(SortDefinition sortDefinition) {
054                this.sortDefinition = sortDefinition;
055        }
056
057        /**
058         * Create a PropertyComparator for the given settings.
059         * @param property the property to compare
060         * @param ignoreCase whether upper and lower case in String values should be ignored
061         * @param ascending whether to sort ascending (true) or descending (false)
062         */
063        public PropertyComparator(String property, boolean ignoreCase, boolean ascending) {
064                this.sortDefinition = new MutableSortDefinition(property, ignoreCase, ascending);
065        }
066
067        /**
068         * Return the SortDefinition that this comparator uses.
069         */
070        public final SortDefinition getSortDefinition() {
071                return this.sortDefinition;
072        }
073
074
075        @Override
076        @SuppressWarnings("unchecked")
077        public int compare(T o1, T o2) {
078                Object v1 = getPropertyValue(o1);
079                Object v2 = getPropertyValue(o2);
080                if (this.sortDefinition.isIgnoreCase() && (v1 instanceof String) && (v2 instanceof String)) {
081                        v1 = ((String) v1).toLowerCase();
082                        v2 = ((String) v2).toLowerCase();
083                }
084
085                int result;
086
087                // Put an object with null property at the end of the sort result.
088                try {
089                        if (v1 != null) {
090                                result = (v2 != null ? ((Comparable<Object>) v1).compareTo(v2) : -1);
091                        }
092                        else {
093                                result = (v2 != null ? 1 : 0);
094                        }
095                }
096                catch (RuntimeException ex) {
097                        if (logger.isWarnEnabled()) {
098                                logger.warn("Could not sort objects [" + o1 + "] and [" + o2 + "]", ex);
099                        }
100                        return 0;
101                }
102
103                return (this.sortDefinition.isAscending() ? result : -result);
104        }
105
106        /**
107         * Get the SortDefinition's property value for the given object.
108         * @param obj the object to get the property value for
109         * @return the property value
110         */
111        private Object getPropertyValue(Object obj) {
112                // If a nested property cannot be read, simply return null
113                // (similar to JSTL EL). If the property doesn't exist in the
114                // first place, let the exception through.
115                try {
116                        this.beanWrapper.setWrappedInstance(obj);
117                        return this.beanWrapper.getPropertyValue(this.sortDefinition.getProperty());
118                }
119                catch (BeansException ex) {
120                        logger.info("PropertyComparator could not access property - treating as null for sorting", ex);
121                        return null;
122                }
123        }
124
125
126        /**
127         * Sort the given List according to the given sort definition.
128         * <p>Note: Contained objects have to provide the given property
129         * in the form of a bean property, i.e. a getXXX method.
130         * @param source the input List
131         * @param sortDefinition the parameters to sort by
132         * @throws java.lang.IllegalArgumentException in case of a missing propertyName
133         */
134        public static void sort(List<?> source, SortDefinition sortDefinition) throws BeansException {
135                if (StringUtils.hasText(sortDefinition.getProperty())) {
136                        Collections.sort(source, new PropertyComparator<Object>(sortDefinition));
137                }
138        }
139
140        /**
141         * Sort the given source according to the given sort definition.
142         * <p>Note: Contained objects have to provide the given property
143         * in the form of a bean property, i.e. a getXXX method.
144         * @param source input source
145         * @param sortDefinition the parameters to sort by
146         * @throws java.lang.IllegalArgumentException in case of a missing propertyName
147         */
148        public static void sort(Object[] source, SortDefinition sortDefinition) throws BeansException {
149                if (StringUtils.hasText(sortDefinition.getProperty())) {
150                        Arrays.sort(source, new PropertyComparator<Object>(sortDefinition));
151                }
152        }
153
154}