org.springframework.beans.support.PropertyComparator Maven / Gradle / Ivy
/*
* Copyright 2002-2005 the original author or authors.
*
* 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.springframework.beans.support;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.BeansException;
/**
* PropertyComparator performs a comparison of two beans,
* using the specified bean property via a BeanWrapper.
*
* @author Juergen Hoeller
* @author Jean-Pierre Pawlak
* @since 19.05.2003
*/
public class PropertyComparator implements Comparator {
protected final Log logger = LogFactory.getLog(getClass());
private final SortDefinition sortDefinition;
private final Map cachedBeanWrappers = new HashMap();
public PropertyComparator(SortDefinition sortDefinition) {
this.sortDefinition = sortDefinition;
}
public int compare(Object o1, Object o2) {
Object v1 = getPropertyValue(o1);
Object v2 = getPropertyValue(o2);
if (this.sortDefinition.isIgnoreCase() && (v1 instanceof String) && (v2 instanceof String)) {
v1 = ((String) v1).toLowerCase();
v2 = ((String) v2).toLowerCase();
}
int result;
// Put a null property at the end of the sort.
try {
if (v1 != null) {
if (v2 != null) {
result = ((Comparable) v1).compareTo(v2);
}
else {
result = -1;
}
}
else {
if (v2 != null) {
result = 1;
}
else {
result = 0;
}
}
}
catch (RuntimeException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Could not sort objects [" + o1 + "] and [" + o2 + "]", ex);
}
return 0;
}
return (this.sortDefinition.isAscending() ? result : -result);
}
/**
* Get the SortDefinition's property value for the given object.
* @param obj the object to get the property value for
* @return the property value
*/
private Object getPropertyValue(Object obj) {
BeanWrapper bw = (BeanWrapper) this.cachedBeanWrappers.get(obj);
if (bw == null) {
bw = new BeanWrapperImpl(obj);
this.cachedBeanWrappers.put(obj, bw);
}
// If a nested property cannot be read, simply return null
// (similar to JSTL EL). If the property doesn't exist in the
// first place, let the exception through.
try {
return bw.getPropertyValue(this.sortDefinition.getProperty());
}
catch (BeansException ex) {
logger.info("PropertyComparator could not access property - treating as null for sorting", ex);
return null;
}
}
/**
* Sort the given List according to the given sort definition.
* Note: Contained objects have to provide the given property
* in the form of a bean property, i.e. a getXXX method.
* @param source the input List
* @param sortDefinition the parameters to sort by
* @throws java.lang.IllegalArgumentException in case of a missing propertyName
*/
public static void sort(List source, SortDefinition sortDefinition) throws BeansException {
Collections.sort(source, new PropertyComparator(sortDefinition));
}
/**
* Sort the given source according to the given sort definition.
*
Note: Contained objects have to provide the given property
* in the form of a bean property, i.e. a getXXX method.
* @param source input source
* @param sortDefinition the parameters to sort by
* @throws java.lang.IllegalArgumentException in case of a missing propertyName
*/
public static void sort(Object[] source, SortDefinition sortDefinition) throws BeansException {
Arrays.sort(source, new PropertyComparator(sortDefinition));
}
}