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/*
 * Copyright 2002-2018 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
 *
 *      https://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.Comparator;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.BeansException;
import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;

/**
 * PropertyComparator performs a comparison of two beans,
 * evaluating the specified bean property via a BeanWrapper.
 *
 * @author Juergen Hoeller
 * @author Jean-Pierre Pawlak
 * @since 19.05.2003
 * @param  the type of objects that may be compared by this comparator
 * @see org.springframework.beans.BeanWrapper
 */
public class PropertyComparator implements Comparator {

	protected final Log logger = LogFactory.getLog(getClass());

	private final SortDefinition sortDefinition;

	private final BeanWrapperImpl beanWrapper = new BeanWrapperImpl(false);


	/**
	 * Create a new PropertyComparator for the given SortDefinition.
	 * @see MutableSortDefinition
	 */
	public PropertyComparator(SortDefinition sortDefinition) {
		this.sortDefinition = sortDefinition;
	}

	/**
	 * Create a PropertyComparator for the given settings.
	 * @param property the property to compare
	 * @param ignoreCase whether upper and lower case in String values should be ignored
	 * @param ascending whether to sort ascending (true) or descending (false)
	 */
	public PropertyComparator(String property, boolean ignoreCase, boolean ascending) {
		this.sortDefinition = new MutableSortDefinition(property, ignoreCase, ascending);
	}

	/**
	 * Return the SortDefinition that this comparator uses.
	 */
	public final SortDefinition getSortDefinition() {
		return this.sortDefinition;
	}


	@Override
	@SuppressWarnings("unchecked")
	public int compare(T o1, T 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 an object with null property at the end of the sort result.
		try {
			if (v1 != null) {
				result = (v2 != null ? ((Comparable