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Spring Framework example source code file (PropertyComparator.java)

This example Spring Framework source code file (PropertyComparator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

beansexception, beanwrapperimpl, comparable, comparator, mutablesortdefinition, object, object, propertycomparator, propertycomparator, runtimeexception, sortdefinition, sortdefinition, string, string, util

The Spring Framework PropertyComparator.java source code

/*
 * Copyright 2002-2008 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.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.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
 * @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;
	}


	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 an object with null property at the end of the sort result.
		try {
			if (v1 != null) {
				result = (v2 != null ? ((Comparable) v1).compareTo(v2) : -1);
			}
			else {
				result = (v2 != null ? 1 : 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) {
		// 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 {
			this.beanWrapper.setWrappedInstance(obj);
			return this.beanWrapper.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.
	 * <p>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 {
		if (StringUtils.hasText(sortDefinition.getProperty())) {
			Collections.sort(source, new PropertyComparator(sortDefinition));
		}
	}

	/**
	 * Sort the given source according to the given sort definition.
	 * <p>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 {
		if (StringUtils.hasText(sortDefinition.getProperty())) {
			Arrays.sort(source, new PropertyComparator(sortDefinition));
		}
	}

}

Other Spring Framework examples (source code examples)

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