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 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
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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, Jean-Pierre Pawlak
Type parameters:
  • <T> – the type of objects that may be compared by this comparator
See Also:
Since:19.05.2003
/** * 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 <T> the type of objects that may be compared by this comparator * @see org.springframework.beans.BeanWrapper */
public class PropertyComparator<T> implements Comparator<T> { 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 Also:
  • MutableSortDefinition
/** * Create a new PropertyComparator for the given SortDefinition. * @see MutableSortDefinition */
public PropertyComparator(SortDefinition sortDefinition) { this.sortDefinition = sortDefinition; }
Create a PropertyComparator for the given settings.
Params:
  • property – the property to compare
  • ignoreCase – whether upper and lower case in String values should be ignored
  • ascending – whether to sort ascending (true) or descending (false)
/** * 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.
/** * 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<Object>) v1).compareTo(v2) : -1); } else { result = (v2 != null ? 1 : 0); } } catch (RuntimeException ex) { if (logger.isDebugEnabled()) { logger.debug("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.
Params:
  • obj – the object to get the property value for
Returns:the property value
/** * Get the SortDefinition's property value for the given object. * @param obj the object to get the property value for * @return the property value */
@Nullable 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.debug("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.

Params:
  • source – the input List
  • sortDefinition – the parameters to sort by
Throws:
/** * 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())) { source.sort(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.

Params:
  • source – input source
  • sortDefinition – the parameters to sort by
Throws:
/** * 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)); } } }