org.apache.commons.beanutils

Class BeanComparator<T>

java.lang.Object

org.apache.commons.beanutils.BeanComparator<T>

Type Parameters:

T - the type of beans to be compared by this Comparator

All Implemented Interfaces:

Serializable, Comparator<T>

public class BeanComparator<T>
extends Object
implements Comparator<T>, Serializable

This comparator compares two beans by the specified bean property. It is also possible to compare beans based on nested, indexed, combined, mapped bean properties. Please see the PropertyUtilsBean documentation for all property name possibilities.

Note: The BeanComparator passes the values of the specified bean property to a ComparableComparator, if no comparator is specified in the constructor. If you are comparing two beans based on a property that could contain "null" values, a suitable Comparator or ComparatorChain should be supplied in the constructor. Note that the passed in Comparator must be able to handle the passed in objects. Because the type of the property to be compared is not known at compile time no type checks can be performed by the compiler. Thus ClassCastException exceptions can be thrown if unexpected property values occur.

Version:

$Id$

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
BeanComparator() Constructs a Bean Comparator without a property set.
BeanComparator(String property) Constructs a property-based comparator for beans.
BeanComparator(String property, Comparator<?> comparator) Constructs a property-based comparator for beans.

Method Summary

Modifier and Type	Method and Description
int	compare(T o1, T o2) Compare two JavaBeans by their shared property.
boolean	equals(Object o) Two BeanComparator's are equals if and only if the wrapped comparators and the property names to be compared are equal.
Comparator<?>	getComparator() Gets the Comparator being used to compare beans.
String	getProperty() Gets the property attribute of the BeanComparator
int	hashCode() Hashcode compatible with equals.
void	setProperty(String property) Sets the method to be called to compare two JavaBeans

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Constructor Detail

BeanComparator

public BeanComparator()

Constructs a Bean Comparator without a property set.

Note that this is intended to be used only in bean-centric environments.

Until setProperty(java.lang.String) is called with a non-null value. this comparator will compare the Objects only.

BeanComparator

public BeanComparator(String property)

Constructs a property-based comparator for beans. This compares two beans by the property specified in the property parameter. This constructor creates a BeanComparator that uses a ComparableComparator to compare the property values.

Passing "null" to this constructor will cause the BeanComparator to compare objects based on natural order, that is java.lang.Comparable.

Parameters:

property - String Name of a bean property, which may contain the name of a simple, nested, indexed, mapped, or combined property. See PropertyUtilsBean for property query language syntax. If the property passed in is null then the actual objects will be compared

BeanComparator

public BeanComparator(String property,
                      Comparator<?> comparator)

Constructs a property-based comparator for beans. This constructor creates a BeanComparator that uses the supplied Comparator to compare the property values.

Parameters:

property - Name of a bean property, can contain the name of a simple, nested, indexed, mapped, or combined property. See PropertyUtilsBean for property query language syntax.

comparator - BeanComparator will pass the values of the specified bean property to this Comparator. If your bean property is not a comparable or contains null values, a suitable comparator may be supplied in this constructor.

Method Detail

setProperty

public void setProperty(String property)

Sets the method to be called to compare two JavaBeans

Parameters:

property - String method name to call to compare If the property passed in is null then the actual objects will be compared

getProperty

public String getProperty()

Gets the property attribute of the BeanComparator

Returns:

String method name to call to compare. A null value indicates that the actual objects will be compared

getComparator

public Comparator<?> getComparator()

Gets the Comparator being used to compare beans.

Returns:

the Comparator being used to compare beans

compare

public int compare(T o1,
                   T o2)

Compare two JavaBeans by their shared property. If getProperty() is null then the actual objects will be compared.

Specified by:

compare in interface Comparator<T>

Parameters:

o1 - Object The first bean to get data from to compare against

o2 - Object The second bean to get data from to compare

Returns:

int negative or positive based on order

equals

public boolean equals(Object o)

Two BeanComparator's are equals if and only if the wrapped comparators and the property names to be compared are equal.

Specified by:

equals in interface Comparator<T>

Overrides:

equals in class Object

Parameters:

o - Comparator to compare to

Returns:

whether the the comparators are equal or not

hashCode

public int hashCode()

Hashcode compatible with equals.

Overrides:

hashCode in class Object

Returns:

the hash code for this comparator