com.aragost.util
Class BeanComparator

java.lang.Object
  |
  +--com.aragost.util.BeanComparator

All Implemented Interfaces:

java.util.Comparator

public class BeanComparator

extends java.lang.Object

implements java.util.Comparator

A class to compare beans on a list of specified properties. The compare is done one property at a time until a difference is found, or all properties are equal. It is useful for sorting a collection of beans, in particular if you not always want to sort on the same properties. There is support for implementing sorting similiar to e.g. Windows Explorer where the user can click on a column header to set the sorting.

Constructor Summary

BeanComparator()
Create a new BeanComparator

BeanComparator(java.lang.String configurationString)
Create a new BeanComparator.

Method Summary

void	addFirst(java.lang.String propertyName, boolean descending) Add a new property to be used first in the comparison.
void	addLast(java.lang.String propertyName, boolean descending) Add a new property to be used last in the comparison.
void	addOrToggle(java.lang.String propertyName) Used to implement sorting similar to Windows Explorer.
int	compare(java.lang.Object a, java.lang.Object b) Compares its two arguments for order.
static int	compareObjects(java.lang.Object x, java.lang.Object y)
static int	compareObjects(java.lang.Object x, java.lang.Object y, boolean ignoreCase) A utility method to compare two objects.
boolean	isIgnoreCase() Getter for property ignoreCase.
void	remove(java.lang.String name) Remove a property to use in the comparison
void	setIgnoreCase(boolean ignoreCase) Setter for property ignoreCase.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

equals

Constructor Detail

BeanComparator

public BeanComparator()

Create a new BeanComparator

BeanComparator

public BeanComparator(java.lang.String configurationString)

Create a new BeanComparator. Configure it from the specified configuration String. The configuration string contains a comma seperated list of property names. The compare order can be set by a < or > before the name. A < means that the beans compare the same way as the property, > means that the order is reversed. E.g. "name,number" will compare the first on property name, and if the two values of name is equal the property number will be compared.

Parameters:

configurationString - The configuration String

Method Detail

compare

public int compare(java.lang.Object a,
                   java.lang.Object b)

Compares its two arguments for order. Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second. The comparison is done by comparing one property at a time, until a difference is found.The value of two properties is compared with the Comparable.compareTo() method. If the value of the property is not a Comparable it is converted to a String (which is a Comrable) with toString(). In comparisons null is considered less than anything else (and equal to null). The value of a property is read with Beans.getProperty(). If all properties compare equal then 0 is returned. A special case is when the BeanComparator has no fields added, then the comparison is forwarded to the static method compareObjects.

Specified by:

compare in interface java.util.Comparator

Parameters:

a - The first bean to compare

b - The second bean to compare

Returns:

a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second

addOrToggle

public void addOrToggle(java.lang.String propertyName)

Used to implement sorting similar to Windows Explorer. The specified property is added as the first to compare on. If the property name, match the property name of the first field, the compare order is toggled.

Parameters:

propertyName - The property name

addFirst

public void addFirst(java.lang.String propertyName,
                     boolean descending)

Add a new property to be used first in the comparison.

Parameters:

propertyName - The name of the property to sort on

descending - Indicate if the compare order on the specified property should be reversed. When used in a sorting the sorting will be descending instead of ascending.

addLast

public void addLast(java.lang.String propertyName,
                    boolean descending)

Add a new property to be used last in the comparison.

Parameters:

propertyName - The name of the property

descending - Indicate if the compare order on the specified property should be reversed. When used in a sorting the sorting will be descending instead of ascending.

compareObjects

public static int compareObjects(java.lang.Object x,
                                 java.lang.Object y)

remove

public void remove(java.lang.String name)

Remove a property to use in the comparison

Parameters:

name - The name of the property no longer to use when comparing

compareObjects

public static int compareObjects(java.lang.Object x,
                                 java.lang.Object y,
                                 boolean ignoreCase)

A utility method to compare two objects. If the arguments isn't implementing the Comparable interface then they are converted to it with the toString() method. The comparison is now done with the compareTo() method. If this method throws an exception then the class name of the two arguments are compare. This shouldn't thrown an exception since compareTo should always work for objects of the same class.

Parameters:

x -

y -

ignoreCase -

Returns:

int

isIgnoreCase

public boolean isIgnoreCase()

Getter for property ignoreCase.

Returns:

Value of property ignoreCase.

setIgnoreCase

public void setIgnoreCase(boolean ignoreCase)

Setter for property ignoreCase.

Parameters:

ignoreCase - New value of property ignoreCase.