org.apache.velocity.tools.generic
Class SortTool

java.lang.Object
  extended by org.apache.velocity.tools.generic.SortTool

@DefaultKey(value="sorter")
public class SortTool
extends Object

SortTool allows a user to sort a collection (or array, iterator, etc) on any arbitary set of properties exposed by the objects contained within the collection.

The sort tool is specifically designed to use within a #foreach but you may find other uses for it.

The sort tool can handle all of the collection types supported by #foreach and the same constraints apply as well as the following. Every object in the collection must support the set of properties selected to sort on. Each property which is to be sorted on must return one of the follow:

During the sort operation all properties are compared by calling compareTo() with the exception of Strings for which compareToIgnoreCase() is called.

The sort is performed by calling Collections.sort() after marshalling the collection to sort into an appropriate collection type. The original collection will not be re-ordered; a new list containing the sorted elements will always be returned.

The tool is used as follows:

 Single Property Sort
 #foreach($obj in $sorter.sort($objects, "name"))
   $obj.name Ordinal= $obj.ordinal
 #end
 End

 Multiple Property Sort
 #foreach($obj in $sorter.sort($objects, ["name", "ordinal"]))
   $obj.name, $obj.ordinal
 #end
 End
 
The sort method takes two parameters a collection and a property name or an array of property names. The property names and corresponding methods must conform to java bean standards since commons-beanutils is used to extract the property values.

By default the sort tool sorts ascending, you can override this by adding a sort type suffix to any property name.

The supported suffixes are:

 For ascending
 :asc
 For descending
 :desc

 Example
 #foreach($obj in $sorter.sort($objects, ["name:asc", "ordinal:desc"]))
   $obj.name, $obj.ordinal
 #end
 

This will sort first by Name in ascending order and then by Ordinal in descending order, of course you could have left the :asc off of the 'Name' property as ascending is always the default.

 Example tools.xml config (if you want to use this with VelocityView):
 <tools>
   <toolbox scope="application">
     <tool class="org.apache.velocity.tools.generic.SortTool"/>
   </toolbox>
 </tools>
 

Since:
VelocityTools 1.2
Version:
$Id: SortTool.java 564672 2007-08-10 16:50:04Z nbubna $
Author:
S. Brett Sutton, Nathan Bubna

Nested Class Summary
static class SortTool.PropertiesComparator
          Does all of the comparisons
 
Constructor Summary
SortTool()
           
 
Method Summary
protected static Comparable getComparable(Object object, String property)
          Safely retrieves the comparable value for the specified property from the specified object.
protected  Collection internalSort(List list, List properties)
           
 Collection sort(Collection collection)
           
 Collection sort(Collection collection, List properties)
           
 Collection sort(Map map)
           
 Collection sort(Map map, List properties)
           
 Collection sort(Object[] array)
           
 Collection sort(Object[] array, List properties)
           
 Collection sort(Object object, String property)
          Sorts the collection on a single property.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

SortTool

public SortTool()
Method Detail

sort

public Collection sort(Collection collection)

sort

public Collection sort(Object[] array)

sort

public Collection sort(Map map)

sort

public Collection sort(Object object,
                       String property)
Sorts the collection on a single property.

Parameters:
object - the collection to be sorted.
property - the property to sort on.

sort

public Collection sort(Collection collection,
                       List properties)

sort

public Collection sort(Map map,
                       List properties)

sort

public Collection sort(Object[] array,
                       List properties)

internalSort

protected Collection internalSort(List list,
                                  List properties)

getComparable

protected static Comparable getComparable(Object object,
                                          String property)
Safely retrieves the comparable value for the specified property from the specified object. Subclasses that wish to perform more advanced, efficient, or just different property retrieval methods should override this method to do so.



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