Package org.apache.velocity.tools.generic

Class SortTool

  • @DefaultKey("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:

    • Primitive type: e.g. int, char, long etc
    • Standard Object: e.g. String, Integer, Long etc
    • Object which implements the Comparable interface.

    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:
    $Id$
    Author:
    S. Brett Sutton, Nathan Bubna, Christopher Schultz

    • Constructor Detail

      • SortTool

        public SortTool()

    • Method Detail

      • sort

        public <T> Collection<T> sort​(Collection<T> c,
                              Comparator<T> comparator)
        Sorts a Collection using a Comparator. A defensive copy is made of the Collection beforehand, so the original Collection is left untouched.
        Parameters:
        c - The Collection to sort.
        comparator - The comparator to use for sorting.
        Returns:
        A copy of the original Collection, sorted using the supplied Comparator.
        Since:
        VelocityTools 2.0.1

      • sort

        public <T> T[] sort​(T[] a,
                    Comparator<T> comparator)
        Sorts an array using a Comparator. A defensive copy is made of the array beforehand, so the original array is left untouched.
        Parameters:
        a - The array to sort.
        comparator - The comparator to use for sorting.
        Returns:
        A copy of the original array, sorted using the supplied Comparator.
        Since:
        VelocityTools 2.0.1

      • sort

        public <T> Collection<T> sort​(Map<?,​T> map,
                              Comparator<T> comparator)
        Sorts a Map's values using a Comparator. A defensive copy is made of the values beforehand, so the original Map is left untouched.
        Parameters:
        map - The Map whose values should be sorted.
        comparator - The comparator to use for sorting.
        Returns:
        A copy of the original Map's values, sorted using the supplied Comparator.
        Since:
        VelocityTools 2.0.1

      • sort

        public Collection<?> sort​(Object o,
                          Comparator<?> comparator)
        Sorts a Collection (or array, or Map's values) using a Comparator. A defensive copy is made of the original beforehand, so the original is left untouched. Unsupported collection objects result in a null return value.
        Parameters:
        o - The Collection to sort.
        comparator - The comparator to use for sorting.
        Returns:
        A copy of the original Collection, sorted using the supplied Comparator.
        Since:
        VelocityTools 2.0.1

      • 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.

      • 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.