Class CollectionTool

java.lang.Object
org.apache.velocity.tools.generic.SafeConfig
org.apache.velocity.tools.generic.CollectionTool
All Implemented Interfaces:
Serializable
Direct Known Subclasses:
SortTool
@DefaultKey("collection") public class CollectionTool extends SafeConfig implements Serializable

CollectionTool allows a user to sort a collection (or array, iterator, etc) on any arbitrary set of properties exposed by the objects contained within the collection, and to generate arrays by splitting strings.

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

The sort methods 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 3.0
Version:
$Id$
Author:
S. Brett Sutton, Nathan Bubna
See Also:

  • Field Details

  • Constructor Details

    • CollectionTool

      public CollectionTool()

  • Method Details

    • setStringsDelimiter

      protected final void setStringsDelimiter(String stringsDelimiter)
      Sets the delimiter used for separating values in a single String value. The default string delimiter is a comma.
      Parameters:
      stringsDelimiter - strings delimiter
      See Also:

    • getStringsDelimiter

      public final String getStringsDelimiter()
      Gets the configured strings delimiter
      Returns:
      strings delimiter

    • setStringsTrim

      protected final void setStringsTrim(boolean stringsTrim)
      Sets whether strings should be trimmed when separated from a delimited string value. The default is true.
      Parameters:
      stringsTrim - flag value
      See Also:

    • getStringsTrim

      public final boolean getStringsTrim()
      Gets whether to trim strings
      Returns:
      whether to trim strings

    • configure

      protected void configure(ValueParser values)
      Does the actual configuration. This is protected, so subclasses may share the same ValueParser and call configure at any time, while preventing templates from doing so when configure(Map) is locked.
      Overrides:
      configure in class SafeConfig
      Parameters:
      values - configuration values

    • split

      public String[] split(String value)
      Parameters:
      value - the value to be converted
      Returns:
      an array of String objects containing all of the values derived from the specified array, Collection, or delimited String

    • 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 and null elements filtered out.
      Type Parameters:
      T - collection content class
      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 and null elements filtered out.
      Type Parameters:
      T - array content class
      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.
      Type Parameters:
      T - Map values class
      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(Collection collection)
      Sort a collection
      Parameters:
      collection - collection to sort, left unchanged
      Returns:
      new sorted collection

    • sort

      public Collection sort(Object[] array)
      Sort an array
      Parameters:
      array - array to sort, left unchanged
      Returns:
      new sorted collection

    • sort

      public Collection sort(Map map)
      Sort map values
      Parameters:
      map - map to sort
      Returns:
      new sorted collection of map values

    • sort

      public Collection sort(Object object)
      Sort a collection, array or map
      Parameters:
      object - collection, array or map to sort
      Returns:
      new sorted collection, or null of object type is not supported

    • sort

      public Collection sort(Object object, String property)
      Sorts the collection on a single property.
      Parameters:
      object - the collection to be sorted, left unchanged.
      property - the property to sort on.
      Returns:
      new collection, sorted.

    • sort

      public Collection sort(Collection collection, List properties)
      Sorts the collection on several properties.
      Parameters:
      collection - the collection to be sorted, left unchanged.
      properties - the properties to sort on.
      Returns:
      new collection, sorted.

    • sort

      public Collection sort(Map map, List properties)
      Sorts map values on several properties.
      Parameters:
      map - the map to be sorted, left unchanged.
      properties - the properties to sort on.
      Returns:
      new collection, sorted.

    • sort

      public Collection sort(Object[] array, List properties)
      Sorts array on several properties.
      Parameters:
      array - array to be sorted, left unchanged.
      properties - the properties to sort on.
      Returns:
      new collection, sorted.

    • internalSort

      protected Collection internalSort(List list, List properties)
      Internal sorting method.
      Parameters:
      list - values to sort.
      properties - the properties to sort on.
      Returns:
      new collection, sorted.

    • 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.
      Parameters:
      object - target object
      property - target property
      Returns:
      comparable