Package org.apache.velocity.tools.generic

Class CollectionTool

  • All Implemented Interfaces:
    java.io.Serializable
    Direct Known Subclasses:
    SortTool
    @DefaultKey("collection")
public class CollectionTool
extends SafeConfig
implements java.io.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:
    Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      CollectionTool()  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected void configure​(ValueParser values)
      Does the actual configuration.
      protected static java.lang.Comparable getComparable​(java.lang.Object object, java.lang.String property)
      Safely retrieves the comparable value for the specified property from the specified object.
      java.lang.String getStringsDelimiter()
      Gets the configured strings delimiter
      boolean getStringsTrim()
      Gets whether to trim strings
      protected java.util.Collection internalSort​(java.util.List list, java.util.List properties)
      Internal sorting method.
      protected void setStringsDelimiter​(java.lang.String stringsDelimiter)
      Sets the delimiter used for separating values in a single String value.
      protected void setStringsTrim​(boolean stringsTrim)
      Sets whether strings should be trimmed when separated from a delimited string value.
      java.util.Collection sort​(java.lang.Object object)
      Sort a collection, array or map
      java.util.Collection sort​(java.lang.Object[] array)
      Sort an array
      java.util.Collection sort​(java.lang.Object[] array, java.util.List properties)
      Sorts array on several properties.
      java.util.Collection sort​(java.lang.Object object, java.lang.String property)
      Sorts the collection on a single property.
      java.util.Collection<?> sort​(java.lang.Object o, java.util.Comparator<?> comparator)
      Sorts a Collection (or array, or Map's values) using a Comparator.
      java.util.Collection sort​(java.util.Collection collection)
      Sort a collection
      <T> java.util.Collection<T> sort​(java.util.Collection<T> c, java.util.Comparator<T> comparator)
      Sorts a Collection using a Comparator.
      java.util.Collection sort​(java.util.Collection collection, java.util.List properties)
      Sorts the collection on several properties.
      java.util.Collection sort​(java.util.Map map)
      Sort map values
      <T> java.util.Collection<T> sort​(java.util.Map<?,​T> map, java.util.Comparator<T> comparator)
      Sorts a Map's values using a Comparator.
      java.util.Collection sort​(java.util.Map map, java.util.List properties)
      Sorts map values on several properties.
      <T> T[] sort​(T[] a, java.util.Comparator<T> comparator)
      Sorts an array using a Comparator.
      java.lang.String[] split​(java.lang.String value)  

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • STRINGS_DELIMITER_FORMAT_KEY

        public static final java.lang.String STRINGS_DELIMITER_FORMAT_KEY
        See Also:
        Constant Field Values

      • STRINGS_TRIM_KEY

        public static final java.lang.String STRINGS_TRIM_KEY
        See Also:
        Constant Field Values

      • DEFAULT_STRINGS_DELIMITER

        public static final java.lang.String DEFAULT_STRINGS_DELIMITER
        See Also:
        Constant Field Values

    • Constructor Detail

      • CollectionTool

        public CollectionTool()

    • Method Detail

      • setStringsDelimiter

        protected final void setStringsDelimiter​(java.lang.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:
        split(String)

      • getStringsDelimiter

        public final java.lang.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:
        split(String)

      • 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 java.lang.String[] split​(java.lang.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> java.util.Collection<T> sort​(java.util.Collection<T> c,
                                        java.util.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,
                    java.util.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> java.util.Collection<T> sort​(java.util.Map<?,​T> map,
                                        java.util.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 java.util.Collection<?> sort​(java.lang.Object o,
                                    java.util.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 java.util.Collection sort​(java.util.Collection collection)
        Sort a collection
        Parameters:
        collection - collection to sort, left unchanged
        Returns:
        new sorted collection

      • sort

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

      • sort

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

      • sort

        public java.util.Collection sort​(java.lang.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 java.util.Collection sort​(java.lang.Object object,
                                 java.lang.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 java.util.Collection sort​(java.util.Collection collection,
                                 java.util.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 java.util.Collection sort​(java.util.Map map,
                                 java.util.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 java.util.Collection sort​(java.lang.Object[] array,
                                 java.util.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 java.util.Collection internalSort​(java.util.List list,
                                            java.util.List properties)
        Internal sorting method.
        Parameters:
        list - values to sort.
        properties - the properties to sort on.
        Returns:
        new collection, sorted.

      • getComparable

        protected static java.lang.Comparable getComparable​(java.lang.Object object,
                                                    java.lang.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