org.springframework.beans.propertyeditors

## Class CustomCollectionEditor

- java.lang.Object
- - java.beans.PropertyEditorSupport
  - - org.springframework.beans.propertyeditors.CustomCollectionEditor

- All Implemented Interfaces:
    PropertyEditor

      public class CustomCollectionEditor
      extends PropertyEditorSupport

  Property editor for Collections, converting any source Collection to a given target Collection type.

  By default registered for Set, SortedSet and List, to automatically convert any given Collection to one of those target types if the type does not match the target property.

  Since:
    1.1.3
  Author:
    Juergen Hoeller
  See Also:
    `Collection`, `Set`, `SortedSet`, `List`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `CustomCollectionEditor(Class collectionType)` Create a new CustomCollectionEditor for the given target type, keeping an incoming `null` as-is.
    `CustomCollectionEditor(Class collectionType, boolean nullAsEmptyCollection)` Create a new CustomCollectionEditor for the given target type.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected boolean` | `alwaysCreateNewCollection()` Return whether to always create a new Collection, even if the type of the passed-in Collection already matches.
    `protected Object` | `convertElement(Object element)` Hook to convert each encountered Collection/array element.
    `protected Collection` | `createCollection(Class collectionType, int initialCapacity)` Create a Collection of the given type, with the given initial capacity (if supported by the Collection type).
    `String` | `getAsText()` This implementation returns `null` to indicate that there is no appropriate text representation.
    `void` | `setAsText(String text)` Convert the given text value to a Collection with a single element.
    `void` | `setValue(Object value)` Convert the given value to a Collection of the target type.

    - ### Methods inherited from class java.beans.PropertyEditorSupport

      `addPropertyChangeListener, firePropertyChange, getCustomEditor, getJavaInitializationString, getSource, getTags, getValue, isPaintable, paintValue, removePropertyChangeListener, setSource, supportsCustomEditor`

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### CustomCollectionEditor

          public CustomCollectionEditor(Class collectionType)

      Create a new CustomCollectionEditor for the given target type, keeping an incoming `null` as-is.
      Parameters:
        `collectionType` - the target type, which needs to be a sub-interface of Collection or a concrete Collection class
      See Also:
        `Collection`, `ArrayList`, `TreeSet`, `LinkedHashSet`

    - #### CustomCollectionEditor

          public CustomCollectionEditor(Class collectionType,
                                boolean nullAsEmptyCollection)

      Create a new CustomCollectionEditor for the given target type.

      If the incoming value is of the given type, it will be used as-is. If it is a different Collection type or an array, it will be converted to a default implementation of the given Collection type. If the value is anything else, a target Collection with that single value will be created.

      The default Collection implementations are: ArrayList for List, TreeSet for SortedSet, and LinkedHashSet for Set.

      Parameters:
        `collectionType` - the target type, which needs to be a sub-interface of Collection or a concrete Collection class
        `nullAsEmptyCollection` - whether to convert an incoming `null` value to an empty Collection (of the appropriate type)
      See Also:
        `Collection`, `ArrayList`, `TreeSet`, `LinkedHashSet`

  - ### Method Detail

    - #### setAsText

          public void setAsText(String text)
                         throws IllegalArgumentException

      Convert the given text value to a Collection with a single element.
      Specified by:
        `setAsText` in interface `PropertyEditor`
      Overrides:
        `setAsText` in class `PropertyEditorSupport`
      Throws:
        `IllegalArgumentException`

    - #### setValue

          public void setValue(Object value)

      Convert the given value to a Collection of the target type.
      Specified by:
        `setValue` in interface `PropertyEditor`
      Overrides:
        `setValue` in class `PropertyEditorSupport`

    - #### createCollection

          protected Collection createCollection(Class collectionType,
                                    int initialCapacity)

      Create a Collection of the given type, with the given initial capacity (if supported by the Collection type).
      Parameters:
        `collectionType` - a sub-interface of Collection
        `initialCapacity` - the initial capacity
      Returns:
        the new Collection instance

    - #### alwaysCreateNewCollection

          protected boolean alwaysCreateNewCollection()

      Return whether to always create a new Collection, even if the type of the passed-in Collection already matches.

      Default is "false"; can be overridden to enforce creation of a new Collection, for example to convert elements in any case.

      See Also:
        `convertElement(java.lang.Object)`

    - #### convertElement

          protected Object convertElement(Object element)

      Hook to convert each encountered Collection/array element. The default implementation simply returns the passed-in element as-is.

      Can be overridden to perform conversion of certain elements, for example String to Integer if a String array comes in and should be converted to a Set of Integer objects.

      Only called if actually creating a new Collection! This is by default not the case if the type of the passed-in Collection already matches. Override `alwaysCreateNewCollection()` to enforce creating a new Collection in every case.

      Parameters:
        `element` - the source element
      Returns:
        the element to be used in the target Collection
      See Also:
        `alwaysCreateNewCollection()`

    - #### getAsText

          public String getAsText()

      This implementation returns `null` to indicate that there is no appropriate text representation.
      Specified by:
        `getAsText` in interface `PropertyEditor`
      Overrides:
        `getAsText` in class `PropertyEditorSupport`