# Interface UserDataHandler

public interface UserDataHandler
When associating an object to a key on a node using `Node.setUserData()` the application can provide a handler that gets called when the node the object is associated to is being cloned, imported, or renamed. This can be used by the application to implement various behaviors regarding the data it associates to the DOM nodes. This interface defines that handler.

See also the Document Object Model (DOM) Level 3 Core Specification.

Since:
  1.5, DOM Level 3

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final short`
  `NODE_ADOPTED`
  The node is adopted, using `Document.adoptNode()`.
  `static final short`
  `NODE_CLONED`
  The node is cloned, using `Node.cloneNode()`.
  `static final short`
  `NODE_DELETED`
  The node is deleted.
  `static final short`
  `NODE_IMPORTED`
  The node is imported, using `Document.importNode()`.
  `static final short`
  `NODE_RENAMED`
  The node is renamed, using `Document.renameNode()`.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `handle(short operation, String key, Object data, Node src, Node dst)`
  This method is called whenever the node for which this handler is registered is imported or cloned.

- ## Field Details

  - ### NODE_CLONED

    static final short NODE_CLONED
    The node is cloned, using `Node.cloneNode()`.
    See Also:
      - Constant Field Values

  - ### NODE_IMPORTED

    static final short NODE_IMPORTED
    The node is imported, using `Document.importNode()`.
    See Also:
      - Constant Field Values

  - ### NODE_DELETED

    static final short NODE_DELETED
    The node is deleted.

    Note: This may not be supported or may not be reliable in certain environments, such as Java, where the implementation has no real control over when objects are actually deleted.

    See Also:
      - Constant Field Values

  - ### NODE_RENAMED

    static final short NODE_RENAMED
    The node is renamed, using `Document.renameNode()`.
    See Also:
      - Constant Field Values

  - ### NODE_ADOPTED

    static final short NODE_ADOPTED
    The node is adopted, using `Document.adoptNode()`.
    See Also:
      - Constant Field Values

- ## Method Details

  - ### handle

    void handle(short operation, String key, Object data, Node src, Node dst)
    This method is called whenever the node for which this handler is registered is imported or cloned.
    DOM applications must not raise exceptions in a `UserDataHandler`. The effect of throwing exceptions from the handler is DOM implementation dependent.
    Parameters:
      `operation` - Specifies the type of operation that is being performed on the node.
      `key` - Specifies the key for which this handler is being called.
      `data` - Specifies the data for which this handler is being called.
      `src` - Specifies the node being cloned, adopted, imported, or renamed. This is `null` when the node is being deleted.
      `dst` - Specifies the node newly created if any, or `null`.