Package org.apache.xerces.dom

Class AttrImpl

java.lang.Object
org.apache.xerces.dom.NodeImpl
org.apache.xerces.dom.AttrImpl
All Implemented Interfaces:
Serializable, Cloneable, Attr, EventTarget, Node, NodeList, TypeInfo
Direct Known Subclasses:
AttrNSImpl, DeferredAttrImpl
public class AttrImpl extends NodeImpl implements Attr, TypeInfo
Attribute represents an XML-style attribute of an Element. Typically, the allowable values are controlled by its declaration in the Document Type Definition (DTD) governing this kind of document.

If the attribute has not been explicitly assigned a value, but has been declared in the DTD, it will exist and have that default. Only if neither the document nor the DTD specifies a value will the Attribute really be considered absent and have no value; in that case, querying the attribute will return null.

Attributes may have multiple children that contain their data. (XML allows attributes to contain entity references, and tokenized attribute types such as NMTOKENS may have a child for each token.) For convenience, the Attribute object's getValue() method returns the string version of the attribute's value.

Attributes are not children of the Elements they belong to, in the usual sense, and have no valid Parent reference. However, the spec says they _do_ belong to a specific Element, and an INUSE exception is to be thrown if the user attempts to explicitly share them between elements.

Note that Elements do not permit attributes to appear to be shared (see the INUSE exception), so this object's mutability is officially not an issue.

Note: The ownerNode attribute is used to store the Element the Attr node is associated with. Attr nodes do not have parent nodes. Besides, the getOwnerElement() method can be used to get the element node this attribute is associated with.

AttrImpl does not support Namespaces. AttrNSImpl, which inherits from it, does.

AttrImpl used to inherit from ParentNode. It now directly inherits from NodeImpl and provide its own implementation of the ParentNode's behavior. The reason is that we now try and avoid to always create a Text node to hold the value of an attribute. The DOM spec requires it, so we still have to do it in case getFirstChild() is called for instance. The reason attribute values are stored as a list of nodes is so that they can carry more than a simple string. They can also contain EntityReference nodes. However, most of the times people only have a single string that they only set and get through Element.set/getAttribute or Attr.set/getValue. In this new version, the Attr node has a value pointer which can either be the String directly or a pointer to the first ChildNode. A flag tells which one it currently is. Note that while we try to stick with the direct String as much as possible once we've switched to a node there is no going back. This is because we have no way to know whether the application keeps referring to the node we once returned.

The gain in memory varies on the density of attributes in the document. But in the tests I've run I've seen up to 12% of memory gain. And the good thing is that it also leads to a slight gain in speed because we allocate fewer objects! I mean, that's until we have to actually create the node...

To avoid too much duplicated code, I got rid of ParentNode and renamed ChildAndParentNode, which I never really liked, to ParentNode for simplicity, this doesn't make much of a difference in memory usage because there are only very few objects that are only a Parent. This is only true now because AttrImpl now inherits directly from NodeImpl and has its own implementation of the ParentNode's node behavior. So there is still some duplicated code there.

This class doesn't directly support mutation events, however, it notifies the document when mutations are performed so that the document class do so.

WARNING: Some of the code here is partially duplicated in ParentNode, be careful to keep these two classes in sync!

INTERNAL:

Usage of this class is not supported. It may be altered or removed at any time.
Since:
PR-DOM-Level-1-19980818.
Version:
$Id: AttrImpl.java 924245 2010-03-17 11:58:14Z mrglavas $
Author:
Arnaud Le Hors, IBM, Joe Kesselman, IBM, Andy Clark, IBM
See Also:

  • Field Details

    • value

      protected Object value
      This can either be a String or the first child node.

    • name

      protected String name
      Attribute name.

  • Constructor Details

    • AttrImpl

      protected AttrImpl(CoreDocumentImpl ownerDocument, String name)
      Attribute has no public constructor. Please use the factory method in the Document class.

    • AttrImpl

      protected AttrImpl()

  • Method Details

    • makeChildNode

      protected void makeChildNode()

    • setOwnerDocument

      protected void setOwnerDocument(CoreDocumentImpl doc)
      NON-DOM set the ownerDocument of this node and its children
      Overrides:
      setOwnerDocument in class NodeImpl

    • setIdAttribute

      public void setIdAttribute(boolean id)
      NON-DOM: set the type of this attribute to be ID type.
      Parameters:
      id -

    • isId

      public boolean isId()
      DOM Level 3: isId
      Specified by:
      isId in interface Attr

    • cloneNode

      public Node cloneNode(boolean deep)
      Description copied from class: NodeImpl
      Returns a duplicate of a given node. You can consider this a generic "copy constructor" for nodes. The newly returned object should be completely independent of the source object's subtree, so changes in one after the clone has been made will not affect the other.

      Note: since we never have any children deep is meaningless here, ParentNode overrides this behavior.

      Specified by:
      cloneNode in interface Node
      Overrides:
      cloneNode in class NodeImpl
      See Also:

    • getNodeType

      public short getNodeType()
      A short integer indicating what type of node this is. The named constants for this value are defined in the org.w3c.dom.Node interface.
      Specified by:
      getNodeType in interface Node
      Specified by:
      getNodeType in class NodeImpl

    • getNodeName

      public String getNodeName()
      Returns the attribute name
      Specified by:
      getNodeName in interface Node
      Specified by:
      getNodeName in class NodeImpl

    • setNodeValue

      public void setNodeValue(String value) throws DOMException
      Implicit in the rerouting of getNodeValue to getValue is the need to redefine setNodeValue, for symmetry's sake. Note that since we're explicitly providing a value, Specified should be set true.... even if that value equals the default.
      Specified by:
      setNodeValue in interface Node
      Overrides:
      setNodeValue in class NodeImpl
      Throws:
      DOMException

    • getTypeName

      public String getTypeName()
      Specified by:
      getTypeName in interface TypeInfo
      See Also:

    • getTypeNamespace

      public String getTypeNamespace()
      Specified by:
      getTypeNamespace in interface TypeInfo
      See Also:

    • getSchemaTypeInfo

      public TypeInfo getSchemaTypeInfo()
      Method getSchemaTypeInfo.
      Specified by:
      getSchemaTypeInfo in interface Attr
      Returns:
      TypeInfo

    • getNodeValue

      public String getNodeValue()
      In Attribute objects, NodeValue is considered a synonym for Value.
      Specified by:
      getNodeValue in interface Node
      Overrides:
      getNodeValue in class NodeImpl
      See Also:

    • getName

      public String getName()
      In Attributes, NodeName is considered a synonym for the attribute's Name
      Specified by:
      getName in interface Attr

    • setValue

      public void setValue(String newvalue)
      The DOM doesn't clearly define what setValue(null) means. I've taken it as "remove all children", which from outside should appear similar to setting it to the empty string.
      Specified by:
      setValue in interface Attr

    • getValue

      public String getValue()
      The "string value" of an Attribute is its text representation, which in turn is a concatenation of the string values of its children.
      Specified by:
      getValue in interface Attr

    • getSpecified

      public boolean getSpecified()
      The "specified" flag is true if and only if this attribute's value was explicitly specified in the original document. Note that the implementation, not the user, is in charge of this property. If the user asserts an Attribute value (even if it ends up having the same value as the default), it is considered a specified attribute. If you really want to revert to the default, delete the attribute from the Element, and the Implementation will re-assert the default (if any) in its place, with the appropriate specified=false setting.
      Specified by:
      getSpecified in interface Attr

    • getElement

      public Element getElement()
      Deprecated.
      Previous working draft of DOM Level 2. New method is getOwnerElement().
      Returns the element node that this attribute is associated with, or null if the attribute has not been added to an element.
      See Also:

    • getOwnerElement

      public Element getOwnerElement()
      Returns the element node that this attribute is associated with, or null if the attribute has not been added to an element.
      Specified by:
      getOwnerElement in interface Attr
      Since:
      WD-DOM-Level-2-19990719

    • normalize

      public void normalize()
      Description copied from class: NodeImpl
      Puts all Text nodes in the full depth of the sub-tree underneath this Node, including attribute nodes, into a "normal" form where only markup (e.g., tags, comments, processing instructions, CDATA sections, and entity references) separates Text nodes, i.e., there are no adjacent Text nodes. This can be used to ensure that the DOM view of a document is the same as if it were saved and re-loaded, and is useful when operations (such as XPointer lookups) that depend on a particular document tree structure are to be used.In cases where the document contains CDATASections, the normalize operation alone may not be sufficient, since XPointers do not differentiate between Text nodes and CDATASection nodes.

      Note that this implementation simply calls normalize() on this Node's children. It is up to implementors or Node to override normalize() to take action.

      Specified by:
      normalize in interface Node
      Overrides:
      normalize in class NodeImpl

    • setSpecified

      public void setSpecified(boolean arg)
      NON-DOM, for use by parser

    • setType

      public void setType(Object type)
      NON-DOM: used by the parser
      Parameters:
      type -

    • toString

      public String toString()
      NON-DOM method for debugging convenience
      Overrides:
      toString in class NodeImpl

    • hasChildNodes

      public boolean hasChildNodes()
      Test whether this node has any children. Convenience shorthand for (Node.getFirstChild()!=null)
      Specified by:
      hasChildNodes in interface Node
      Overrides:
      hasChildNodes in class NodeImpl
      See Also:

    • getChildNodes

      public NodeList getChildNodes()
      Obtain a NodeList enumerating all children of this node. If there are none, an (initially) empty NodeList is returned.

      NodeLists are "live"; as children are added/removed the NodeList will immediately reflect those changes. Also, the NodeList refers to the actual nodes, so changes to those nodes made via the DOM tree will be reflected in the NodeList and vice versa.

      In this implementation, Nodes implement the NodeList interface and provide their own getChildNodes() support. Other DOMs may solve this differently.

      Specified by:
      getChildNodes in interface Node
      Overrides:
      getChildNodes in class NodeImpl

    • getFirstChild

      public Node getFirstChild()
      The first child of this Node, or null if none.
      Specified by:
      getFirstChild in interface Node
      Overrides:
      getFirstChild in class NodeImpl
      See Also:

    • getLastChild

      public Node getLastChild()
      The last child of this Node, or null if none.
      Specified by:
      getLastChild in interface Node
      Overrides:
      getLastChild in class NodeImpl
      See Also:

    • insertBefore

      public Node insertBefore(Node newChild, Node refChild) throws DOMException
      Move one or more node(s) to our list of children. Note that this implicitly removes them from their previous parent.
      Specified by:
      insertBefore in interface Node
      Overrides:
      insertBefore in class NodeImpl
      Parameters:
      newChild - The Node to be moved to our subtree. As a convenience feature, inserting a DocumentNode will instead insert all its children.
      refChild - Current child which newChild should be placed immediately before. If refChild is null, the insertion occurs after all existing Nodes, like appendChild().
      Returns:
      newChild, in its new state (relocated, or emptied in the case of DocumentNode.)
      Throws:
      DOMException
      See Also:

    • removeChild

      public Node removeChild(Node oldChild) throws DOMException
      Remove a child from this Node. The removed child's subtree remains intact so it may be re-inserted elsewhere.
      Specified by:
      removeChild in interface Node
      Overrides:
      removeChild in class NodeImpl
      Returns:
      oldChild, in its new state (removed).
      Throws:
      DOMException
      See Also:

    • replaceChild

      public Node replaceChild(Node newChild, Node oldChild) throws DOMException
      Make newChild occupy the location that oldChild used to have. Note that newChild will first be removed from its previous parent, if any. Equivalent to inserting newChild before oldChild, then removing oldChild.
      Specified by:
      replaceChild in interface Node
      Overrides:
      replaceChild in class NodeImpl
      Returns:
      oldChild, in its new state (removed).
      Throws:
      DOMException
      See Also:

    • getLength

      public int getLength()
      NodeList method: Count the immediate children of this node
      Specified by:
      getLength in interface NodeList
      Overrides:
      getLength in class NodeImpl
      Returns:
      int
      See Also:

    • item

      public Node item(int index)
      NodeList method: Return the Nth immediate child of this node, or null if the index is out of bounds.
      Specified by:
      item in interface NodeList
      Overrides:
      item in class NodeImpl
      Parameters:
      index - int
      Returns:
      org.w3c.dom.Node
      See Also:

    • isEqualNode

      public boolean isEqualNode(Node arg)
      DOM Level 3 WD- Experimental. Override inherited behavior from ParentNode to support deep equal. isEqualNode is always deep on Attr nodes.
      Specified by:
      isEqualNode in interface Node
      Overrides:
      isEqualNode in class NodeImpl
      Parameters:
      arg - The node to compare equality with.
      Returns:
      If the nodes, and possibly subtrees are equal, true otherwise false.

    • isDerivedFrom

      public boolean isDerivedFrom(String typeNamespaceArg, String typeNameArg, int derivationMethod)
      Introduced in DOM Level 3.

      Checks if a type is derived from another by restriction. See: http://www.w3.org/TR/DOM-Level-3-Core/core.html#TypeInfo-isDerivedFrom

      Specified by:
      isDerivedFrom in interface TypeInfo
      Parameters:
      typeNamespaceArg - The namspace of the ancestor type declaration
      typeNameArg - The name of the ancestor type declaration
      derivationMethod - The derivation method
      Returns:
      boolean True if the type is derived by restriciton for the reference type

    • setReadOnly

      public void setReadOnly(boolean readOnly, boolean deep)
      Override default behavior so that if deep is true, children are also toggled.
      Overrides:
      setReadOnly in class NodeImpl
      Parameters:
      readOnly - True or false as desired.
      deep - If true, children are also toggled. Note that this will not change the state of an EntityReference or its children, which are always read-only.
      See Also:

    • synchronizeChildren

      protected void synchronizeChildren()
      Override this method in subclass to hook in efficient internal data structure.