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Attr
interface represents an attribute in an Element
object.Typically the allowable values for the attribute are
defined in a documenttype definition.
Attr
objects inherit the Node
interface, but
since they are not actually child nodes of the element they describe, the
DOM does not consider them part of the document tree. Thus, the
Node
attributes parentNode
, previousSibling
, and nextSibling
have a null value for Attr
objects. The DOM takes the view that attributes are properties of
elements rather than having a separate identity from the elements they
are associated with; this should make it more efficient to implement such
features as default attributes associated with all elements of a given
type. Furthermore, Attr
nodes may not be immediate children
of a DocumentFragment
. However, they can be associated with
Element
nodes contained within a DocumentFragment
. In short, users and implementors of the DOM need to be aware that
Attr
nodes have some things in common with other objects
inheriting the Node
interface, but they also are quite
distinct.
The attribute's effective value is determined as follows: if this
attribute has been explicitly assigned any value, that value is the
attribute's effective value; otherwise, if there is a declaration for
this attribute, and that declaration includes a default value, then that
default value is the attribute's effective value; otherwise, the
attribute does not exist on this element in the structure model until it
has been explicitly added. Note that the nodeValue
attribute on the Attr
instance can also be used to retrieve
the string version of the attribute's value(s).
In XML, where the value of an attribute can contain entity references,
the child nodes of the Attr
node provide a representation in
which entity references are not expanded. These child nodes may be either
Text
or EntityReference
nodes. Because the
attribute type may be unknown, there are no tokenized attribute values.
true
; otherwise, it is false
.
public abstract String getName()
public abstract boolean getSpecified()
true
; otherwise, it is false
. Note
that the implementation is in charge of this attribute, not the user. If
the user changes the value of the attribute (even if it ends up having
the same value as the default value) then the specified
flag is automatically flipped to true
. To re-specify the
attribute as the default value from the DTD, the user must delete the
attribute. The implementation will then make a new attribute available
with specified
set to false
and the default
value (if one exists). * specified
is true
, and the value is the
assigned value. If the attribute has no assigned value in the document
and has a default value in the DTD, then specified
is
false
, and the value is the default value in the DTD. If
the attribute has no assigned value in the document and has a value of
#IMPLIED in the DTD, then the attribute does not appear in the
structure model of the document.
public abstract String getValue()
Text
node with the unparsed
contents of the string.
public abstract void setValue(String value)
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