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Common DOM API | |||||||||
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public interface Attr
The Attr interface represents an attribute in an
Element object. Typically the allowable values for the
attribute are defined in a schema associated with the document.
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 Node.nodeValue
attribute on the Attr instance can also be used to retrieve
the string version of the attribute's value(s).
If the attribute was not explicitly given a value in the instance
document but has a default value provided by the schema associated with
the document, an attribute node will be created with
specified set to false. Removing attribute
nodes for which a default value is defined in the schema generates a new
attribute node with the default value and specified set to
false. If validation occurred while invoking
Document.normalizeDocument(), attribute nodes with
specified equals to false are recomputed
according to the default attribute values provided by the schema. If no
default value is associate with this attribute in the schema, the
attribute node is discarded.
In XML, where the value of an attribute can contain entity references,
the child nodes of the Attr node may be either
Text or EntityReference nodes (when these are
in use; see the description of EntityReference for
discussion).
The DOM Core represents all attribute values as simple strings, even if the DTD or schema associated with the document declares them of some specific type such as tokenized.
The way attribute value normalization is performed by the DOM
implementation depends on how much the implementation knows about the
schema in use. Typically, the value and
nodeValue attributes of an Attr node initially
returns the normalized value given by the parser. It is also the case
after Document.normalizeDocument() is called (assuming the
right options have been set). But this may not be the case after
mutation, independently of whether the mutation is performed by setting
the string value directly or by changing the Attr child
nodes. In particular, this is true when character
references are involved, given that they are not represented in the DOM and they
impact attribute value normalization. On the other hand, if the
implementation knows about the schema in use when the attribute value is
changed, and it is of a different type than CDATA, it may normalize it
again at that time. This is especially true of specialized DOM
implementations, such as SVG DOM implementations, which store attribute
values in an internal form different from a string.
The following table gives some examples of the relations between the attribute value in the original document (parsed attribute), the value as exposed in the DOM, and the serialization of the value:
| Examples | Parsed attribute value | Initial Attr.value |
Serialized attribute value |
|---|---|---|---|
| Character reference |
"x²=5" |
"x?=5" |
"x²=5" |
| Built-in character entity |
"y<6" |
"y<6" |
"y<6" |
| Literal newline between |
"x=5 y=6" |
"x=5 y=6" |
"x=5 y=6" |
| Normalized newline between |
"x=5 y=6" |
"x=5 y=6" |
"x=5 y=6" |
Entity e with literal newline |
<!ENTITY e '... ...'> [...]> "x=5&e;y=6" |
Dependent on Implementation and Load Options | Dependent on Implementation and Load/Save Options |
See also the Document Object Model (DOM) Level 3 Core Specification.
| Field Summary |
|---|
| Method Summary | |
|---|---|
String |
getName()
Returns the name of this attribute. |
Element |
getOwnerElement()
The Element node this attribute is attached to or
null if this attribute is not in use. |
TypeInfo |
getSchemaTypeInfo()
The type information associated with this attribute. |
boolean |
getSpecified()
True if this attribute was explicitly given a value in
the instance document, false otherwise. |
String |
getValue()
On retrieval, the value of the attribute is returned as a string. |
boolean |
isId()
Returns whether this attribute is known to be of type ID (i.e. |
void |
setValue(String value)
On retrieval, the value of the attribute is returned as a string. |
| Methods inherited from interface org.w3c.dom.Node |
|---|
appendChild, cloneNode, compareDocumentPosition, getAttributes, getBaseURI, getChildNodes, getFeature, getFirstChild, getLastChild, getLocalName, getNamespaceURI, getNextSibling, getNodeName, getNodeType, getNodeValue, getOwnerDocument, getParentNode, getPrefix, getPreviousSibling, getTextContent, getUserData, hasAttributes, hasChildNodes, insertBefore, isDefaultNamespace, isEqualNode, isSameNode, isSupported, lookupNamespaceURI, lookupPrefix, normalize, removeChild, replaceChild, setNodeValue, setPrefix, setTextContent, setUserData |
| Method Detail |
|---|
String getName()
Node.localName is
different from null, this attribute is a qualified name.
boolean getSpecified()
True if this attribute was explicitly given a value in
the instance document, false otherwise. If the
application changed the value of this attribute node (even if it ends
up having the same value as the default value) then it is set to
true. The implementation may handle attributes with
default values from other schemas similarly but applications should
use Document.normalizeDocument() to guarantee this
information is up-to-date.
String getValue()
getAttribute on the
Element interface.
Text node with the unparsed
contents of the string, i.e. any characters that an XML processor
would recognize as markup are instead treated as literal text. See
also the method Element.setAttribute().
void setValue(String value)
throws DOMException
getAttribute on the
Element interface.
Text node with the unparsed
contents of the string, i.e. any characters that an XML processor
would recognize as markup are instead treated as literal text. See
also the method Element.setAttribute().
DOMException - NO_MODIFICATION_ALLOWED_ERR: Raised when the node is readonly.Element getOwnerElement()
Element node this attribute is attached to or
null if this attribute is not in use.
TypeInfo getSchemaTypeInfo()
Document.normalizeDocument(), schemaTypeInfo
may not be reliable if the node was moved.
boolean isId()
ownerElement of this attribute
can be retrieved using the method Document.getElementById
. The implementation could use several ways to determine if an
attribute node is known to contain an identifier:
Document.normalizeDocument(), the post-schema-validation
infoset contributions (PSVI contributions) values are used to
determine if this attribute is a schema-determined ID attribute using
the
schema-determined ID definition in [XPointer]
.
Document.normalizeDocument(), the infoset [type definition] value is used to determine if this attribute is a DTD-determined ID
attribute using the
DTD-determined ID definition in [XPointer]
.
Element.setIdAttribute(),
Element.setIdAttributeNS(), or
Element.setIdAttributeNode(), i.e. it is an
user-determined ID attribute;
Note: XPointer framework (see section 3.2 in [XPointer] ) consider the DOM user-determined ID attribute as being part of the XPointer externally-determined ID definition.
Document.normalizeDocument(), all user-determined ID
attributes are reset and all attribute nodes ID information are then
reevaluated in accordance to the schema used. As a consequence, if
the Attr.schemaTypeInfo attribute contains an ID type,
isId will always return true.
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