XML Standard API: Interface Attr

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## org.w3c.dom
Interface Attr

All Superinterfaces:
  Node

public interface Attr
extends Node

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 |
    "x&#178;=5"
    "x²=5"
    "x&#178;=5"
Built-in character entity |
    "y&lt;6"
    "y<6"
    "y&lt;6"
Literal newline between |
     "x=5&#10;y=6"
    "x=5 y=6"
    "x=5&#10;y=6"
Normalized newline between |
    "x=5
     y=6"
    "x=5 y=6"
    "x=5 y=6"
Entity `e` with literal newline |
     <!ENTITY e '...&#10;...'> [...]> "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.

Fields inherited from interface org.w3c.dom.Node
`ATTRIBUTE_NODE, CDATA_SECTION_NODE, COMMENT_NODE, DOCUMENT_FRAGMENT_NODE, DOCUMENT_NODE, DOCUMENT_POSITION_CONTAINED_BY, DOCUMENT_POSITION_CONTAINS, DOCUMENT_POSITION_DISCONNECTED, DOCUMENT_POSITION_FOLLOWING, DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC, DOCUMENT_POSITION_PRECEDING, DOCUMENT_TYPE_NODE, ELEMENT_NODE, ENTITY_NODE, ENTITY_REFERENCE_NODE, NOTATION_NODE, PROCESSING_INSTRUCTION_NODE, TEXT_NODE`

Method Summary
`java.lang.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.
`java.lang.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(java.lang.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

### getName

    public java.lang.String getName()

  Returns the name of this attribute. If `Node.localName` is different from `null`, this attribute is a qualified name.

### getSpecified

    public 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.

### getValue

    public java.lang.String getValue()

  On retrieval, the value of the attribute is returned as a string. Character and general entity references are replaced with their values. See also the method `getAttribute` on the `Element` interface.
  On setting, this creates a `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()`.
  Some specialized implementations, such as some [SVG 1.1] implementations, may do normalization automatically, even after mutation; in such case, the value on retrieval may differ from the value on setting.

### setValue

    public void setValue(java.lang.String value)
                  throws DOMException

  On retrieval, the value of the attribute is returned as a string. Character and general entity references are replaced with their values. See also the method `getAttribute` on the `Element` interface.
  On setting, this creates a `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()`.
  Some specialized implementations, such as some [SVG 1.1] implementations, may do normalization automatically, even after mutation; in such case, the value on retrieval may differ from the value on setting.
  Throws:
    `DOMException` - NO_MODIFICATION_ALLOWED_ERR: Raised when the node is readonly.

### getOwnerElement

    public Element getOwnerElement()

  The `Element` node this attribute is attached to or `null` if this attribute is not in use.
  Since:
    DOM Level 2

### getSchemaTypeInfo

    public TypeInfo getSchemaTypeInfo()

  The type information associated with this attribute. While the type information contained in this attribute is guarantee to be correct after loading the document or invoking `Document.normalizeDocument()`, `schemaTypeInfo` may not be reliable if the node was moved.
  Since:
    DOM Level 3

### isId

    public boolean isId()

  Returns whether this attribute is known to be of type ID (i.e. to contain an identifier for its owner element) or not. When it is and its value is unique, the `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:
  - If validation occurred using an XML Schema [XML Schema Part 1] while loading the document or while invoking `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] .
  - If validation occurred using a DTD while loading the document or while invoking `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] .
  - from the use of the methods `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.

  - using mechanisms that are outside the scope of this specification, it is then an externally-determined ID attribute. This includes using schema languages different from XML schema and DTD.
  If validation occurred while invoking `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.
  Since:
    DOM Level 3

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