org.apache.xerces.dom
Class EntityReferenceImpl

java.lang.Object
  |
  +--org.apache.xerces.dom.NodeImpl
        |
        +--org.apache.xerces.dom.ChildNode
              |
              +--org.apache.xerces.dom.ParentNode
                    |
                    +--org.apache.xerces.dom.EntityReferenceImpl
All Implemented Interfaces:
java.lang.Cloneable, EntityReference, EventTarget, Node, NodeList, java.io.Serializable
Direct Known Subclasses:
DeferredEntityReferenceImpl

public class EntityReferenceImpl
extends ParentNode
implements EntityReference

EntityReference models the XML &entityname; syntax, when used for entities defined by the DOM. Entities hardcoded into XML, such as character entities, should instead have been translated into text by the code which generated the DOM tree.

An XML processor has the alternative of fully expanding Entities into the normal document tree. If it does so, no EntityReference nodes will appear.

Similarly, non-validating XML processors are not required to read or process entity declarations made in the external subset or declared in external parameter entities. Hence, some applications may not make the replacement value available for Parsed Entities of these types.

EntityReference behaves as a read-only node, and the children of the EntityReference (which reflect those of the Entity, and should also be read-only) give its replacement value, if any. They are supposed to automagically stay in synch if the DocumentType is updated with new values for the Entity.

The defined behavior makes efficient storage difficult for the DOM implementor. We can't just look aside to the Entity's definition in the DocumentType since those nodes have the wrong parent (unless we can come up with a clever "imaginary parent" mechanism). We must at least appear to clone those children... which raises the issue of keeping the reference synchronized with its parent. This leads me back to the "cached image of centrally defined data" solution, much as I dislike it.

For now I have decided, since REC-DOM-Level-1-19980818 doesn't cover this in much detail, that synchronization doesn't have to be considered while the user is deep in the tree. That is, if you're looking within one of the EntityReferennce's children and the Entity changes, you won't be informed; instead, you will continue to access the same object -- which may or may not still be part of the tree. This is the same behavior that obtains elsewhere in the DOM if the subtree you're looking at is deleted from its parent, so it's acceptable here. (If it really bothers folks, we could set things up so deleted subtrees are walked and marked invalid, but that's not part of the DOM's defined behavior.)

As a result, only the EntityReference itself has to be aware of changes in the Entity. And it can take advantage of the same structure-change-monitoring code I implemented to support DeepNodeList.

Since:
PR-DOM-Level-1-19980818.
Version:
 
Author:
Arnaud Le Hors, IBM, Joe Kesselman, IBM, Andy Clark, IBM, Ralf Pfeiffer, IBM
See Also:
Serialized Form

Field Summary
protected  java.lang.String name
          Name of Entity referenced
 
Fields inherited from class org.apache.xerces.dom.ParentNode
fCachedChild, fCachedChildIndex, fCachedLength, firstChild, ownerDocument
 
Fields inherited from class org.apache.xerces.dom.ChildNode
nextSibling, previousSibling
 
Fields inherited from class org.apache.xerces.dom.NodeImpl
ELEMENT_DEFINITION_NODE, FIRSTCHILD, flags, HASSTRING, IGNORABLEWS, OWNED, ownerNode, READONLY, SPECIFIED, SYNCCHILDREN, SYNCDATA, UNNORMALIZED
 
Fields inherited from interface org.w3c.dom.Node
ATTRIBUTE_NODE, CDATA_SECTION_NODE, COMMENT_NODE, DOCUMENT_FRAGMENT_NODE, DOCUMENT_NODE, DOCUMENT_TYPE_NODE, ELEMENT_NODE, ENTITY_NODE, ENTITY_REFERENCE_NODE, NOTATION_NODE, PROCESSING_INSTRUCTION_NODE, TEXT_NODE
 
Constructor Summary
EntityReferenceImpl(CoreDocumentImpl ownerDoc, java.lang.String name)
          Factory constructor.
 
Method Summary
 NodeList getChildNodes()
          Perform synchronize() before accessing children.
 Node getFirstChild()
          Perform synchronize() before accessing children.
 Node getLastChild()
          Perform synchronize() before accessing children.
 int getLength()
          Query the number of children in the entity definition.
 java.lang.String getNodeName()
          Returns the name of the entity referenced
 short getNodeType()
          A short integer indicating what type of node this is.
 boolean hasChildNodes()
          Returns whether this node has any children.
 Node item(int index)
          Returns the node at the given index.
protected  void synchronize()
          EntityReference's children are a reflection of those defined in the named Entity.
 
Methods inherited from class org.apache.xerces.dom.ParentNode
cloneNode, getChildNodesUnoptimized, getOwnerDocument, insertBefore, normalize, removeChild, replaceChild, setReadOnly, synchronizeChildren
 
Methods inherited from class org.apache.xerces.dom.ChildNode
getNextSibling, getParentNode, getPreviousSibling
 
Methods inherited from class org.apache.xerces.dom.NodeImpl
addEventListener, appendChild, changed, changes, dispatchEvent, getAttributes, getLocalName, getNamespaceURI, getNodeValue, getPrefix, getReadOnly, getUserData, hasAttributes, isSupported, removeEventListener, setNodeValue, setPrefix, setUserData, synchronizeData, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface org.w3c.dom.Node
appendChild, cloneNode, getAttributes, getLocalName, getNamespaceURI, getNextSibling, getNodeValue, getOwnerDocument, getParentNode, getPrefix, getPreviousSibling, hasAttributes, insertBefore, isSupported, normalize, removeChild, replaceChild, setNodeValue, setPrefix
 

Field Detail

name

protected java.lang.String name
Name of Entity referenced
Constructor Detail

EntityReferenceImpl

public EntityReferenceImpl(CoreDocumentImpl ownerDoc,
                           java.lang.String name)
Factory constructor.
Method Detail

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
Overrides:
getNodeType in class NodeImpl

getNodeName

public java.lang.String getNodeName()
Returns the name of the entity referenced
Specified by:
getNodeName in interface Node
Overrides:
getNodeName in class NodeImpl

getChildNodes

public NodeList getChildNodes()
Perform synchronize() before accessing children.
Specified by:
getChildNodes in interface Node
Overrides:
getChildNodes in class ParentNode
Returns:
org.w3c.dom.NodeList

getFirstChild

public Node getFirstChild()
Perform synchronize() before accessing children.
Specified by:
getFirstChild in interface Node
Overrides:
getFirstChild in class ParentNode
Returns:
org.w3c.dom.NodeList

getLastChild

public Node getLastChild()
Perform synchronize() before accessing children.
Specified by:
getLastChild in interface Node
Overrides:
getLastChild in class ParentNode
Returns:
org.w3c.dom.NodeList

getLength

public int getLength()
Query the number of children in the entity definition. (A bit more work than asking locally, but may be able to avoid or defer building the clone subtree.)
Overrides:
getLength in class ParentNode
Returns:
org.w3c.dom.NodeList

hasChildNodes

public boolean hasChildNodes()
Returns whether this node has any children.
Specified by:
hasChildNodes in interface Node
Overrides:
hasChildNodes in class ParentNode
Returns:
boolean

item

public Node item(int index)
Returns the node at the given index.
Overrides:
item in class ParentNode
Following copied from class: org.apache.xerces.dom.ParentNode
Parameters:
index - int
Returns:
org.w3c.dom.Node

synchronize

protected void synchronize()
EntityReference's children are a reflection of those defined in the named Entity. This method creates them if they haven't been created yet. This doesn't really support editing the Entity though.


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