Xerces2 Implementation: Class EntityReferenceImpl

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## 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, org.w3c.dom.EntityReference, org.w3c.dom.events.EventTarget, org.w3c.dom.Node, org.w3c.dom.NodeList, java.io.Serializable

Direct Known Subclasses:
  DeferredEntityReferenceImpl

public class EntityReferenceImpl
extends ParentNode
implements org.w3c.dom.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.

# 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: EntityReferenceImpl.java 447266 2006-09-18 05:57:49Z mrglavas $
Author:
  Arnaud Le Hors, IBM, Joe Kesselman, IBM, Andy Clark, IBM, Ralf Pfeiffer, IBM
See Also:
  Serialized Form

Field Summary
`protected java.lang.String` | `baseURI` Base URI
`protected java.lang.String` | `name` Name of Entity referenced

Fields inherited from class org.apache.xerces.dom.ParentNode
`firstChild, fNodeListCache, ownerDocument`

Fields inherited from class org.apache.xerces.dom.ChildNode
`nextSibling, previousSibling`

Fields inherited from class org.apache.xerces.dom.NodeImpl
`DOCUMENT_POSITION_CONTAINS, DOCUMENT_POSITION_DISCONNECTED, DOCUMENT_POSITION_FOLLOWING, DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC, DOCUMENT_POSITION_IS_CONTAINED, DOCUMENT_POSITION_PRECEDING, ELEMENT_DEFINITION_NODE, FIRSTCHILD, flags, HASSTRING, ID, IGNORABLEWS, NORMALIZED, OWNED, ownerNode, READONLY, SPECIFIED, SYNCCHILDREN, SYNCDATA, TREE_POSITION_ANCESTOR, TREE_POSITION_DESCENDANT, TREE_POSITION_DISCONNECTED, TREE_POSITION_EQUIVALENT, TREE_POSITION_FOLLOWING, TREE_POSITION_PRECEDING, TREE_POSITION_SAME_NODE`

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`

Constructor Summary
`EntityReferenceImpl(CoreDocumentImpl ownerDoc, java.lang.String name)` Factory constructor.

Method Summary
`org.w3c.dom.Node` | `cloneNode(boolean deep)` Clone node.
`java.lang.String` | `getBaseURI()` Returns the absolute base URI of this node or null if the implementation wasn't able to obtain an absolute URI.
`protected java.lang.String` | `getEntityRefValue()` NON-DOM: compute string representation of the entity reference.
`java.lang.String` | `getNodeName()` Returns the name of the entity referenced
`short` | `getNodeType()` A short integer indicating what type of node this is.
`void` | `setBaseURI(java.lang.String uri)` NON-DOM: set base uri
`void` | `setReadOnly(boolean readOnly, boolean deep)` NON-DOM: sets the node and its children value.
`protected void` | `synchronizeChildren()` EntityReference's children are a reflection of those defined in the named Entity.

Methods inherited from class org.apache.xerces.dom.ParentNode
`getChildNodes, getChildNodesUnoptimized, getFirstChild, getLastChild, getLength, getOwnerDocument, getTextContent, hasChildNodes, insertBefore, isEqualNode, item, normalize, removeChild, replaceChild, setOwnerDocument, setTextContent`

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, compareDocumentPosition, compareTreePosition, dispatchEvent, getAttributes, getContainer, getFeature, getLocalName, getNamespaceURI, getNodeNumber, getNodeValue, getPrefix, getReadOnly, getUserData, getUserData, getUserDataRecord, hasAttributes, isDefaultNamespace, isSameNode, isSupported, lookupNamespaceURI, lookupPrefix, needsSyncChildren, removeEventListener, setNodeValue, setPrefix, setUserData, 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, compareDocumentPosition, getAttributes, getChildNodes, getFeature, getFirstChild, getLastChild, getLocalName, getNamespaceURI, getNextSibling, getNodeValue, getOwnerDocument, getParentNode, getPrefix, getPreviousSibling, getTextContent, getUserData, hasAttributes, hasChildNodes, insertBefore, isDefaultNamespace, isEqualNode, isSameNode, isSupported, lookupNamespaceURI, lookupPrefix, normalize, removeChild, replaceChild, setNodeValue, setPrefix, setTextContent, setUserData`

Field Detail

### name

    protected java.lang.String name

  Name of Entity referenced

### baseURI

    protected java.lang.String baseURI

  Base URI

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 `org.w3c.dom.Node`
  Overrides:
    `getNodeType` in class `NodeImpl`

### getNodeName

    public java.lang.String getNodeName()

  Returns the name of the entity referenced
  Specified by:
    `getNodeName` in interface `org.w3c.dom.Node`
  Overrides:
    `getNodeName` in class `NodeImpl`

### cloneNode

    public org.w3c.dom.Node cloneNode(boolean deep)

  Clone node.
  Specified by:
    `cloneNode` in interface `org.w3c.dom.Node`
  Overrides:
    `cloneNode` in class `ParentNode`
  Following copied from interface: `org.w3c.dom.Node`
  Parameters:
    `deep` - If `true`, recursively clone the subtree under the specified node; if `false`, clone only the node itself (and its attributes, if it is an `Element`).
  Returns:
    The duplicate node.

### getBaseURI

    public java.lang.String getBaseURI()

  Returns the absolute base URI of this node or null if the implementation wasn't able to obtain an absolute URI. Note: If the URI is malformed, a null is returned.
  Specified by:
    `getBaseURI` in interface `org.w3c.dom.Node`
  Overrides:
    `getBaseURI` in class `NodeImpl`
  Returns:
    The absolute base URI of this node or null.
  Since:
    DOM Level 3

### setBaseURI

    public void setBaseURI(java.lang.String uri)

  NON-DOM: set base uri

### getEntityRefValue

    protected java.lang.String getEntityRefValue()

  NON-DOM: compute string representation of the entity reference. This method is used to retrieve a string value for an attribute node that has child nodes.
  Returns:
    String representing a value of this entity ref. or null if any node other than EntityReference, Text is encountered during computation

### synchronizeChildren

    protected void synchronizeChildren()

  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 support editing the Entity though, since this only called once for all.
  Overrides:
    `synchronizeChildren` in class `ParentNode`

### setReadOnly

    public void setReadOnly(boolean readOnly,
                            boolean deep)

  NON-DOM: sets the node and its children value.

  Note: make sure that entity reference and its kids could be set readonly.

  Overrides:
    `setReadOnly` in class `ParentNode`
  Following copied from class: `org.apache.xerces.dom.ParentNode`
  See Also:
    `

    Note: this will not change the state of an EntityReference or its children, which are always read-only.

    `

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