org.apache.xerces.dom.DeferredEntityReferenceImpl Maven / Gradle / Ivy
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* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation and was
* originally based on software copyright (c) 1999, International
* Business Machines, Inc., http://www.apache.org. For more
* information on the Apache Software Foundation, please see
*
* 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.
*
* @version $Id: DeferredEntityReferenceImpl.java,v 1.19 2003/05/08 19:52:40 elena Exp $
* @since PR-DOM-Level-1-19980818.
*/
public class DeferredEntityReferenceImpl
extends EntityReferenceImpl
implements DeferredNode {
//
// Constants
//
/** Serialization version. */
static final long serialVersionUID = 390319091370032223L;
//
// Data
//
/** Node index. */
protected transient int fNodeIndex;
//
// Constructors
//
/**
* This is the deferred constructor. Only the fNodeIndex is given here.
* All other data, can be requested from the ownerDocument via the index.
*/
DeferredEntityReferenceImpl(DeferredDocumentImpl ownerDocument,
int nodeIndex) {
super(ownerDocument, null);
fNodeIndex = nodeIndex;
needsSyncData(true);
} // (DeferredDocumentImpl,int)
//
// DeferredNode methods
//
/** Returns the node index. */
public int getNodeIndex() {
return fNodeIndex;
}
//
// Protected methods
//
/**
* Synchronize the entity data. This is special because of the way
* that the "fast" version stores the information.
*/
protected void synchronizeData() {
// no need to sychronize again
needsSyncData(false);
// get the node data
DeferredDocumentImpl ownerDocument =
(DeferredDocumentImpl)this.ownerDocument;
name = ownerDocument.getNodeName(fNodeIndex);
baseURI = ownerDocument.getNodeValue(fNodeIndex);
} // synchronizeData()
/** Synchronize the children. */
protected void synchronizeChildren() {
// no need to synchronize again
needsSyncChildren(false);
// get children
isReadOnly(false);
DeferredDocumentImpl ownerDocument =
(DeferredDocumentImpl) ownerDocument();
ownerDocument.synchronizeChildren(this, fNodeIndex);
setReadOnly(true, true);
} // synchronizeChildren()
} // class DeferredEntityReferenceImpl