Java example source code file (EntityReferenceImpl.java)
The EntityReferenceImpl.java Java example source code
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/*
* Copyright 1999-2002,2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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* See the License for the specific language governing permissions and
* limitations under the License.
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package com.sun.org.apache.xerces.internal.dom;
import com.sun.org.apache.xerces.internal.util.URI;
import org.w3c.dom.DocumentType;
import org.w3c.dom.EntityReference;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
/**
* 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.
* <P>
* An XML processor has the alternative of fully expanding Entities
* into the normal document tree. If it does so, no EntityReference nodes
* will appear.
* <P>
* 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.
* <P>
* 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.
* <P>
* 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.
* <P>
* 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.)
* <P>
* 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.
*
* @xerces.internal
*
* @author Arnaud Le Hors, IBM
* @author Joe Kesselman, IBM
* @author Andy Clark, IBM
* @author Ralf Pfeiffer, IBM
* @since PR-DOM-Level-1-19980818.
*/
public class EntityReferenceImpl
extends ParentNode
implements EntityReference {
//
// Constants
//
/** Serialization version. */
static final long serialVersionUID = -7381452955687102062L;
//
// Data
//
/** Name of Entity referenced */
protected String name;
/** Base URI*/
protected String baseURI;
/** Entity changes. */
//protected int entityChanges = -1;
/** Enable synchronize. */
//protected boolean fEnableSynchronize = false;
//
// Constructors
//
/** Factory constructor. */
public EntityReferenceImpl(CoreDocumentImpl ownerDoc, String name) {
super(ownerDoc);
this.name = name;
isReadOnly(true);
needsSyncChildren(true);
}
//
// Node methods
//
/**
* 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.
*/
public short getNodeType() {
return Node.ENTITY_REFERENCE_NODE;
}
/**
* Returns the name of the entity referenced
*/
public String getNodeName() {
if (needsSyncData()) {
synchronizeData();
}
return name;
}
/** Clone node. */
public Node cloneNode(boolean deep) {
EntityReferenceImpl er = (EntityReferenceImpl)super.cloneNode(deep);
er.setReadOnly(true, deep);
return er;
}
/**
* 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.
*
* @return The absolute base URI of this node or null.
* @since DOM Level 3
*/
public String getBaseURI() {
if (needsSyncData()) {
synchronizeData();
}
if (baseURI == null) {
DocumentType doctype;
NamedNodeMap entities;
EntityImpl entDef;
if (null != (doctype = getOwnerDocument().getDoctype()) &&
null != (entities = doctype.getEntities())) {
entDef = (EntityImpl)entities.getNamedItem(getNodeName());
if (entDef !=null) {
return entDef.getBaseURI();
}
}
} else if (baseURI != null && baseURI.length() != 0 ) {// attribute value is always empty string
try {
return new URI(baseURI).toString();
}
catch (com.sun.org.apache.xerces.internal.util.URI.MalformedURIException e){
// REVISIT: what should happen in this case?
return null;
}
}
return baseURI;
}
/** NON-DOM: set base uri*/
public void setBaseURI(String uri){
if (needsSyncData()) {
synchronizeData();
}
baseURI = uri;
}
/**
* 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.
* @return String representing a value of this entity ref. or
* null if any node other than EntityReference, Text is encountered
* during computation
*/
protected String getEntityRefValue (){
if (needsSyncChildren()){
synchronizeChildren();
}
String value = "";
if (firstChild != null){
if (firstChild.getNodeType() == Node.ENTITY_REFERENCE_NODE){
value = ((EntityReferenceImpl)firstChild).getEntityRefValue();
}
else if (firstChild.getNodeType() == Node.TEXT_NODE){
value = firstChild.getNodeValue();
}
else {
// invalid to have other types of nodes in attr value
return null;
}
if (firstChild.nextSibling == null){
return value;
}
else {
StringBuffer buff = new StringBuffer(value);
ChildNode next = firstChild.nextSibling;
while (next != null){
if (next.getNodeType() == Node.ENTITY_REFERENCE_NODE){
value = ((EntityReferenceImpl)next).getEntityRefValue();
}
else if (next.getNodeType() == Node.TEXT_NODE){
value = next.getNodeValue();
}
else {
// invalid to have other types of nodes in attr value
return null;
}
buff.append(value);
next = next.nextSibling;
}
return buff.toString();
}
}
return "";
}
/**
* 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.
*/
protected void synchronizeChildren() {
// no need to synchronize again
needsSyncChildren(false);
DocumentType doctype;
NamedNodeMap entities;
EntityImpl entDef;
if (null != (doctype = getOwnerDocument().getDoctype()) &&
null != (entities = doctype.getEntities())) {
entDef = (EntityImpl)entities.getNamedItem(getNodeName());
// No Entity by this name, stop here.
if (entDef == null)
return;
// If entity's definition exists, clone its kids
isReadOnly(false);
for (Node defkid = entDef.getFirstChild();
defkid != null;
defkid = defkid.getNextSibling()) {
Node newkid = defkid.cloneNode(true);
insertBefore(newkid, null);
}
setReadOnly(true, true);
}
}
/**
* NON-DOM: sets the node and its children value.
* <P>
* Note: make sure that entity reference and its kids could be set readonly.
*/
public void setReadOnly(boolean readOnly, boolean deep) {
if (needsSyncData()) {
synchronizeData();
}
if (deep) {
if (needsSyncChildren()) {
synchronizeChildren();
}
// Recursively set kids
for (ChildNode mykid = firstChild;
mykid != null;
mykid = mykid.nextSibling) {
mykid.setReadOnly(readOnly,true);
}
}
isReadOnly(readOnly);
} // setReadOnly(boolean,boolean)
/**
* Enable the synchronize method which may do cloning. This method is enabled
* when the parser is done with an EntityReference.
/***
// revisit: enable editing of Entity
public void enableSynchronize(boolean enableSynchronize) {
fEnableSynchronize= enableSynchronize;
}
/***/
/**
* EntityReference's children are a reflection of those defined in the
* named Entity. This method updates them if the Entity is changed.
* <P>
* It is unclear what the least-cost resynch mechanism is.
* If we expect the kids to be shallow, and/or expect changes
* to the Entity contents to be rare, wiping them all out
* and recloning is simplest.
* <P>
* If we expect them to be deep,
* it might be better to first decide which kids (if any)
* persist, and keep the ones (if any) that are unchanged
* rather than doing all the work of cloning them again.
* But that latter gets into having to convolve the two child lists,
* insert new information in the right order (and possibly reorder
* the existing kids), and a few other complexities that I really
* don't want to deal with in this implementation.
* <P>
* Note that if we decide that we need to update the EntityReference's
* contents, we have to turn off the readOnly flag temporarily to do so.
* When we get around to adding multitasking support, this whole method
* should probably be an atomic operation.
*
* @see DocumentTypeImpl
* @see EntityImpl
*/
// The Xerces parser invokes callbacks for startEnityReference
// the parsed value of the entity EACH TIME, so it is actually
// easier to create the nodes through the callbacks rather than
// clone the Entity.
/***
// revisit: enable editing of Entity
private void synchronize() {
if (!fEnableSynchronize) {
return;
}
DocumentType doctype;
NamedNodeMap entities;
EntityImpl entDef;
if (null != (doctype = getOwnerDocument().getDoctype()) &&
null != (entities = doctype.getEntities())) {
entDef = (EntityImpl)entities.getNamedItem(getNodeName());
// No Entity by this name. If we had a change count, reset it.
if(null==entDef)
entityChanges=-1;
// If no kids availalble, wipe any pre-existing children.
// (See discussion above.)
// Note that we have to use the superclass to avoid recursion
// through Synchronize.
readOnly=false;
if(null==entDef || !entDef.hasChildNodes())
for(Node kid=super.getFirstChild();
kid!=null;
kid=super.getFirstChild())
removeChild(kid);
// If entity's definition changed, clone its kids
// (See discussion above.)
if(null!=entDef && entDef.changes!=entityChanges) {
for(Node defkid=entDef.getFirstChild();
defkid!=null;
defkid=defkid.getNextSibling()) {
NodeImpl newkid=(NodeImpl) defkid.cloneNode(true);
newkid.setReadOnly(true,true);
insertBefore(newkid,null);
}
entityChanges=entDef.changes;
}
readOnly=true;
}
}
/***/
} // class EntityReferenceImpl
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