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1 /*
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57
58 package com.sun.org.apache.xerces.internal.dom;
59
60 /**
61  * EntityReference models the XML &entityname; syntax, when used for
62  * entities defined by the DOM. Entities hardcoded into XML, such as
63  * character entities, should instead have been translated into text
64  * by the code which generated the DOM tree.
65  * <P>
66  * An XML processor has the alternative of fully expanding Entities
67  * into the normal document tree. If it does so, no EntityReference nodes
68  * will appear.
69  * <P>
70  * Similarly, non-validating XML processors are not required to read
71  * or process entity declarations made in the external subset or
72  * declared in external parameter entities. Hence, some applications
73  * may not make the replacement value available for Parsed Entities
74  * of these types.
75  * <P>
76  * EntityReference behaves as a read-only node, and the children of
77  * the EntityReference (which reflect those of the Entity, and should
78  * also be read-only) give its replacement value, if any. They are
79  * supposed to automagically stay in synch if the DocumentType is
80  * updated with new values for the Entity.
81  * <P>
82  * The defined behavior makes efficient storage difficult for the DOM
83  * implementor. We can't just look aside to the Entity's definition
84  * in the DocumentType since those nodes have the wrong parent (unless
85  * we can come up with a clever "imaginary parent" mechanism). We
86  * must at least appear to clone those children... which raises the
87  * issue of keeping the reference synchronized with its parent.
88  * This leads me back to the "cached image of centrally defined data"
89  * solution, much as I dislike it.
90  * <P>
91  * For now I have decided, since REC-DOM-Level-1-19980818 doesn't
92  * cover this in much detail, that synchronization doesn't have to be
93  * considered while the user is deep in the tree. That is, if you're
94  * looking within one of the EntityReferennce's children and the Entity
95  * changes, you won't be informed; instead, you will continue to access
96  * the same object -- which may or may not still be part of the tree.
97  * This is the same behavior that obtains elsewhere in the DOM if the
98  * subtree you're looking at is deleted from its parent, so it's
99  * acceptable here. (If it really bothers folks, we could set things
100  * up so deleted subtrees are walked and marked invalid, but that's
101  * not part of the DOM's defined behavior.)
102  * <P>
103  * As a result, only the EntityReference itself has to be aware of
104  * changes in the Entity. And it can take advantage of the same
105  * structure-change-monitoring code I implemented to support
106  * DeepNodeList.
107  *
108  * @version $Id: DeferredEntityReferenceImpl.java,v 1.19 2003/05/08 19:52:40 elena Exp $
109  * @since PR-DOM-Level-1-19980818.
110  */
111 public class DeferredEntityReferenceImpl
112     extends EntityReferenceImpl
113     implements DeferredNode {
114
115     //
116 // Constants
117 //
118
119     /** Serialization version. */
120     static final long serialVersionUID = 390319091370032223L;
121     
122     //
123 // Data
124 //
125
126     /** Node index. */
127     protected transient int fNodeIndex;
128
129     //
130 // Constructors
131 //
132
133     /**
134      * This is the deferred constructor. Only the fNodeIndex is given here.
135      * All other data, can be requested from the ownerDocument via the index.
136      */
137     DeferredEntityReferenceImpl(DeferredDocumentImpl ownerDocument,
138                                 int nodeIndex) {
139         super(ownerDocument, null);
140
141         fNodeIndex = nodeIndex;
142         needsSyncData(true);
143
144     } // <init>(DeferredDocumentImpl,int)
145
146     //
147 // DeferredNode methods
148 //
149
150     /** Returns the node index. */
151     public int getNodeIndex() {
152         return fNodeIndex;
153     }
154
155     //
156 // Protected methods
157 //
158
159     /**
160      * Synchronize the entity data. This is special because of the way
161      * that the "fast" version stores the information.
162      */
163     protected void synchronizeData() {
164
165         // no need to sychronize again
166 needsSyncData(false);
167
168         // get the node data
169 DeferredDocumentImpl ownerDocument =
170             (DeferredDocumentImpl)this.ownerDocument;
171         name = ownerDocument.getNodeName(fNodeIndex);
172         baseURI = ownerDocument.getNodeValue(fNodeIndex);
173         
174     } // synchronizeData()
175
176     /** Synchronize the children. */
177     protected void synchronizeChildren() {
178
179         // no need to synchronize again
180 needsSyncChildren(false);
181
182         // get children
183 isReadOnly(false);
184         DeferredDocumentImpl ownerDocument =
185             (DeferredDocumentImpl) ownerDocument();
186         ownerDocument.synchronizeChildren(this, fNodeIndex);
187         setReadOnly(true, true);
188
189     } // synchronizeChildren()
190
191 } // class DeferredEntityReferenceImpl
192
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