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57
58 package org.apache.soap.util.xml;
59
60 import java.io.*;
61 import java.util.*;
62 import org.apache.soap.util.xml.* ;
63
64 /**
65  * This class implements a namespace stack for XML apps to use. If
66  * you need to keep track of namespaces in scope, then this class is
67  * for you. Every time you enter a new element and wish to add some
68  * namespace declarations that are to be visible within that
69  * element, you should call <tt>pushScope</tt> to create a new
70  * scope. Then, call <tt>addNSDeclaration</tt> any number of times to
71  * add new declarations for that scope. Scopes nest inside out; that
72  * is, any NS declaration added into a scope is visible from any
73  * scopes that are pushed later. When you want to see whether an NS
74  * declaration has already been made for a certain URI, you should
75  * call <tt>getPrefixInScopeForURI</tt> to get the prefix that has
76  * been bound to that URI. There is a covenience version of
77  * <tt>addNSDecalration</tt> which can be used if you want me to give
78  * you a not-so-random, yet unique, prefix for your namespace
79  * declaration.
80  *
81  * @author Sanjiva Weerawarana (sanjiva@watson.ibm.com)
82  */
83 public class NSStack {
84   Vector nss = new Vector (); // vector holding vectors of ns decls (stack)
85 int nssCount = 0; // number of items on the stack
86 Vector tos; // the vector @ the top of the stack
87 private final static String JavaDoc nsPrefixPrefix = "ns";
88   private int nsPrefixCount = 1;
89
90   /**
91    * Enter a new scope: after calling this I'm ready to accept new
92    * declarations into that scope.
93    */
94   public void pushScope () {
95     nss.addElement (tos = new Vector ());
96     nssCount++;
97   }
98
99   /**
100    * Leave a scope: this removes any NS declarations that were added
101    * in the last scope. Note that I don't bother to validate that you
102    * don't call popScope too many times; that's your problem.
103    */
104   public void popScope () {
105     nss.removeElementAt (--nssCount);
106     tos = (nssCount != 0) ? (Vector) nss.elementAt (nssCount-1) : null;
107   }
108
109   /**
110    * Add a new declaration to the current scope. This is visible within
111    * the current scope as well as from any nested scopes.
112    *
113    * @param prefix the prefix to be used for this namespace
114    * @param URI the namespace name of this namespace.
115    */
116   synchronized public void addNSDeclaration (String JavaDoc prefix, String JavaDoc URI) {
117     tos.addElement (new NSDecl (prefix, URI));
118   }
119
120   /**
121    * Add a new declaration to the current scope using a unique prefix
122    * and return the prefix. This is useful when one just wants to add a
123    * decl and doesn't want to have to deal with creating unique prefixes.
124    * If the namespace name is already declared and in scope, then the
125    * previously declared prefix is returned.
126    *
127    * @param URI the namespace name of this namespace
128    * @return the unique prefix created or previously declared
129    * for this namespace
130    */
131   synchronized public String JavaDoc addNSDeclaration (String JavaDoc URI) {
132     String JavaDoc uniquePrefix = getPrefixFromURI (URI);
133     if (uniquePrefix == null) {
134       do {
135               uniquePrefix = nsPrefixPrefix + nsPrefixCount++;
136       } while (getURIFromPrefix (uniquePrefix) != null);
137       addNSDeclaration (uniquePrefix, URI);
138     }
139     return uniquePrefix;
140   }
141
142   /**
143    * Return the prefix associated with the given namespace name by
144    * looking thru all the namespace declarations that are in scope.
145    *
146    * @param URI the namespace name for whom a declared prefix is desired
147    * @return the prefix or null if namespace name not found
148    */
149   public String JavaDoc getPrefixFromURI (String JavaDoc URI) {
150     for (int i = nssCount-1; i >= 0; i--) {
151       Vector scope = (Vector) nss.elementAt (i);
152       for (Enumeration e = scope.elements (); e.hasMoreElements (); ) {
153         NSDecl nsd = (NSDecl) e.nextElement ();
154         if (nsd.URI.equals (URI)) {
155           return nsd.prefix;
156         }
157       }
158     }
159     return null;
160   }
161
162   /**
163    * Return the prefix associated with the given namespace name by
164    * looking thru all the namespace declarations that are in scope.
165    * If the namespace declaration is not found, create one and
166    * return the generated prefix.
167    *
168    * @param URI the namespace name for whom a declared prefix is desired
169    * @return the prefix (will never return null)
170    */
171   synchronized public String JavaDoc getPrefixFromURI (String JavaDoc namespaceURI,
172                                                Writer sink)
173     throws IOException {
174     String JavaDoc prefix = getPrefixFromURI (namespaceURI);
175
176     if (prefix == null) {
177       prefix = addNSDeclaration (namespaceURI);
178
179       sink.write (" xmlns:" + prefix + "=\"" + namespaceURI + '\"');
180     }
181
182     return prefix;
183   }
184
185   /**
186    * Return the namespace name associated with the given prefix by
187    * looking thru all the namespace declarations that are in scope.
188    *
189    * @param prefix the prefix for whom a declared namespace name is desired
190    * @return the namespace name or null if prefix not found
191    */
192   public String JavaDoc getURIFromPrefix (String JavaDoc prefix) {
193     for (int i = nssCount-1; i >= 0; i--) {
194       Vector scope = (Vector) nss.elementAt (i);
195       for (Enumeration e = scope.elements (); e.hasMoreElements (); ) {
196         NSDecl nsd = (NSDecl) e.nextElement ();
197         if (nsd.prefix.equals (prefix)) {
198           return nsd.URI;
199         }
200       }
201     }
202     return null;
203   }
204
205   // MJD - debug
206 public String JavaDoc toString()
207   {
208     return nss.toString();
209   }
210   // MJD - debug
211 }
212
213
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