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Java > Open Source Codes > com > sun > org > apache > xml > internal > resolver > readers > DOMCatalogReader


1 // DOMCatalogReader.java - Read XML Catalog files
2
3 /*
4  * Copyright 2001-2004 The Apache Software Foundation or its licensors,
5  * as applicable.
6  *
7  * Licensed under the Apache License, Version 2.0 (the "License");
8  * you may not use this file except in compliance with the License.
9  * You may obtain a copy of the License at
10  *
11  * http://www.apache.org/licenses/LICENSE-2.0
12  *
13  * Unless required by applicable law or agreed to in writing, software
14  * distributed under the License is distributed on an "AS IS" BASIS,
15  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16  * See the License for the specific language governing permissions and
17  * limitations under the License.
18  */
19
20 package com.sun.org.apache.xml.internal.resolver.readers;
21
22 import java.util.Hashtable JavaDoc;
23 import java.io.IOException JavaDoc;
24 import java.io.InputStream JavaDoc;
25 import java.net.URL JavaDoc;
26 import java.net.URLConnection JavaDoc;
27 import java.net.MalformedURLException JavaDoc;
28
29 import javax.xml.parsers.DocumentBuilderFactory JavaDoc;
30 import javax.xml.parsers.DocumentBuilder JavaDoc;
31 import javax.xml.parsers.ParserConfigurationException JavaDoc;
32
33 import com.sun.org.apache.xml.internal.resolver.Catalog;
34 import com.sun.org.apache.xml.internal.resolver.CatalogException;
35 import com.sun.org.apache.xml.internal.resolver.readers.CatalogReader;
36 import com.sun.org.apache.xml.internal.resolver.helpers.Namespaces;
37
38 import org.xml.sax.SAXException JavaDoc;
39 import org.w3c.dom.*;
40
41 /**
42  * A DOM-based CatalogReader.
43  *
44  * <p>This class is used to read XML Catalogs using the DOM. This reader
45  * has an advantage over the SAX-based reader that it can analyze the
46  * DOM tree rather than simply a series of SAX events. It has the disadvantage
47  * that it requires all of the code necessary to build and walk a DOM
48  * tree.</p>
49  *
50  * <p>Since the choice of CatalogReaders (in the InputStream case) can only
51  * be made on the basis of MIME type, the following problem occurs: only
52  * one CatalogReader can exist for all XML mime types. In order to get
53  * around this problem, the DOMCatalogReader relies on a set of external
54  * CatalogParsers to actually build the catalog.</p>
55  *
56  * <p>The selection of CatalogParsers is made on the basis of the QName
57  * of the root element of the document.</p>
58  *
59  * <p>This class requires the <a HREF="http://java.sun.com/aboutJava/communityprocess/final/jsr005/index.html">Java API for XML Parsing</a>.</p>
60  *
61  * @see Catalog
62  * @see CatalogReader
63  * @see SAXCatalogReader
64  * @see TextCatalogReader
65  * @see DOMCatalogParser
66  *
67  * @author Norman Walsh
68  * <a HREF="mailto:Norman.Walsh@Sun.COM">Norman.Walsh@Sun.COM</a>
69  *
70  * @version 1.0
71  */
72 public class DOMCatalogReader implements CatalogReader {
73   /**
74    * Mapping table from QNames to CatalogParser classes.
75    *
76    * <p>Each key in this hash table has the form "elementname"
77    * or "{namespaceuri}elementname". The former is used if the
78    * namespace URI is null.</p>
79    */
80   protected Hashtable JavaDoc namespaceMap = new Hashtable JavaDoc();
81
82   /**
83    * Add a new parser to the reader.
84    *
85    * <p>This method associates the specified parserClass with the
86    * namespaceURI/rootElement names specified.</p>
87    *
88    * @param namespaceURI The namespace URI. <em>Not</em> the prefix.
89    * @param rootElement The name of the root element.
90    * @param parserClass The name of the parserClass to instantiate
91    * for this kind of catalog.
92    */
93   public void setCatalogParser(String JavaDoc namespaceURI,
94                    String JavaDoc rootElement,
95                    String JavaDoc parserClass) {
96     if (namespaceURI == null) {
97       namespaceMap.put(rootElement, parserClass);
98     } else {
99       namespaceMap.put("{"+namespaceURI+"}"+rootElement, parserClass);
100     }
101   }
102
103   /**
104    * Get the name of the parser class for a given catalog type.
105    *
106    * <p>This method returns the parserClass associated with the
107    * namespaceURI/rootElement names specified.</p>
108    *
109    * @param namespaceURI The namespace URI. <em>Not</em> the prefix.
110    * @param rootElement The name of the root element.
111    * @return The parser class.
112    */
113   public String JavaDoc getCatalogParser(String JavaDoc namespaceURI,
114                  String JavaDoc rootElement) {
115     if (namespaceURI == null) {
116       return (String JavaDoc) namespaceMap.get(rootElement);
117     } else {
118       return (String JavaDoc) namespaceMap.get("{"+namespaceURI+"}"+rootElement);
119     }
120   }
121
122   /**
123    * Null constructor; something for subclasses to call.
124    */
125   public DOMCatalogReader() { }
126
127   /**
128    * Read a catalog from an input stream.
129    *
130    * <p>This class reads a catalog from an input stream:</p>
131    *
132    * <ul>
133    * <li>Based on the QName of the root element, it determines which
134    * parser to instantiate for this catalog.</li>
135    * <li>It constructs a DOM Document from the catalog and</li>
136    * <li>For each child of the root node, it calls the parser's
137    * parseCatalogEntry method. This method is expected to make
138    * appropriate calls back into the catalog to add entries for the
139    * entries in the catalog. It is free to do this in whatever manner
140    * is appropriate (perhaps using just the node passed in, perhaps
141    * wandering arbitrarily throughout the tree).</li>
142    * </ul>
143    *
144    * @param catalog The catalog for which this reader is called.
145    * @param is The input stream that is to be read.
146    * @throws IOException if the URL cannot be read.
147    * @throws UnknownCatalogFormatException if the catalog format is
148    * not recognized.
149    * @throws UnparseableCatalogException if the catalog cannot be parsed.
150    * (For example, if it is supposed to be XML and isn't well-formed or
151    * if the parser class cannot be instantiated.)
152    */
153   public void readCatalog(Catalog catalog, InputStream JavaDoc is)
154     throws IOException JavaDoc, CatalogException {
155
156     DocumentBuilderFactory JavaDoc factory = null;
157     DocumentBuilder JavaDoc builder = null;
158
159     factory = DocumentBuilderFactory.newInstance();
160     factory.setNamespaceAware(false);
161     factory.setValidating(false);
162     try {
163       builder = factory.newDocumentBuilder();
164     } catch (ParserConfigurationException JavaDoc pce) {
165       throw new CatalogException(CatalogException.UNPARSEABLE);
166     }
167
168     Document doc = null;
169
170     try {
171       doc = builder.parse(is);
172     } catch (SAXException JavaDoc se) {
173       throw new CatalogException(CatalogException.UNKNOWN_FORMAT);
174     }
175
176     Element root = doc.getDocumentElement();
177
178     String JavaDoc namespaceURI = Namespaces.getNamespaceURI(root);
179     String JavaDoc localName = Namespaces.getLocalName(root);
180
181     String JavaDoc domParserClass = getCatalogParser(namespaceURI,
182                          localName);
183
184     if (domParserClass == null) {
185       if (namespaceURI == null) {
186     catalog.getCatalogManager().debug.message(1, "No Catalog parser for "
187                           + localName);
188       } else {
189     catalog.getCatalogManager().debug.message(1, "No Catalog parser for "
190                           + "{" + namespaceURI + "}"
191                           + localName);
192       }
193       return;
194     }
195
196     DOMCatalogParser domParser = null;
197
198     try {
199       domParser = (DOMCatalogParser) Class.forName(domParserClass).newInstance();
200     } catch (ClassNotFoundException JavaDoc cnfe) {
201       catalog.getCatalogManager().debug.message(1, "Cannot load XML Catalog Parser class", domParserClass);
202       throw new CatalogException(CatalogException.UNPARSEABLE);
203     } catch (InstantiationException JavaDoc ie) {
204       catalog.getCatalogManager().debug.message(1, "Cannot instantiate XML Catalog Parser class", domParserClass);
205       throw new CatalogException(CatalogException.UNPARSEABLE);
206     } catch (IllegalAccessException JavaDoc iae) {
207       catalog.getCatalogManager().debug.message(1, "Cannot access XML Catalog Parser class", domParserClass);
208       throw new CatalogException(CatalogException.UNPARSEABLE);
209     } catch (ClassCastException JavaDoc cce ) {
210       catalog.getCatalogManager().debug.message(1, "Cannot cast XML Catalog Parser class", domParserClass);
211       throw new CatalogException(CatalogException.UNPARSEABLE);
212     }
213
214     Node node = root.getFirstChild();
215     while (node != null) {
216       domParser.parseCatalogEntry(catalog, node);
217       node = node.getNextSibling();
218     }
219   }
220
221   /**
222    * Read the catalog behind the specified URL.
223    *
224    * @see #readCatalog(Catalog, InputStream)
225    *
226    * @param catalog The catalog for which we are reading.
227    * @param fileUrl The URL of the document that should be read.
228    *
229    * @throws MalformedURLException if the specified URL cannot be
230    * turned into a URL object.
231    * @throws IOException if the URL cannot be read.
232    * @throws UnknownCatalogFormatException if the catalog format is
233    * not recognized.
234    * @throws UnparseableCatalogException if the catalog cannot be parsed.
235    * (For example, if it is supposed to be XML and isn't well-formed.)
236    */
237   public void readCatalog(Catalog catalog, String JavaDoc fileUrl)
238     throws MalformedURLException JavaDoc, IOException JavaDoc, CatalogException {
239     URL JavaDoc url = new URL JavaDoc(fileUrl);
240     URLConnection JavaDoc urlCon = url.openConnection();
241     readCatalog(catalog, urlCon.getInputStream());
242   }
243 }
244
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