1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.jxpath.xml;
18
19 import java.io.IOException;
20 import java.io.InputStream;
21 import java.net.URL;
22 import java.util.HashMap;
23
24 import org.apache.commons.jxpath.Container;
25 import org.apache.commons.jxpath.JXPathException;
26 import org.apache.commons.jxpath.util.ClassLoaderUtil;
27
28 /**
29 * An XML document container reads and parses XML only when it is
30 * accessed. JXPath traverses Containers transparently -
31 * you use the same paths to access objects in containers as you
32 * do to access those objects directly. You can create
33 * XMLDocumentContainers for various XML documents that may or
34 * may not be accessed by XPaths. If they are, they will be automatically
35 * read, parsed and traversed. If they are not - they won't be
36 * read at all.
37 *
38 * @author Dmitri Plotnikov
39 * @version $Revision: 916559 $ $Date: 2010-02-26 04:55:46 +0100 (Fr, 26 Feb 2010) $
40 */
41 public class DocumentContainer extends XMLParser2 implements Container {
42
43 /** DOM constant */
44 public static final String MODEL_DOM = "DOM";
45
46 /** JDOM constant */
47 public static final String MODEL_JDOM = "JDOM";
48
49 private static final long serialVersionUID = -8713290334113427066L;
50
51 private static HashMap parserClasses = new HashMap();
52 static {
53 parserClasses.put(MODEL_DOM,
54 "org.apache.commons.jxpath.xml.DOMParser");
55 parserClasses.put(MODEL_JDOM,
56 "org.apache.commons.jxpath.xml.JDOMParser");
57 }
58
59 private static HashMap parsers = new HashMap();
60
61 private Object document;
62 private URL xmlURL;
63 private String model;
64
65 /**
66 * Add an XML parser. Parsers for the models "DOM" and "JDOM" are
67 * pre-registered.
68 * @param model model name
69 * @param parser parser
70 */
71 public static void registerXMLParser(String model, XMLParser parser) {
72 parsers.put(model, parser);
73 }
74
75 /**
76 * Add a class of a custom XML parser.
77 * Parsers for the models "DOM" and "JDOM" are pre-registered.
78 * @param model model name
79 * @param parserClassName parser classname
80 */
81 public static void registerXMLParser(String model, String parserClassName) {
82 parserClasses.put(model, parserClassName);
83 }
84
85 /**
86 * Use this constructor if the desired model is DOM.
87 *
88 * @param xmlURL is a URL for an XML file.
89 * Use getClass().getResource(resourceName) to load XML from a
90 * resource file.
91 */
92 public DocumentContainer(URL xmlURL) {
93 this(xmlURL, MODEL_DOM);
94 }
95
96 /**
97 * Construct a new DocumentContainer.
98 * @param xmlURL is a URL for an XML file. Use getClass().getResource
99 * (resourceName) to load XML from a resource file.
100 *
101 * @param model is one of the MODEL_* constants defined in this class. It
102 * determines which parser should be used to load the XML.
103 */
104 public DocumentContainer(URL xmlURL, String model) {
105 this.xmlURL = xmlURL;
106 if (xmlURL == null) {
107 throw new JXPathException("XML URL is null");
108 }
109 this.model = model;
110 }
111
112 /**
113 * Reads XML, caches it internally and returns the Document.
114 * @return Object
115 */
116 public Object getValue() {
117 if (document == null) {
118 try {
119 InputStream stream = null;
120 try {
121 if (xmlURL != null) {
122 stream = xmlURL.openStream();
123 }
124 document = parseXML(stream);
125 }
126 finally {
127 if (stream != null) {
128 stream.close();
129 }
130 }
131 }
132 catch (IOException ex) {
133 throw new JXPathException(
134 "Cannot read XML from: " + xmlURL.toString(),
135 ex);
136 }
137 }
138 return document;
139 }
140
141 /**
142 * Parses XML using the parser for the specified model.
143 * @param stream InputStream
144 * @return Object
145 */
146 public Object parseXML(InputStream stream) {
147 XMLParser parser = getParser(model);
148 if (parser instanceof XMLParser2) {
149 XMLParser2 parser2 = (XMLParser2) parser;
150 parser2.setValidating(isValidating());
151 parser2.setNamespaceAware(isNamespaceAware());
152 parser2.setIgnoringElementContentWhitespace(
153 isIgnoringElementContentWhitespace());
154 parser2.setExpandEntityReferences(isExpandEntityReferences());
155 parser2.setIgnoringComments(isIgnoringComments());
156 parser2.setCoalescing(isCoalescing());
157 }
158 return parser.parseXML(stream);
159 }
160
161 /**
162 * Throws an UnsupportedOperationException.
163 * @param value value (not) to set
164 */
165 public void setValue(Object value) {
166 throw new UnsupportedOperationException();
167 }
168
169 /**
170 * Maps a model type to a parser.
171 * @param model input model type
172 * @return XMLParser
173 */
174 private static XMLParser getParser(String model) {
175 XMLParser parser = (XMLParser) parsers.get(model);
176 if (parser == null) {
177 String className = (String) parserClasses.get(model);
178 if (className == null) {
179 throw new JXPathException("Unsupported XML model: " + model);
180 }
181 try {
182 Class clazz = ClassLoaderUtil.getClass(className, true);
183 parser = (XMLParser) clazz.newInstance();
184 }
185 catch (Exception ex) {
186 throw new JXPathException(
187 "Cannot allocate XMLParser: " + className, ex);
188 }
189 parsers.put(model, parser);
190 }
191 return parser;
192 }
193 }