001 /* $Id: NodeCreateRule.java 729255 2008-12-24 06:58:55Z rahul $ 002 * 003 * Licensed to the Apache Software Foundation (ASF) under one or more 004 * contributor license agreements. See the NOTICE file distributed with 005 * this work for additional information regarding copyright ownership. 006 * The ASF licenses this file to You under the Apache License, Version 2.0 007 * (the "License"); you may not use this file except in compliance with 008 * the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 019 020 package org.apache.commons.digester; 021 022 023 import javax.xml.parsers.DocumentBuilder; 024 import javax.xml.parsers.DocumentBuilderFactory; 025 import javax.xml.parsers.ParserConfigurationException; 026 027 import org.w3c.dom.Attr; 028 import org.w3c.dom.DOMException; 029 import org.w3c.dom.Document; 030 import org.w3c.dom.Element; 031 import org.w3c.dom.Node; 032 import org.xml.sax.Attributes; 033 import org.xml.sax.ContentHandler; 034 import org.xml.sax.SAXException; 035 import org.xml.sax.helpers.DefaultHandler; 036 037 038 /** 039 * A rule implementation that creates a DOM 040 * {@link org.w3c.dom.Node Node} containing the XML at the element that matched 041 * the rule. Two concrete types of nodes can be created by this rule: 042 * <ul> 043 * <li>the default is to create an {@link org.w3c.dom.Element Element} node. 044 * The created element will correspond to the element that matched the rule, 045 * containing all XML content underneath that element.</li> 046 * <li>alternatively, this rule can create nodes of type 047 * {@link org.w3c.dom.DocumentFragment DocumentFragment}, which will contain 048 * only the XML content under the element the rule was trigged on.</li> 049 * </ul> 050 * The created node will be normalized, meaning it will not contain text nodes 051 * that only contain white space characters. 052 * 053 054 * 055 * <p>The created <code>Node</code> will be pushed on Digester's object stack 056 * when done. To use it in the context of another DOM 057 * {@link org.w3c.dom.Document Document}, it must be imported first, using the 058 * Document method 059 * {@link org.w3c.dom.Document#importNode(org.w3c.dom.Node, boolean) importNode()}. 060 * </p> 061 * 062 * <p><strong>Important Note:</strong> This is implemented by replacing the SAX 063 * {@link org.xml.sax.ContentHandler ContentHandler} in the parser used by 064 * Digester, and resetting it when the matched element is closed. As a side 065 * effect, rules that would match XML nodes under the element that matches 066 * a <code>NodeCreateRule</code> will never be triggered by Digester, which 067 * usually is the behavior one would expect.</p> 068 * 069 * <p><strong>Note</strong> that the current implementation does not set the namespace prefixes 070 * in the exported nodes. The (usually more important) namespace URIs are set, 071 * of course.</p> 072 * 073 * @since Digester 1.4 074 */ 075 076 public class NodeCreateRule extends Rule { 077 078 079 // ---------------------------------------------------------- Inner Classes 080 081 082 /** 083 * The SAX content handler that does all the actual work of assembling the 084 * DOM node tree from the SAX events. 085 */ 086 private class NodeBuilder 087 extends DefaultHandler { 088 089 090 // ------------------------------------------------------- Constructors 091 092 093 /** 094 * Constructor. 095 * 096 * <p>Stores the content handler currently used by Digester so it can 097 * be reset when done, and initializes the DOM objects needed to 098 * build the node.</p> 099 * 100 * @param doc the document to use to create nodes 101 * @param root the root node 102 * @throws ParserConfigurationException if the DocumentBuilderFactory 103 * could not be instantiated 104 * @throws SAXException if the XMLReader could not be instantiated by 105 * Digester (should not happen) 106 */ 107 public NodeBuilder(Document doc, Node root) 108 throws ParserConfigurationException, SAXException { 109 110 this.doc = doc; 111 this.root = root; 112 this.top = root; 113 114 oldContentHandler = digester.getCustomContentHandler(); 115 116 } 117 118 119 // ------------------------------------------------- Instance Variables 120 121 122 /** 123 * The content handler used by Digester before it was set to this 124 * content handler. 125 */ 126 protected ContentHandler oldContentHandler = null; 127 128 129 /** 130 * Depth of the current node, relative to the element where the content 131 * handler was put into action. 132 */ 133 protected int depth = 0; 134 135 136 /** 137 * A DOM Document used to create the various Node instances. 138 */ 139 protected Document doc = null; 140 141 142 /** 143 * The DOM node that will be pushed on Digester's stack. 144 */ 145 protected Node root = null; 146 147 148 /** 149 * The current top DOM mode. 150 */ 151 protected Node top = null; 152 153 /** 154 * The text content of the current top DOM node. 155 */ 156 protected StringBuffer topText = new StringBuffer(); 157 158 159 // --------------------------------------------- Helper Methods 160 161 /** 162 * Appends a {@link org.w3c.dom.Text Text} node to the current node 163 * if the content reported by the parser is not purely whitespace. 164 */ 165 private void addTextIfPresent() throws SAXException { 166 if (topText.length() > 0) { 167 String str = topText.toString(); 168 topText.setLength(0); 169 170 if (str.trim().length() > 0) { 171 // The contained text is not *pure* whitespace, so create 172 // a text node to hold it. Note that the "untrimmed" text 173 // is stored in the node. 174 try { 175 top.appendChild(doc.createTextNode(str)); 176 } catch (DOMException e) { 177 throw new SAXException(e.getMessage()); 178 } 179 } 180 } 181 } 182 183 // --------------------------------------------- ContentHandler Methods 184 185 186 /** 187 * Handle notification about text embedded within the current node. 188 * <p> 189 * An xml parser calls this when text is found. We need to ensure that this 190 * text gets attached to the new Node we are creating - except in the case 191 * where the only text in the node is whitespace. 192 * <p> 193 * There is a catch, however. According to the sax specification, a parser 194 * does not need to pass all of the text content of a node in one go; it can 195 * make multiple calls passing part of the data on each call. In particular, 196 * when the body of an element includes xml entity-references, at least some 197 * parsers make a separate call to this method to pass just the entity content. 198 * <p> 199 * In this method, we therefore just append the provided text to a 200 * "current text" buffer. When the element end is found, or a child element 201 * is found then we can check whether we have all-whitespace. See method 202 * addTextIfPresent. 203 * 204 * @param ch the characters from the XML document 205 * @param start the start position in the array 206 * @param length the number of characters to read from the array 207 * @throws SAXException if the DOM implementation throws an exception 208 */ 209 public void characters(char[] ch, int start, int length) 210 throws SAXException { 211 212 topText.append(ch, start, length); 213 } 214 215 216 /** 217 * Checks whether control needs to be returned to Digester. 218 * 219 * @param namespaceURI the namespace URI 220 * @param localName the local name 221 * @param qName the qualified (prefixed) name 222 * @throws SAXException if the DOM implementation throws an exception 223 */ 224 public void endElement(String namespaceURI, String localName, 225 String qName) 226 throws SAXException { 227 228 addTextIfPresent(); 229 230 try { 231 if (depth == 0) { 232 getDigester().setCustomContentHandler(oldContentHandler); 233 getDigester().push(root); 234 getDigester().endElement(namespaceURI, localName, qName); 235 } 236 237 top = top.getParentNode(); 238 depth--; 239 } catch (DOMException e) { 240 throw new SAXException(e.getMessage()); 241 } 242 243 } 244 245 246 /** 247 * Adds a new 248 * {@link org.w3c.dom.ProcessingInstruction ProcessingInstruction} to 249 * the current node. 250 * 251 * @param target the processing instruction target 252 * @param data the processing instruction data, or null if none was 253 * supplied 254 * @throws SAXException if the DOM implementation throws an exception 255 */ 256 public void processingInstruction(String target, String data) 257 throws SAXException { 258 259 try { 260 top.appendChild(doc.createProcessingInstruction(target, data)); 261 } catch (DOMException e) { 262 throw new SAXException(e.getMessage()); 263 } 264 265 } 266 267 268 /** 269 * Adds a new child {@link org.w3c.dom.Element Element} to the current 270 * node. 271 * 272 * @param namespaceURI the namespace URI 273 * @param localName the local name 274 * @param qName the qualified (prefixed) name 275 * @param atts the list of attributes 276 * @throws SAXException if the DOM implementation throws an exception 277 */ 278 public void startElement(String namespaceURI, String localName, 279 String qName, Attributes atts) 280 throws SAXException { 281 282 addTextIfPresent(); 283 284 try { 285 Node previousTop = top; 286 if ((localName == null) || (localName.length() == 0)) { 287 top = doc.createElement(qName); 288 } else { 289 top = doc.createElementNS(namespaceURI, localName); 290 } 291 for (int i = 0; i < atts.getLength(); i++) { 292 Attr attr = null; 293 if ((atts.getLocalName(i) == null) || 294 (atts.getLocalName(i).length() == 0)) { 295 attr = doc.createAttribute(atts.getQName(i)); 296 attr.setNodeValue(atts.getValue(i)); 297 ((Element)top).setAttributeNode(attr); 298 } else { 299 attr = doc.createAttributeNS(atts.getURI(i), 300 atts.getLocalName(i)); 301 attr.setNodeValue(atts.getValue(i)); 302 ((Element)top).setAttributeNodeNS(attr); 303 } 304 } 305 previousTop.appendChild(top); 306 depth++; 307 } catch (DOMException e) { 308 throw new SAXException(e.getMessage()); 309 } 310 311 } 312 313 } 314 315 316 // ----------------------------------------------------------- Constructors 317 318 319 /** 320 * Default constructor. Creates an instance of this rule that will create a 321 * DOM {@link org.w3c.dom.Element Element}. 322 */ 323 public NodeCreateRule() throws ParserConfigurationException { 324 325 this(Node.ELEMENT_NODE); 326 327 } 328 329 330 /** 331 * Constructor. Creates an instance of this rule that will create a DOM 332 * {@link org.w3c.dom.Element Element}, but lets you specify the JAXP 333 * <code>DocumentBuilder</code> that should be used when constructing the 334 * node tree. 335 * 336 * @param documentBuilder the JAXP <code>DocumentBuilder</code> to use 337 */ 338 public NodeCreateRule(DocumentBuilder documentBuilder) { 339 340 this(Node.ELEMENT_NODE, documentBuilder); 341 342 } 343 344 345 /** 346 * Constructor. Creates an instance of this rule that will create either a 347 * DOM {@link org.w3c.dom.Element Element} or a DOM 348 * {@link org.w3c.dom.DocumentFragment DocumentFragment}, depending on the 349 * value of the <code>nodeType</code> parameter. 350 * 351 * @param nodeType the type of node to create, which can be either 352 * {@link org.w3c.dom.Node#ELEMENT_NODE Node.ELEMENT_NODE} or 353 * {@link org.w3c.dom.Node#DOCUMENT_FRAGMENT_NODE Node.DOCUMENT_FRAGMENT_NODE} 354 * @throws IllegalArgumentException if the node type is not supported 355 */ 356 public NodeCreateRule(int nodeType) throws ParserConfigurationException { 357 358 this(nodeType, 359 DocumentBuilderFactory.newInstance().newDocumentBuilder()); 360 361 } 362 363 364 /** 365 * Constructor. Creates an instance of this rule that will create either a 366 * DOM {@link org.w3c.dom.Element Element} or a DOM 367 * {@link org.w3c.dom.DocumentFragment DocumentFragment}, depending on the 368 * value of the <code>nodeType</code> parameter. This constructor lets you 369 * specify the JAXP <code>DocumentBuilder</code> that should be used when 370 * constructing the node tree. 371 * 372 * @param nodeType the type of node to create, which can be either 373 * {@link org.w3c.dom.Node#ELEMENT_NODE Node.ELEMENT_NODE} or 374 * {@link org.w3c.dom.Node#DOCUMENT_FRAGMENT_NODE Node.DOCUMENT_FRAGMENT_NODE} 375 * @param documentBuilder the JAXP <code>DocumentBuilder</code> to use 376 * @throws IllegalArgumentException if the node type is not supported 377 */ 378 public NodeCreateRule(int nodeType, DocumentBuilder documentBuilder) { 379 380 if (!((nodeType == Node.DOCUMENT_FRAGMENT_NODE) || 381 (nodeType == Node.ELEMENT_NODE))) { 382 throw new IllegalArgumentException( 383 "Can only create nodes of type DocumentFragment and Element"); 384 } 385 this.nodeType = nodeType; 386 this.documentBuilder = documentBuilder; 387 388 } 389 390 391 // ----------------------------------------------------- Instance Variables 392 393 394 /** 395 * The JAXP <code>DocumentBuilder</code> to use. 396 */ 397 private DocumentBuilder documentBuilder = null; 398 399 400 /** 401 * The type of the node that should be created. Must be one of the 402 * constants defined in {@link org.w3c.dom.Node Node}, but currently only 403 * {@link org.w3c.dom.Node#ELEMENT_NODE Node.ELEMENT_NODE} and 404 * {@link org.w3c.dom.Node#DOCUMENT_FRAGMENT_NODE Node.DOCUMENT_FRAGMENT_NODE} 405 * are allowed values. 406 */ 407 private int nodeType = Node.ELEMENT_NODE; 408 409 410 // ----------------------------------------------------------- Rule Methods 411 412 413 /** 414 * When this method fires, the digester is told to forward all SAX 415 * ContentHandler events to the builder object, resulting in a DOM being 416 * built instead of normal digester rule-handling occurring. When the 417 * end of the current xml element is encountered, the original content 418 * handler is restored (expected to be NULL, allowing normal Digester 419 * operations to continue). 420 * 421 * @param namespaceURI the namespace URI of the matching element, or an 422 * empty string if the parser is not namespace aware or the element has 423 * no namespace 424 * @param name the local name if the parser is namespace aware, or just 425 * the element name otherwise 426 * @param attributes The attribute list of this element 427 * @throws Exception indicates a JAXP configuration problem 428 */ 429 public void begin(String namespaceURI, String name, Attributes attributes) 430 throws Exception { 431 432 Document doc = documentBuilder.newDocument(); 433 NodeBuilder builder = null; 434 if (nodeType == Node.ELEMENT_NODE) { 435 Element element = null; 436 if (getDigester().getNamespaceAware()) { 437 element = 438 doc.createElementNS(namespaceURI, name); 439 for (int i = 0; i < attributes.getLength(); i++) { 440 element.setAttributeNS(attributes.getURI(i), 441 attributes.getQName(i), 442 attributes.getValue(i)); 443 } 444 } else { 445 element = doc.createElement(name); 446 for (int i = 0; i < attributes.getLength(); i++) { 447 element.setAttribute(attributes.getQName(i), 448 attributes.getValue(i)); 449 } 450 } 451 builder = new NodeBuilder(doc, element); 452 } else { 453 builder = new NodeBuilder(doc, doc.createDocumentFragment()); 454 } 455 // the NodeBuilder constructor has already saved the original 456 // value of the digester's custom content handler (expected to 457 // be null, but we save it just in case). So now we just 458 // need to tell the digester to forward events to the builder. 459 getDigester().setCustomContentHandler(builder); 460 } 461 462 463 /** 464 * Pop the Node off the top of the stack. 465 */ 466 public void end() throws Exception { 467 468 digester.pop(); 469 470 } 471 472 473 }