src/main/java/org/xerial/util/xml/XMLStreamReader.java

   1 /*--------------------------------------------------------------------------\r
   2  *  Copyright 2009 Taro L. Saito\r
   3  *\r
   4  *  Licensed under the Apache License, Version 2.0 (the "License");\r
   5  *  you may not use this file except in compliance with the License.\r
   6  *  You may obtain a copy of the License at\r
   7  *\r
   8  *     http://www.apache.org/licenses/LICENSE-2.0\r
   9  *\r
  10  *  Unless required by applicable law or agreed to in writing, software\r
  11  *  distributed under the License is distributed on an "AS IS" BASIS,\r
  12  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
  13  *  See the License for the specific language governing permissions and\r
  14  *  limitations under the License.\r
  15  *--------------------------------------------------------------------------*/\r
  16 //--------------------------------------\r
  17 // XerialJ\r
  18 //\r
  19 // XMLStreamWalker.java\r
  20 // Since: Mar 30, 2009 5:27:15 PM\r
  21 //\r
  22 // $URL: http://www.xerial.org/svn/project/XerialJ/trunk/xerial-core/src/main/java/org/xerial/util/xml/XMLStreamReader.java $\r
  23 // $Author: leo $\r
  24 //--------------------------------------\r
  25 package org.xerial.util.xml;\r
  26 \r
  27 import static org.xmlpull.v1.XmlPullParser.*;\r
  28 \r
  29 import java.io.IOException;\r
  30 import java.io.Reader;\r
  31 \r
  32 import org.xerial.core.XerialErrorCode;\r
  33 import org.xerial.core.XerialException;\r
  34 import org.xerial.util.ArrayDeque;\r
  35 import org.xerial.util.Deque;\r
  36 import org.xerial.util.tree.TreeEvent;\r
  37 import org.xerial.util.tree.TreeStreamReader;\r
  38 import org.xerial.util.tree.TreeEvent.EventType;\r
  39 import org.xerial.util.xml.impl.TreeEventQueue;\r
  40 import org.xerial.util.xml.pullparser.PullParserUtil;\r
  41 import org.xmlpull.v1.XmlPullParser;\r
  42 import org.xmlpull.v1.XmlPullParserException;\r
  43 \r
  44 /**\r
  45  * {@link TreeStreamReader} of XML data\r
  46  * \r
  47  * @author leo\r
  48  * \r
  49  */\r
  50 public class XMLStreamReader implements TreeStreamReader\r
  51 {\r
  52     private final XmlPullParser pullParser;\r
  53     private final Deque<StringBuilder> textStack = new ArrayDeque<StringBuilder>();\r
  54     private final static StringBuilder EMPTY_STRING = new StringBuilder(0);\r
  55     private int TEXT_BUFFER_MAX = 8192;\r
  56 \r
  57     private int parseState = START_DOCUMENT;\r
  58     private boolean convertValueAttribute = false;\r
  59 \r
  60     private final TreeEventQueue eventQueue = new TreeEventQueue();\r
  61 \r
  62     public XMLStreamReader(Reader reader)\r
  63     {\r
  64         if (reader == null)\r
  65             throw new IllegalArgumentException("XML reader is null");\r
  66 \r
  67         pullParser = PullParserUtil.newParser(reader);\r
  68 \r
  69     }\r
  70 \r
  71     public void useValueAttributeAsNodeValue(boolean enable)\r
  72     {\r
  73         this.convertValueAttribute = enable;\r
  74     }\r
  75 \r
  76     public TreeEvent peekNext() throws XerialException\r
  77     {\r
  78         if (!eventQueue.isEmpty())\r
  79         {\r
  80             return eventQueue.peekFirst();\r
  81         }\r
  82 \r
  83         if (parseState == END_DOCUMENT)\r
  84             return null;\r
  85 \r
  86         readNext();\r
  87 \r
  88         return peekNext();\r
  89     }\r
  90 \r
  91     public TreeEvent next() throws XerialException\r
  92     {\r
  93         if (!eventQueue.isEmpty())\r
  94         {\r
  95             return eventQueue.pop();\r
  96         }\r
  97 \r
  98         if (parseState == END_DOCUMENT)\r
  99             return null;\r
 100 \r
 101         readNext();\r
 102 \r
 103         return next();\r
 104     }\r
 105 \r
 106     public void readNext() throws XerialException\r
 107     {\r
 108         if (parseState == END_DOCUMENT)\r
 109             return;\r
 110 \r
 111         try\r
 112         {\r
 113             parseState = pullParser.next();\r
 114 \r
 115             switch (parseState)\r
 116             {\r
 117             case START_TAG:\r
 118             {\r
 119                 textStack.addLast(EMPTY_STRING);\r
 120                 String tagName = pullParser.getName();\r
 121                 String immediateNodeValue = null;\r
 122 \r
 123                 Deque<TreeEvent> startEventQueue = new ArrayDeque<TreeEvent>(pullParser.getAttributeCount() + 1);\r
 124                 // read attributes\r
 125                 for (int i = 0; i < pullParser.getAttributeCount(); i++)\r
 126                 {\r
 127                     String attributeName = pullParser.getAttributeName(i);\r
 128                     String attributeValue = pullParser.getAttributeValue(i);\r
 129 \r
 130                     // assign the value attribute as a node value of the start tag \r
 131                     if (convertValueAttribute && attributeName.equals("value"))\r
 132                     {\r
 133                         immediateNodeValue = attributeValue;\r
 134                         continue;\r
 135                     }\r
 136 \r
 137                     startEventQueue.addLast(TreeEvent.newVisitEvent(attributeName, attributeValue));\r
 138                     startEventQueue.addLast(TreeEvent.newLeaveEvent(attributeName));\r
 139                 }\r
 140 \r
 141                 // push a new start tag event to the front of the queue\r
 142                 startEventQueue.addFirst(TreeEvent.newVisitEvent(tagName, immediateNodeValue));\r
 143                 eventQueue.push(startEventQueue);\r
 144 \r
 145                 // pre-fetch the next event\r
 146                 readNext();\r
 147             }\r
 148                 break;\r
 149             case END_TAG:\r
 150             {\r
 151                 if (textStack.getLast() == EMPTY_STRING)\r
 152                 {\r
 153                     eventQueue.push(TreeEvent.newLeaveEvent(pullParser.getName()));\r
 154                 }\r
 155                 else\r
 156                 {\r
 157                     StringBuilder textBuffer = textStack.getLast();\r
 158                     if (!eventQueue.isEmpty() && eventQueue.peekLast().event == EventType.VISIT)\r
 159                     {\r
 160                         // attach the text value to the the previous visit event\r
 161                         eventQueue.replaceLast(TreeEvent.newVisitEvent(pullParser.getName(), sanitize(textBuffer\r
 162                                 .toString())));\r
 163                     }\r
 164                     else\r
 165                         reportTextEvent(textBuffer);\r
 166 \r
 167                     eventQueue.push(TreeEvent.newLeaveEvent(pullParser.getName()));\r
 168                 }\r
 169                 textStack.removeLast();\r
 170             }\r
 171                 break;\r
 172             case TEXT:\r
 173             {\r
 174                 String textData = pullParser.getText();\r
 175                 StringBuilder textBuffer = textStack.getLast();\r
 176 \r
 177                 if (textData.length() <= 0)\r
 178                     break;\r
 179 \r
 180                 if (textBuffer == EMPTY_STRING)\r
 181                 {\r
 182                     textBuffer = replaceLastTextBuffer();\r
 183                 }\r
 184                 else if (textBuffer.length() + textData.length() > TEXT_BUFFER_MAX)\r
 185                 {\r
 186                     // add the previous text data to the event queue\r
 187                     reportTextEvent(textBuffer);\r
 188 \r
 189                     // replace the text buffer\r
 190                     textBuffer = replaceLastTextBuffer();\r
 191                 }\r
 192                 textBuffer.append(textData);\r
 193 \r
 194                 boolean needPrefetch = eventQueue.isEmpty() ? false : eventQueue.peekLast().event == EventType.VISIT;\r
 195                 if (needPrefetch)\r
 196                     readNext();\r
 197             }\r
 198                 break;\r
 199             default:\r
 200                 // do nothing\r
 201                 break;\r
 202             }\r
 203 \r
 204         }\r
 205         catch (XmlPullParserException e)\r
 206         {\r
 207             throw new XerialException(XMLErrorCode.PARSE_ERROR, e);\r
 208         }\r
 209         catch (IOException e)\r
 210         {\r
 211             throw new XerialException(XerialErrorCode.IO_EXCEPTION, e);\r
 212         }\r
 213 \r
 214     }\r
 215 \r
 216     private StringBuilder replaceLastTextBuffer()\r
 217     {\r
 218         textStack.removeLast();\r
 219         StringBuilder textBuffer = new StringBuilder();\r
 220         textStack.addLast(textBuffer);\r
 221         return textBuffer;\r
 222     }\r
 223 \r
 224     private String sanitize(String s)\r
 225     {\r
 226         return s.trim();\r
 227     }\r
 228 \r
 229     private void reportTextEvent(StringBuilder buffer)\r
 230     {\r
 231         reportTextEvent(buffer.toString());\r
 232     }\r
 233 \r
 234     private void reportTextEvent(String textData)\r
 235     {\r
 236         textData = sanitize(textData);\r
 237 \r
 238         if (textData.length() > 0)\r
 239             eventQueue.push(TreeEvent.newTextEvent(eventQueue.getContextNodeName(), textData));\r
 240     }\r
 241 \r
 242 }\r