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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.net.wifi.hotspot2.omadm;
     18 
     19 import org.xml.sax.Attributes;
     20 import org.xml.sax.InputSource;
     21 import org.xml.sax.SAXException;
     22 import org.xml.sax.helpers.DefaultHandler;
     23 
     24 import android.text.TextUtils;
     25 
     26 import java.io.IOException;
     27 import java.io.StringReader;
     28 
     29 import javax.xml.parsers.ParserConfigurationException;
     30 import javax.xml.parsers.SAXParser;
     31 import javax.xml.parsers.SAXParserFactory;
     32 
     33 /**
     34  * Class for parsing an XML string to an XML tree represented by {@link XMLNode}.
     35  *
     36  * The original XML string:
     37  * <root>
     38  *   <tag1>text1</tag1>
     39  *   <tag2>
     40  *     <tag3>text3</tag3>
     41  *   </tag2>
     42  * </root>
     43  *
     44  * The XML tree representation:
     45  *                  [root]
     46  *                     |
     47  *                     |
     48  *   [tag1, text1]-----|-----[tag2]
     49  *                             |
     50  *                             |
     51  *                       [tag3, text3]
     52  *
     53  * @hide
     54  */
     55 public class XMLParser extends DefaultHandler {
     56     private XMLNode mRoot = null;
     57     private XMLNode mCurrent = null;
     58 
     59     public XMLNode parse(String text) throws IOException, SAXException {
     60         if (TextUtils.isEmpty(text)) {
     61             throw new IOException("XML string not provided");
     62         }
     63 
     64         // Reset pointers.
     65         mRoot = null;
     66         mCurrent = null;
     67 
     68         try {
     69             SAXParser parser = SAXParserFactory.newInstance().newSAXParser();
     70             parser.parse(new InputSource(new StringReader(text)), this);
     71             return mRoot;
     72         } catch (ParserConfigurationException pce) {
     73             throw new SAXException(pce);
     74         }
     75     }
     76 
     77     @Override
     78     public void startElement(String uri, String localName, String qName, Attributes attributes)
     79             throws SAXException {
     80         XMLNode parent = mCurrent;
     81 
     82         mCurrent = new XMLNode(parent, qName);
     83 
     84         if (mRoot == null) {
     85             mRoot = mCurrent;
     86         } else if (parent == null) {
     87             throw new SAXException("More than one root nodes");
     88         } else {
     89             parent.addChild(mCurrent);
     90         }
     91     }
     92 
     93     @Override
     94     public void endElement(String uri, String localName, String qName) throws SAXException {
     95         if (!qName.equals(mCurrent.getTag())) {
     96             throw new SAXException("End tag '" + qName + "' doesn't match current node: " +
     97                     mCurrent);
     98         }
     99 
    100         mCurrent.close();
    101         mCurrent = mCurrent.getParent();
    102     }
    103 
    104     @Override
    105     public void characters(char[] ch, int start, int length) throws SAXException {
    106         mCurrent.addText(new String(ch, start, length));
    107     }
    108 }
    109