1 /* 2 * Copyright (C) 2012 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 5 * in compliance with the License. You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software distributed under the License 10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 11 * or implied. See the License for the specific language governing permissions and limitations under 12 * the License. 13 */ 14 15 package com.example.android.networkusage; 16 17 import android.util.Xml; 18 19 import org.xmlpull.v1.XmlPullParser; 20 import org.xmlpull.v1.XmlPullParserException; 21 22 import java.io.IOException; 23 import java.io.InputStream; 24 import java.util.ArrayList; 25 import java.util.List; 26 27 /** 28 * This class parses XML feeds from stackoverflow.com. 29 * Given an InputStream representation of a feed, it returns a List of entries, 30 * where each list element represents a single entry (post) in the XML feed. 31 */ 32 public class StackOverflowXmlParser { 33 private static final String ns = null; 34 35 // We don't use namespaces 36 37 public List<Entry> parse(InputStream in) throws XmlPullParserException, IOException { 38 try { 39 XmlPullParser parser = Xml.newPullParser(); 40 parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false); 41 parser.setInput(in, null); 42 parser.nextTag(); 43 return readFeed(parser); 44 } finally { 45 in.close(); 46 } 47 } 48 49 private List<Entry> readFeed(XmlPullParser parser) throws XmlPullParserException, IOException { 50 List<Entry> entries = new ArrayList<Entry>(); 51 52 parser.require(XmlPullParser.START_TAG, ns, "feed"); 53 while (parser.next() != XmlPullParser.END_TAG) { 54 if (parser.getEventType() != XmlPullParser.START_TAG) { 55 continue; 56 } 57 String name = parser.getName(); 58 // Starts by looking for the entry tag 59 if (name.equals("entry")) { 60 entries.add(readEntry(parser)); 61 } else { 62 skip(parser); 63 } 64 } 65 return entries; 66 } 67 68 // This class represents a single entry (post) in the XML feed. 69 // It includes the data members "title," "link," and "summary." 70 public static class Entry { 71 public final String title; 72 public final String link; 73 public final String summary; 74 75 private Entry(String title, String summary, String link) { 76 this.title = title; 77 this.summary = summary; 78 this.link = link; 79 } 80 } 81 82 // Parses the contents of an entry. If it encounters a title, summary, or link tag, hands them 83 // off 84 // to their respective "read" methods for processing. Otherwise, skips the tag. 85 private Entry readEntry(XmlPullParser parser) throws XmlPullParserException, IOException { 86 parser.require(XmlPullParser.START_TAG, ns, "entry"); 87 String title = null; 88 String summary = null; 89 String link = null; 90 while (parser.next() != XmlPullParser.END_TAG) { 91 if (parser.getEventType() != XmlPullParser.START_TAG) { 92 continue; 93 } 94 String name = parser.getName(); 95 if (name.equals("title")) { 96 title = readTitle(parser); 97 } else if (name.equals("summary")) { 98 summary = readSummary(parser); 99 } else if (name.equals("link")) { 100 link = readLink(parser); 101 } else { 102 skip(parser); 103 } 104 } 105 return new Entry(title, summary, link); 106 } 107 108 // Processes title tags in the feed. 109 private String readTitle(XmlPullParser parser) throws IOException, XmlPullParserException { 110 parser.require(XmlPullParser.START_TAG, ns, "title"); 111 String title = readText(parser); 112 parser.require(XmlPullParser.END_TAG, ns, "title"); 113 return title; 114 } 115 116 // Processes link tags in the feed. 117 private String readLink(XmlPullParser parser) throws IOException, XmlPullParserException { 118 String link = ""; 119 parser.require(XmlPullParser.START_TAG, ns, "link"); 120 String tag = parser.getName(); 121 String relType = parser.getAttributeValue(null, "rel"); 122 if (tag.equals("link")) { 123 if (relType.equals("alternate")) { 124 link = parser.getAttributeValue(null, "href"); 125 parser.nextTag(); 126 } 127 } 128 parser.require(XmlPullParser.END_TAG, ns, "link"); 129 return link; 130 } 131 132 // Processes summary tags in the feed. 133 private String readSummary(XmlPullParser parser) throws IOException, XmlPullParserException { 134 parser.require(XmlPullParser.START_TAG, ns, "summary"); 135 String summary = readText(parser); 136 parser.require(XmlPullParser.END_TAG, ns, "summary"); 137 return summary; 138 } 139 140 // For the tags title and summary, extracts their text values. 141 private String readText(XmlPullParser parser) throws IOException, XmlPullParserException { 142 String result = ""; 143 if (parser.next() == XmlPullParser.TEXT) { 144 result = parser.getText(); 145 parser.nextTag(); 146 } 147 return result; 148 } 149 150 // Skips tags the parser isn't interested in. Uses depth to handle nested tags. i.e., 151 // if the next tag after a START_TAG isn't a matching END_TAG, it keeps going until it 152 // finds the matching END_TAG (as indicated by the value of "depth" being 0). 153 private void skip(XmlPullParser parser) throws XmlPullParserException, IOException { 154 if (parser.getEventType() != XmlPullParser.START_TAG) { 155 throw new IllegalStateException(); 156 } 157 int depth = 1; 158 while (depth != 0) { 159 switch (parser.next()) { 160 case XmlPullParser.END_TAG: 161 depth--; 162 break; 163 case XmlPullParser.START_TAG: 164 depth++; 165 break; 166 } 167 } 168 } 169 } 170
