Katie McCormick | 2f8cc17 | 2012-03-16 17:47:55 -0700 | [diff] [blame] | 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 | } |