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1 /*
2  * Copyright 2013 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 com.example.android.basicsyncadapter;
18 
19 import android.accounts.Account;
20 import android.annotation.TargetApi;
21 import android.content.AbstractThreadedSyncAdapter;
22 import android.content.ContentProviderClient;
23 import android.content.ContentProviderOperation;
24 import android.content.ContentResolver;
25 import android.content.Context;
26 import android.content.OperationApplicationException;
27 import android.content.SyncResult;
28 import android.database.Cursor;
29 import android.net.Uri;
30 import android.os.Build;
31 import android.os.Bundle;
32 import android.os.RemoteException;
33 import android.util.Log;
34 
35 import com.example.android.basicsyncadapter.net.FeedParser;
36 import com.example.android.basicsyncadapter.provider.FeedContract;
37 
38 import org.xmlpull.v1.XmlPullParserException;
39 
40 import java.io.IOException;
41 import java.io.InputStream;
42 import java.net.HttpURLConnection;
43 import java.net.MalformedURLException;
44 import java.net.URL;
45 import java.text.ParseException;
46 import java.util.ArrayList;
47 import java.util.HashMap;
48 import java.util.List;
49 
50 /**
51  * Define a sync adapter for the app.
52  *
53  * <p>This class is instantiated in {@link SyncService}, which also binds SyncAdapter to the system.
54  * SyncAdapter should only be initialized in SyncService, never anywhere else.
55  *
56  * <p>The system calls onPerformSync() via an RPC call through the IBinder object supplied by
57  * SyncService.
58  */
59 class SyncAdapter extends AbstractThreadedSyncAdapter {
60     public static final String TAG = "SyncAdapter";
61 
62     /**
63      * URL to fetch content from during a sync.
64      *
65      * <p>This points to the Android Developers Blog. (Side note: We highly recommend reading the
66      * Android Developer Blog to stay up to date on the latest Android platform developments!)
67      */
68     private static final String FEED_URL = "http://android-developers.blogspot.com/atom.xml";
69 
70     /**
71      * Network connection timeout, in milliseconds.
72      */
73     private static final int NET_CONNECT_TIMEOUT_MILLIS = 15000;  // 15 seconds
74 
75     /**
76      * Network read timeout, in milliseconds.
77      */
78     private static final int NET_READ_TIMEOUT_MILLIS = 10000;  // 10 seconds
79 
80     /**
81      * Content resolver, for performing database operations.
82      */
83     private final ContentResolver mContentResolver;
84 
85     /**
86      * Project used when querying content provider. Returns all known fields.
87      */
88     private static final String[] PROJECTION = new String[] {
89             FeedContract.Entry._ID,
90             FeedContract.Entry.COLUMN_NAME_ENTRY_ID,
91             FeedContract.Entry.COLUMN_NAME_TITLE,
92             FeedContract.Entry.COLUMN_NAME_LINK,
93             FeedContract.Entry.COLUMN_NAME_PUBLISHED};
94 
95     // Constants representing column positions from PROJECTION.
96     public static final int COLUMN_ID = 0;
97     public static final int COLUMN_ENTRY_ID = 1;
98     public static final int COLUMN_TITLE = 2;
99     public static final int COLUMN_LINK = 3;
100     public static final int COLUMN_PUBLISHED = 4;
101 
102     /**
103      * Constructor. Obtains handle to content resolver for later use.
104      */
SyncAdapter(Context context, boolean autoInitialize)105     public SyncAdapter(Context context, boolean autoInitialize) {
106         super(context, autoInitialize);
107         mContentResolver = context.getContentResolver();
108     }
109 
110     /**
111      * Constructor. Obtains handle to content resolver for later use.
112      */
113     @TargetApi(Build.VERSION_CODES.HONEYCOMB)
SyncAdapter(Context context, boolean autoInitialize, boolean allowParallelSyncs)114     public SyncAdapter(Context context, boolean autoInitialize, boolean allowParallelSyncs) {
115         super(context, autoInitialize, allowParallelSyncs);
116         mContentResolver = context.getContentResolver();
117     }
118 
119     /**
120      * Called by the Android system in response to a request to run the sync adapter. The work
121      * required to read data from the network, parse it, and store it in the content provider is
122      * done here. Extending AbstractThreadedSyncAdapter ensures that all methods within SyncAdapter
123      * run on a background thread. For this reason, blocking I/O and other long-running tasks can be
124      * run <em>in situ</em>, and you don't have to set up a separate thread for them.
125      .
126      *
127      * <p>This is where we actually perform any work required to perform a sync.
128      * {@link android.content.AbstractThreadedSyncAdapter} guarantees that this will be called on a non-UI thread,
129      * so it is safe to peform blocking I/O here.
130      *
131      * <p>The syncResult argument allows you to pass information back to the method that triggered
132      * the sync.
133      */
134     @Override
onPerformSync(Account account, Bundle extras, String authority, ContentProviderClient provider, SyncResult syncResult)135     public void onPerformSync(Account account, Bundle extras, String authority,
136                               ContentProviderClient provider, SyncResult syncResult) {
137         Log.i(TAG, "Beginning network synchronization");
138         try {
139             final URL location = new URL(FEED_URL);
140             InputStream stream = null;
141 
142             try {
143                 Log.i(TAG, "Streaming data from network: " + location);
144                 stream = downloadUrl(location);
145                 updateLocalFeedData(stream, syncResult);
146                 // Makes sure that the InputStream is closed after the app is
147                 // finished using it.
148             } finally {
149                 if (stream != null) {
150                     stream.close();
151                 }
152             }
153         } catch (MalformedURLException e) {
154             Log.e(TAG, "Feed URL is malformed", e);
155             syncResult.stats.numParseExceptions++;
156             return;
157         } catch (IOException e) {
158             Log.e(TAG, "Error reading from network: " + e.toString());
159             syncResult.stats.numIoExceptions++;
160             return;
161         } catch (XmlPullParserException e) {
162             Log.e(TAG, "Error parsing feed: " + e.toString());
163             syncResult.stats.numParseExceptions++;
164             return;
165         } catch (ParseException e) {
166             Log.e(TAG, "Error parsing feed: " + e.toString());
167             syncResult.stats.numParseExceptions++;
168             return;
169         } catch (RemoteException e) {
170             Log.e(TAG, "Error updating database: " + e.toString());
171             syncResult.databaseError = true;
172             return;
173         } catch (OperationApplicationException e) {
174             Log.e(TAG, "Error updating database: " + e.toString());
175             syncResult.databaseError = true;
176             return;
177         }
178         Log.i(TAG, "Network synchronization complete");
179     }
180 
181     /**
182      * Read XML from an input stream, storing it into the content provider.
183      *
184      * <p>This is where incoming data is persisted, committing the results of a sync. In order to
185      * minimize (expensive) disk operations, we compare incoming data with what's already in our
186      * database, and compute a merge. Only changes (insert/update/delete) will result in a database
187      * write.
188      *
189      * <p>As an additional optimization, we use a batch operation to perform all database writes at
190      * once.
191      *
192      * <p>Merge strategy:
193      * 1. Get cursor to all items in feed<br/>
194      * 2. For each item, check if it's in the incoming data.<br/>
195      *    a. YES: Remove from "incoming" list. Check if data has mutated, if so, perform
196      *            database UPDATE.<br/>
197      *    b. NO: Schedule DELETE from database.<br/>
198      * (At this point, incoming database only contains missing items.)<br/>
199      * 3. For any items remaining in incoming list, ADD to database.
200      */
updateLocalFeedData(final InputStream stream, final SyncResult syncResult)201     public void updateLocalFeedData(final InputStream stream, final SyncResult syncResult)
202             throws IOException, XmlPullParserException, RemoteException,
203             OperationApplicationException, ParseException {
204         final FeedParser feedParser = new FeedParser();
205         final ContentResolver contentResolver = getContext().getContentResolver();
206 
207         Log.i(TAG, "Parsing stream as Atom feed");
208         final List<FeedParser.Entry> entries = feedParser.parse(stream);
209         Log.i(TAG, "Parsing complete. Found " + entries.size() + " entries");
210 
211 
212         ArrayList<ContentProviderOperation> batch = new ArrayList<ContentProviderOperation>();
213 
214         // Build hash table of incoming entries
215         HashMap<String, FeedParser.Entry> entryMap = new HashMap<String, FeedParser.Entry>();
216         for (FeedParser.Entry e : entries) {
217             entryMap.put(e.id, e);
218         }
219 
220         // Get list of all items
221         Log.i(TAG, "Fetching local entries for merge");
222         Uri uri = FeedContract.Entry.CONTENT_URI; // Get all entries
223         Cursor c = contentResolver.query(uri, PROJECTION, null, null, null);
224         assert c != null;
225         Log.i(TAG, "Found " + c.getCount() + " local entries. Computing merge solution...");
226 
227         // Find stale data
228         int id;
229         String entryId;
230         String title;
231         String link;
232         long published;
233         while (c.moveToNext()) {
234             syncResult.stats.numEntries++;
235             id = c.getInt(COLUMN_ID);
236             entryId = c.getString(COLUMN_ENTRY_ID);
237             title = c.getString(COLUMN_TITLE);
238             link = c.getString(COLUMN_LINK);
239             published = c.getLong(COLUMN_PUBLISHED);
240             FeedParser.Entry match = entryMap.get(entryId);
241             if (match != null) {
242                 // Entry exists. Remove from entry map to prevent insert later.
243                 entryMap.remove(entryId);
244                 // Check to see if the entry needs to be updated
245                 Uri existingUri = FeedContract.Entry.CONTENT_URI.buildUpon()
246                         .appendPath(Integer.toString(id)).build();
247                 if ((match.title != null && !match.title.equals(title)) ||
248                         (match.link != null && !match.link.equals(link)) ||
249                         (match.published != published)) {
250                     // Update existing record
251                     Log.i(TAG, "Scheduling update: " + existingUri);
252                     batch.add(ContentProviderOperation.newUpdate(existingUri)
253                             .withValue(FeedContract.Entry.COLUMN_NAME_TITLE, match.title)
254                             .withValue(FeedContract.Entry.COLUMN_NAME_LINK, match.link)
255                             .withValue(FeedContract.Entry.COLUMN_NAME_PUBLISHED, match.published)
256                             .build());
257                     syncResult.stats.numUpdates++;
258                 } else {
259                     Log.i(TAG, "No action: " + existingUri);
260                 }
261             } else {
262                 // Entry doesn't exist. Remove it from the database.
263                 Uri deleteUri = FeedContract.Entry.CONTENT_URI.buildUpon()
264                         .appendPath(Integer.toString(id)).build();
265                 Log.i(TAG, "Scheduling delete: " + deleteUri);
266                 batch.add(ContentProviderOperation.newDelete(deleteUri).build());
267                 syncResult.stats.numDeletes++;
268             }
269         }
270         c.close();
271 
272         // Add new items
273         for (FeedParser.Entry e : entryMap.values()) {
274             Log.i(TAG, "Scheduling insert: entry_id=" + e.id);
275             batch.add(ContentProviderOperation.newInsert(FeedContract.Entry.CONTENT_URI)
276                     .withValue(FeedContract.Entry.COLUMN_NAME_ENTRY_ID, e.id)
277                     .withValue(FeedContract.Entry.COLUMN_NAME_TITLE, e.title)
278                     .withValue(FeedContract.Entry.COLUMN_NAME_LINK, e.link)
279                     .withValue(FeedContract.Entry.COLUMN_NAME_PUBLISHED, e.published)
280                     .build());
281             syncResult.stats.numInserts++;
282         }
283         Log.i(TAG, "Merge solution ready. Applying batch update");
284         mContentResolver.applyBatch(FeedContract.CONTENT_AUTHORITY, batch);
285         mContentResolver.notifyChange(
286                 FeedContract.Entry.CONTENT_URI, // URI where data was modified
287                 null,                           // No local observer
288                 false);                         // IMPORTANT: Do not sync to network
289         // This sample doesn't support uploads, but if *your* code does, make sure you set
290         // syncToNetwork=false in the line above to prevent duplicate syncs.
291     }
292 
293     /**
294      * Given a string representation of a URL, sets up a connection and gets an input stream.
295      */
downloadUrl(final URL url)296     private InputStream downloadUrl(final URL url) throws IOException {
297         HttpURLConnection conn = (HttpURLConnection) url.openConnection();
298         conn.setReadTimeout(NET_READ_TIMEOUT_MILLIS /* milliseconds */);
299         conn.setConnectTimeout(NET_CONNECT_TIMEOUT_MILLIS /* milliseconds */);
300         conn.setRequestMethod("GET");
301         conn.setDoInput(true);
302         // Starts the query
303         conn.connect();
304         return conn.getInputStream();
305     }
306 }
307