Java tutorial
/* Viewer for Khan Academy Copyright (C) 2012 Concentric Sky, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ package com.concentricsky.android.khanacademy.util; import java.io.IOException; import java.io.InputStream; import java.net.SocketTimeoutException; import java.net.URL; import java.net.URLConnection; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import java.util.concurrent.Callable; import org.apache.http.client.ClientProtocolException; import android.webkit.WebResourceResponse; import com.concentricsky.android.khan.R; import com.concentricsky.android.khanacademy.data.KADataService; import com.concentricsky.android.khanacademy.data.db.Caption; import com.fasterxml.jackson.core.JsonParseException; import com.fasterxml.jackson.core.type.TypeReference; import com.fasterxml.jackson.databind.JsonMappingException; import com.fasterxml.jackson.databind.ObjectMapper; import com.j256.ormlite.dao.Dao; import com.j256.ormlite.stmt.QueryBuilder; /** * Handles retrieving subtitles from the web, caching them, and returning them to the video fragment. * * @author austinlally * */ public class CaptionManager { /* *********************** STATIC ***************************/ public static final String LOG_TAG = CaptionManager.class.getSimpleName(); public static final int CONNECT_TIMEOUT = 5000; /* *********************** PRIVATE ***************************/ private KADataService dataService; private String subtitleFormat; /* *********************** PUBLIC ***************************/ /** * Get a CaptionManager to manage your captions! * * @param context Any context will do. Used to look up a string resource, and no reference is kept. */ public CaptionManager(KADataService dataService) { this.dataService = dataService; subtitleFormat = dataService.getString(R.string.url_format_subtitles); } /** * Get a {@link WebResourceResponse} with subtitles for the video with the given youtube id. * * The response contains a UTF-8 encoded json object with the subtitles received * from universalsubtitles.org. * * @param youtubeId The youtube id of the video whose subtitles we need. * @return The {@link WebResourceResponse} with the subtitles, or {@code null} in case of error or if none are found. */ public WebResourceResponse fetchRawCaptionResponse(String youtubeId) { Log.d(LOG_TAG, "fetchRawCaptionResponse"); String youtube_url = "http://www.youtube.com/watch?v=" + youtubeId; try { URL url = new URL(String.format(subtitleFormat, youtube_url, "en")); URLConnection connection = url.openConnection(); connection.setConnectTimeout(CONNECT_TIMEOUT); connection.setUseCaches(true); InputStream in = null; try { in = connection.getInputStream(); } catch (SocketTimeoutException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); //various exceptions including at least ConnectException and UnknownHostException can happen if we're offline } return in == null ? null : new WebResourceResponse("application/json", "UTF-8", in); } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return null; } public List<Caption> getCaptions(String youtubeId) { Log.d(LOG_TAG, "getCaptions: " + youtubeId); List<Caption> result = null; Dao<Caption, Integer> captionDao = null; try { captionDao = dataService.getHelper().getDao(Caption.class); QueryBuilder<Caption, Integer> q = captionDao.queryBuilder(); q.where().eq("youtube_id", youtubeId); q.orderBy("sub_order", true); // TODO : Avoid inserting duplicates in the first place, and do a migration to clean up. q.groupBy("sub_order"); result = q.query(); } catch (SQLException e) { e.printStackTrace(); } if (result != null && result.size() > 0) { Log.d(LOG_TAG, " already cached; returning"); return result; } // If we do not already have the captions, try fetching them. // Clients will call this in a background thread, so we can take our time. WebResourceResponse response = fetchRawCaptionResponse(youtubeId); result = parseAPIResponse(response); result = pruneEmptyCaptions(result); result = persist(result, youtubeId); return result; } private List<Caption> parseAPIResponse(WebResourceResponse response) { Log.d(LOG_TAG, "parseAPIResponse"); List<Caption> result = null; if (response != null) { ObjectMapper mapper = new ObjectMapper(); try { result = mapper.readValue(response.getData(), new TypeReference<List<Caption>>() { }); Log.d(LOG_TAG, " result length is " + result.size()); } catch (JsonParseException e) { // At 5pm on a Thursday, I encountered this exception. Did a little digging, and the response turned // out to contain this: // <html> <body> <div style="text-align: center; padding-top: 200px"> // Amara is currently unavailable for scheduled maintenance. The site will be back shortly. // </div> </body> </html> // Another at 2:45 Tuesday: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens // This has happened more than once around the same time. Caught it again today, Tue 12/4, at about 3:00. // At any rate, these all fall into the "failed to download" category rather than the "none exist" category. e.printStackTrace(); } catch (JsonMappingException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } else { Log.d(LOG_TAG, " response was null"); } return result; } private List<Caption> pruneEmptyCaptions(List<Caption> toPrune) { Log.d(LOG_TAG, "pruneEmptyCaptions"); // Ensure captions have times. See long comment below for explanation. // Otherwise, return null and pretend there were no captions. List<Caption> result = null; if (toPrune != null) { for (Caption c : toPrune) { // Log.d(LOG_TAG, String.format("%03.2f %10d %s", c.getSub_order(), c.getStart_time(), c.getText())); if (c.getStart_time() > 0) { result = toPrune; break; } } } // prune individual empty captions if (result != null && result.size() > 0) { List<Caption> toRemove = new ArrayList<Caption>(); for (Caption caption : result) { if (caption.getText().trim().length() == 0) { toRemove.add(caption); } } for (Caption caption : toRemove) { result.remove(caption); } } return result; } private List<Caption> persist(final List<Caption> toSave, final String youtubeId) { try { final Dao<Caption, Integer> captionDao = dataService.getHelper().getDao(Caption.class); if (captionDao != null && toSave != null && toSave.size() > 0) { // Batching speeds this up significantly. captionDao.callBatchTasks(new Callable<Void>() { @Override public Void call() throws Exception { for (Caption c : toSave) { try { c.setYoutube_id(youtubeId); captionDao.create(c); } catch (SQLException e) { e.printStackTrace(); } } return null; } }); } } catch (SQLException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } return toSave; } /* Example of a response that isn't quite what we want. * In these cases, we just pretend there are no subtitles at all, as an incomplete list without time stamps isn't that useful. * [ { "subtitle_id": "wcpvewparc82371936", "text": "What I want to do in this video is show you that some of the things that we've been talking about ", "start_time": -1, "end_time": -1, "sub_order": 1.0, "start_of_paragraph": false }, { "subtitle_id": "ivddkbpjit82695805", "text": "on the last few videos actually do happen, and in particular,", "start_time": -1, "end_time": -1, "sub_order": 2.0, "start_of_paragraph": false }, { "subtitle_id": "avfjvqzffm83421791", "text": "talk about how one of these speculative attacks on a currency can turn into", "start_time": -1, "end_time": -1, "sub_order": 3.0, "start_of_paragraph": false }, { "subtitle_id": "fmfcpugiut83483196", "text": "a banking crisis! This is a chart", "start_time": -1, "end_time": -1, "sub_order": 4.0, "start_of_paragraph": false }, { "subtitle_id": "otacwxlpyh83540836", "text": "from Oxford Economics, and it shows two things:", "start_time": -1, "end_time": -1, "sub_order": 5.0, "start_of_paragraph": false }, { "subtitle_id": "yyqivgduxz83628118", "text": "Thailand's exchange rate and short-term interest rates from the early", "start_time": -1, "end_time": -1, "sub_order": 6.0, "start_of_paragraph": false }, { "subtitle_id": "rtbbbazapm83760974", "text": "1990's to the present, there's a couple of interesting", "start_time": -1, "end_time": -1, "sub_order": 7.0, "start_of_paragraph": false }, { "subtitle_id": "ccxmomlhbe83829991", "text": "things that you might see over here; the first is the exchange rate, you see", "start_time": -1, "end_time": -1, "sub_order": 8.0, "start_of_paragraph": false } ] */ }