Java tutorial
/* * Copyright (C) 2011 - 2012 Niall 'Rivernile' Scott * * This software is provided 'as-is', without any express or implied * warranty. In no event will the authors or contributors be held liable for * any damages arising from the use of this software. * * The aforementioned copyright holder(s) hereby grant you a * non-transferrable right to use this software for any purpose (including * commercial applications), and to modify it and redistribute it, subject to * the following conditions: * * 1. This notice may not be removed or altered from any file it appears in. * * 2. Any modifications made to this software, except those defined in * clause 3 of this agreement, must be released under this license, and * the source code of any modifications must be made available on a * publically accessible (and locateable) website, or sent to the * original author of this software. * * 3. Software modifications that do not alter the functionality of the * software but are simply adaptations to a specific environment are * exempt from clause 2. */ package uk.org.rivernile.edinburghbustracker.android.livetimes.parser; import java.io.BufferedInputStream; import java.io.IOException; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.util.HashMap; import java.util.Random; import org.json.JSONArray; import org.json.JSONException; import org.json.JSONObject; import uk.org.rivernile.android.bustracker.parser.livetimes.BusParser; import uk.org.rivernile.android.bustracker.parser.livetimes.BusParserException; import uk.org.rivernile.android.bustracker.parser.livetimes.BusStop; import uk.org.rivernile.edinburghbustracker.android.ApiKey; /** * This is the Edinburgh specific implementation of the bus times parser. To * get an instance of this class, call EdinburghParser.getInstance() * * @author Niall Scott */ public final class EdinburghParser implements BusParser { /** This error is called when an invalid key has been specified. */ public static final byte ERROR_INVALID_APP_KEY = 7; /** This error is called when an invalid parameter has been specified. */ public static final byte ERROR_INVALID_PARAMETER = 8; /** This error is called when the system encounters a processing error. */ public static final byte ERROR_PROCESSING_ERROR = 9; /** This error is called when the system is under maintenance. */ public static final byte ERROR_SYSTEM_MAINTENANCE = 10; /** This error is called when the system is overloaded. */ public static final byte ERROR_SYSTEM_OVERLOADED = 11; private static final String URL = "http://www.mybustracker.co.uk/ws.php?module=json&key="; private static final Random rand = new Random(System.currentTimeMillis()); private boolean globalDisruption = false; /** * Create a new EdinburghParser object. */ public EdinburghParser() { // Nothing to do here. } /** * {@inheritDoc} */ @Override public HashMap<String, BusStop> getBusStopData(final String[] stopCodes, final int numDepartures) throws BusParserException { if (stopCodes == null || stopCodes.length == 0) return null; // Build the URL. final StringBuilder sb = new StringBuilder(); sb.append(URL); sb.append(ApiKey.getHashedKey()); sb.append("&function=getBusTimes&"); final int len = stopCodes.length; if (len == 1) { sb.append("stopId="); sb.append(stopCodes[0]); sb.append('&'); } else { for (int i = 0; i < len; i++) { if (i >= 6) break; sb.append("stopId"); sb.append(i + 1); sb.append('='); sb.append(stopCodes[i]); sb.append('&'); } } sb.append("nb="); sb.append(numDepartures); // Add a random arg so the response isn't cached by the network proxies. sb.append("&random="); sb.append(rand.nextInt()); // TODO: review this code. I'm sure it could be done better. try { final URL url = new URL(sb.toString()); // Reset the StringBuilder because we're going to reuse it. sb.setLength(0); final HttpURLConnection conn = (HttpURLConnection) url.openConnection(); try { final BufferedInputStream is = new BufferedInputStream(conn.getInputStream()); // Check to see if the URL we connected to was what we expected. if (!url.getHost().equals(conn.getURL().getHost())) { is.close(); conn.disconnect(); throw new BusParserException(ERROR_URLMISMATCH); } int data; while ((data = is.read()) != -1) { sb.append((char) data); } } finally { conn.disconnect(); } return parseJSON(sb.toString()); } catch (MalformedURLException e) { throw new BusParserException(ERROR_CANNOTRESOLVE); } catch (IOException e) { throw new BusParserException(ERROR_NOCONNECTION); } catch (JSONException e) { throw new BusParserException(ERROR_PARSEERR); } } /** * Parse the JSON string returned from the bus tracker web services. * * @param jsonString The JSON string to parse. * @return A HashMap which has String -> BusStop mappings containing the * bus stop data. * @throws JSONException When a JSON exception occurs. * @throws BusParserException When a BusParserException occurs. */ private HashMap<String, BusStop> parseJSON(final String jsonString) throws JSONException, BusParserException { final HashMap<String, BusStop> data = new HashMap<String, BusStop>(); JSONObject jo = new JSONObject(jsonString); // Check to see if the API returns errors. if (jo.has("faultcode")) { final String err = jo.getString("faultcode"); if ("INVALID_APP_KEY".equals(err)) { throw new BusParserException(ERROR_INVALID_APP_KEY); } else if ("INVALID_PARAMETER".equals(err)) { throw new BusParserException(ERROR_INVALID_PARAMETER); } else if ("PROCESSING_ERROR".equals(err)) { throw new BusParserException(ERROR_PROCESSING_ERROR); } else if ("SYSTEM_MAINTENANCE".equals(err)) { throw new BusParserException(ERROR_SYSTEM_MAINTENANCE); } else if ("SYSTEM_OVERLOADED".equals(err)) { throw new BusParserException(ERROR_SYSTEM_OVERLOADED); } else { throw new BusParserException(ERROR_UNKNOWN); } } final JSONArray ja = jo.getJSONArray("busTimes"); EdinburghBusStop currentBusStop; EdinburghBusService currentBusService; // Make sure there's array elements. final int len = ja.length(); if (len == 0) { throw new BusParserException(ERROR_NODATA); } String temp; for (int i = 0; i < len; i++) { jo = ja.getJSONObject(i); // Check to see if there are any global disruptions. globalDisruption = jo.getBoolean("globalDisruption"); temp = jo.getString("stopId"); // Get data for the bus stop. currentBusStop = (EdinburghBusStop) data.get(temp); if (currentBusStop == null) { currentBusStop = parseEdinburghBusStop(jo); if (currentBusStop != null) { data.put(temp, currentBusStop); } else { continue; } } // Add a bus service to the current bus stop. currentBusService = parseEdinburghBusService(jo); if (currentBusService != null) { currentBusStop.addBusService(currentBusService); } } return data; } /** * Create an EdinburghBusStop object from a JSONObject. * * @param joStop The JSONObject to parse. * @return An EdinburghBusStop object, or null if there was a problem. */ private static EdinburghBusStop parseEdinburghBusStop(final JSONObject joStop) { try { return new EdinburghBusStop(joStop.getString("stopId"), joStop.getString("stopName"), joStop.getBoolean("busStopDisruption")); } catch (JSONException e) { // Nothing to do. } catch (IllegalArgumentException e) { // Nothing to do. } return null; } /** * Create an EdinburghBus object from a JSONObject. * * @param joService The JSONObject to parse. * @return An EdinburghBusService object, or null if there was a problem. */ private static EdinburghBusService parseEdinburghBusService(final JSONObject joService) { try { final EdinburghBusService service = new EdinburghBusService(joService.getString("mnemoService"), joService.getString("nameService"), joService.getBoolean("serviceDisruption")); final JSONArray jaBuses = joService.getJSONArray("timeDatas"); final int len = jaBuses.length(); EdinburghBus currentBus; // Loop through the times for each bus. for (int i = 0; i < len; i++) { currentBus = parseEdinburghBus(jaBuses.getJSONObject(i)); if (currentBus != null) { service.addBus(currentBus); } } return service; } catch (JSONException e) { // Nothing to do. } catch (IllegalArgumentException e) { // Nothing to do. } return null; } /** * Create an EdinburghBus object from a JSONObject. * * @param joBus The JSONObject to parse. * @return An EdinburghBus object, or null if there was a problem. */ private static EdinburghBus parseEdinburghBus(final JSONObject joBus) { try { final char reliability = joBus.getString("reliability").charAt(0); final char type = joBus.getString("type").charAt(0); return new EdinburghBus(joBus.getString("nameDest"), joBus.getInt("day"), joBus.getString("time"), joBus.getInt("minutes"), reliability, type, joBus.getString("terminus")); } catch (JSONException e) { // Nothing to do. } catch (IllegalArgumentException e) { // Nothing to do. } return null; } /** * Get the global disruption status. * * @return The global disruption status. */ public boolean getGlobalDisruption() { return globalDisruption; } }