Java tutorial
/* * SMART FP7 - Search engine for MultimediA enviRonment generated contenT * Webpage: http://smartfp7.eu * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. * * The Original Code is Copyright (c) 2012-2013 Athens Information Technology * All Rights Reserved * * Contributor: * Nikolaos Katsarakis nkat@ait.edu.gr */ package eu.smartfp7.EdgeNode; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.PrintWriter; import java.io.UnsupportedEncodingException; import java.util.Calendar; import java.util.GregorianCalendar; import java.util.HashMap; import java.util.List; import java.util.Map.Entry; import java.util.Properties; import java.util.TimeZone; import java.util.Timer; import java.util.TimerTask; import javax.servlet.Servlet; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.lightcouch.CouchDbClient; import com.google.gson.JsonElement; import com.google.gson.JsonObject; /** * Servlet implementation class ReplayFeed */ @WebServlet(name = "replayFeed", description = "Simulates a live feed", urlPatterns = { "/replayFeed" }) public class ReplayFeed extends HttpServlet { private static final long serialVersionUID = 1L; // CouchDB access parameters private CouchDbClient feedsClient = null; private String server, user, pass; private int port; // HashMap<String, Timer> timerList = null; // HashMap<String, CouchDbClient> dbClientList = null; // HashMap<String, Integer> dbClientUsage = null; HashMap<String, ReplayTaskData> replayList = null; Calendar cal; // Used for printing dates /** * @see HttpServlet#HttpServlet() */ public ReplayFeed() { super(); } /** * @see Servlet#init(ServletConfig) */ public void init(ServletConfig config) throws ServletException { try { super.init(config); } catch (ServletException e) { System.err.println("Can not initialize servlet"); return; } // Read couchdb properties from file and initialise the client for feeds Properties dbProps = new Properties(); try { dbProps.load(getServletContext().getResourceAsStream("/WEB-INF/couchdb.properties")); } catch (IOException e1) { System.err.println("Can not open couchdb properties file"); return; } server = dbProps.getProperty("server"); port = Integer.parseInt(dbProps.getProperty("port")); user = dbProps.getProperty("user"); pass = dbProps.getProperty("pass"); // Test for incorrect user/pass or CouchDB server offline try { feedsClient = new CouchDbClient("feeds", true, "http", server, port, user, pass); } catch (Exception e) { System.out.println( "Could not connect to CouchDB, check that the server is running and that the correct username/pass is set"); System.out.println("Current configuration: server=" + server + ", port=" + port + ", user= " + user + ", pass= " + pass); return; } // timerList = new HashMap<String, Timer>(); // dbClientList = new HashMap<String, CouchDbClient>(); // dbClientUsage = new HashMap<String, Integer>(); replayList = new HashMap<String, ReplayTaskData>(); cal = new GregorianCalendar(TimeZone.getTimeZone("UTC")); } /** * @see Servlet#destroy() */ public void destroy() { // Stop all running timers cancelTimers(); // Close feeds connection if (feedsClient != null) { feedsClient.shutdown(); } } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("application/json;charset=UTF-8"); PrintWriter out = response.getWriter(); String action = request.getParameter("action"); String feedname = null; if (action == null) { try { response.sendRedirect("replayFeed.html"); } catch (IOException e1) { System.out.println("doGet IOException: Can not redirect"); response.setStatus(HttpServletResponse.SC_BAD_REQUEST); out.println("{\"error\":\"action parameter not specified\"}"); } return; } // Read the feed name for the actions that need it if (action.equals("start") || action.equals("stop") || action.equals("delete")) { feedname = request.getParameter("feedname"); if (feedname == null) { out.println("{\"error\":\"Start and stop actions require the parameter 'feedname'\"}"); return; } } // Other parameters that are action-specific will be read from within the functions int res; if (action.equals("list")) res = listRunningFeeds(out); else if (action.equals("start")) res = startReplay(feedname, out, request); else if (action.equals("stop")) res = stopReplay(feedname, out); else if (action.equals("delete")) res = deleteReplay(feedname, out); else if (action.equals("delete_all")) res = deleteAllFeeds(out, request); else { response.setStatus(HttpServletResponse.SC_BAD_REQUEST); out.println( "{\"error\":\"Unknown action, should be one of: 'list', 'start', 'stop', 'delete', 'delete_all'\"}"); return; } // error messages will be printed by the function if (res < 0) { response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR); } else if (res > 0) { response.setStatus(HttpServletResponse.SC_BAD_REQUEST); } } // All below functions return 0 if ok -1 if server error 1 if bad request int listRunningFeeds(PrintWriter out) { if (replayList == null || feedsClient == null) { out.println("{\"error\":\"Server not correctly initialised\"}"); return -1; } int len; StringBuilder replayNames = new StringBuilder(); for (String name : replayList.keySet()) { replayNames.append("\"" + name + "\","); } // Delete last comma character in name list if ((len = replayNames.length()) > 0) replayNames.deleteCharAt(len - 1); out.println("{\"list\":[" + replayNames.toString() + "]}"); return 0; } int deleteAllFeeds(PrintWriter out, HttpServletRequest request) { if (replayList == null || feedsClient == null) { out.println("{\"error\":\"Server not correctly initialised\"}"); return -1; } if (!"delete all replays".equals(request.getParameter("confirm"))) { out.println( "{\"error\":\"To prevent accidental deletion, an additional parameter 'confirm=delete+all+replays' is required\"}"); return 1; } cancelTimers(); // Wait a bit for the timers to stop try { Thread.sleep(1000); } catch (InterruptedException e) { } // Delete the replay databases and remove them from feeds list long startTime = System.currentTimeMillis(); int doccount = 0; for (String DBname : feedsClient.context().getAllDbs()) { if (DBname.startsWith("replay_")) { doccount++; feedsClient.context().deleteDB(DBname, "delete database"); // also remove from feeds list if existing String rev; if ((rev = feedsClient.getRevision(DBname)) != null) { feedsClient.remove(DBname, rev); } } } out.println("{\"status\": \"deleted " + doccount + " replays in " + (System.currentTimeMillis() - startTime) + " ms\"}"); return 0; } int deleteReplay(final String name, PrintWriter out) { if (replayList == null || feedsClient == null) { out.println("{\"error\":\"Server not correctly initialised\"}"); return -1; } // First stop the replay, ignore if the replay is not running stopReplay(name, null); StringBuffer error = new StringBuffer(); // Delete the database if (feedsClient.context().getAllDbs().contains(name)) { feedsClient.context().deleteDB(name, "delete database"); } else { error.append("feed database was not found"); } // And remove from feeds list if existing String rev; if ((rev = feedsClient.getRevision(name)) != null) { feedsClient.remove(name, rev); } else { if (error.length() > 0) { error.append(", "); } error.append("feed was not present in feeds list"); } if (error.length() > 0) { out.println("{\"error\":\"Deleted replay, but following error(s) occured: " + error.toString() + "\"}"); return 1; } else { out.println("{\"status\":\"Deleted replay\"}"); return 0; } } /* * Returns 0 on success, 1 on bad input, -1 on error and prints description in out */ int startReplay(final String name, PrintWriter out, HttpServletRequest request) { if (replayList == null || feedsClient == null) { out.println("{\"error\":\"Server not correctly initialised\"}"); return -1; } if (replayList.size() > 30) { out.println("{\"error\":\"Too many replays currently running (" + replayList.size() + "), please stop some before retrying\"}"); return 1; } String newname; // If the user provides a new name, prefix it with "replay_", else prefix the original name if (request.getParameter("newname") != null) { newname = "replay_" + Common.cleanString(request.getParameter("newname").toString()); } else newname = "replay_" + name; // Do not start a new replay if already running if (replayList.containsKey(newname)) { out.println("{\"status\":\"Replay into '" + newname + "' already running\"}"); return 0; } // Add a new entry on replayList to avoid starting more replays on consecutive requests ReplayTaskData data = new ReplayTaskData(); replayList.put(newname, data); // Check if name and newname already exist the database List<String> DBs = feedsClient.context().getAllDbs(); // If source feed name does not exist, or the feeds db has no description return error if (!DBs.contains(name) || !feedsClient.contains(name)) { replayList.remove(newname); out.println("{\"error\":\"Source feed does not exist or has no description in 'feeds' list\"}"); return 1; } // Open a connection to the source and destination DBs try { data.srcClient = new CouchDbClient(name, false, "http", server, port, user, pass); // Create the new database if it does not exist data.dstClient = new CouchDbClient(newname, true, "http", server, port, user, pass); } catch (Exception e) { replayList.remove(newname); cancelReplay(data); if (data.srcClient == null) { // No connection could be made to source client out.println("{\"error\":\"Could not access DB '" + name + "' \"}"); } else { // Connection to srcClient was successful, but couldn't connect to target out.println("{\"error\":\"Could not access DB '" + newname + "' \"}"); } return -1; } // If the new db does not have design document for view, add it if (!data.dstClient.contains("_design/get_data")) { String viewDoc = "{\n" + "\t\"_id\": \"_design/get_data\",\n" + "\t\"language\": \"javascript\",\n" + "\t\"views\": {\n" + "\t\t \"by_date\": {\n" + "\t\t\t \"map\": \"function(doc) {\\nif(doc.timestamp && doc.data) {\\nemit(doc.timestamp, doc.data);\\n}\\n}\"\n" + "\t\t }\n" + "\t}\n" + "}\n"; try { data.dstClient.saveJsonText(viewDoc); } catch (Exception e) { replayList.remove(newname); // release previously initialised clients cancelReplay(data); out.println("{\"error\":\"Could not add design document in DB '" + newname + "' \"}"); return -1; } } // In feeds database copy the feed description from original feed to new feed // Get the revision of new feed description document, null means it does not exist String rev = feedsClient.getRevision(newname); try { // Get the original feed description JsonObject feedObj = feedsClient.find(JsonObject.class, name); // Change the document id to match new feed feedObj.addProperty("_id", newname); // If the document was not present in feeds before, remove _rev property and save if (rev == null) { feedObj.remove("_rev"); feedsClient.save(feedObj); } // otherwise set _rev property to the revision and update the document else { feedObj.addProperty("_rev", rev); feedsClient.update(feedObj); } } catch (Exception e) { replayList.remove(newname); // release previously initialised clients cancelReplay(data); out.println( "{\"error\":\"Could not copy feed description from '" + name + "' to '" + newname + "' \"}"); return -1; } Long startMillis = null, endMillis = null; String startDate = request.getParameter("start_date"); if (startDate != null) { try { startMillis = Long.parseLong(startDate); } catch (NumberFormatException e) { try { startMillis = javax.xml.bind.DatatypeConverter.parseDateTime(startDate).getTimeInMillis(); } catch (IllegalArgumentException e1) { out.println("{\"error\":\"Invalid start date '" + startDate + "'\"}"); return 1; } } } String endDate = request.getParameter("end_date"); if (endDate != null) { try { endMillis = Long.parseLong(endDate); } catch (NumberFormatException e) { try { endMillis = javax.xml.bind.DatatypeConverter.parseDateTime(endDate).getTimeInMillis(); } catch (IllegalArgumentException e1) { out.println("{\"error\":\"Invalid end date '" + endDate + "'\"}"); return 1; } } } if (startMillis != null && endMillis != null && startMillis > endMillis) { out.println("{\"error\":\"End time is before start time\"}"); return 1; } String repeatStr = request.getParameter("repeats"); if (repeatStr != null) { try { data.repeats = Integer.parseInt(repeatStr); } catch (NumberFormatException e) { out.println("{\"error\":\"Invalid number of repeats '" + repeatStr + "'\"}"); return 1; } } else { // only repeat once data.repeats = 1; } List<JsonObject> resList; // Get the first 2 documents, write the first one in the new feed DB and keep the other to // send in the next iteration if (startMillis != null && endMillis != null) { resList = data.srcClient.view("get_data/by_date").startKey(startMillis).endKey(endMillis).limit(2) .query(JsonObject.class); } else if (startMillis != null) { resList = data.srcClient.view("get_data/by_date").startKey(startMillis).limit(2) .query(JsonObject.class); } else if (endMillis != null) { resList = data.srcClient.view("get_data/by_date").endKey(endMillis).limit(2).query(JsonObject.class); } else { resList = data.srcClient.view("get_data/by_date").limit(2).query(JsonObject.class); } if (resList == null || resList.size() != 2) { replayList.remove(newname); // release previously initialised clients cancelReplay(data); out.println("{\"error\":\"Feed '" + name + "' contains no data or only one measurement\"}"); return 1; } data.count = 0; data.feedStart = resList.get(0).get("key").getAsLong(); data.nextDocTime = resList.get(1).get("key").getAsLong(); data.replayStart = System.currentTimeMillis(); data.feedEnd = (endMillis == null ? Long.MAX_VALUE : endMillis); // Calculate the time difference from start to next document long diff = data.nextDocTime - data.feedStart; // Update time in the first document and save into DB data.dstClient.save(changeDocumentTime(resList.get(0), data.replayStart)); // Update time in the second document and store for next run data.nextDoc = changeDocumentTime(resList.get(1), data.replayStart + diff); // Set the timer to save the next doc data.tm = new Timer("timer_" + newname); data.tm.schedule(new replayTimer(newname), diff); out.println("{\"status\":\"Started replay of '" + name + "' into '" + newname + "'\"}"); return 0; } class replayTimer extends TimerTask { String name; replayTimer(String name) { this.name = name; } @Override public void run() { ReplayTaskData data = replayList.get(name); List<JsonObject> resList = null; if (data == null) return; // Next document was already loaded before, save it try { data.dstClient.save(data.nextDoc); } catch (org.lightcouch.CouchDbException e) { System.err.println("CouchDB Exception saving"); } if (data.nextDocTime + 1 < data.feedEnd) { try { // Get a new document // resList = data.srcClient.view("get_data/by_date").startKey(data.nextDocTime + 1).limit(1) // .query(JsonObject.class); resList = data.srcClient.view("get_data/by_date").startKey(data.nextDocTime + 1) .endKey(data.feedEnd).limit(1).query(JsonObject.class); } catch (Exception e) { System.err.println("CouchDB Exception reading"); } } // No more data available if (resList == null || resList.size() != 1) { boolean restart = false; if (++data.count == data.repeats) { // We have done the required number of repetitions cancelReplay(data); replayList.remove(name); } else { try { resList = data.srcClient.view("get_data/by_date").startKey(data.feedStart) .endKey(data.feedEnd).limit(1).query(JsonObject.class); } catch (Exception e) { System.err.println("CouchDB Exception reading"); } if (resList != null && resList.size() == 1) { // Restart a new loop restart = true; data.replayStart = System.currentTimeMillis(); } } // System.out.println("Source feed for '" + name + "' contains no more data"); if (!restart) return; } data.nextDoc = resList.get(0); data.nextDocTime = data.nextDoc.get("key").getAsLong(); // Calculate the difference between start of feed and doc time long diff1 = data.nextDocTime - data.feedStart; // Check how much time has passed since start of replay long diff2 = System.currentTimeMillis() - data.replayStart; // Calculate how much time remains till next run long newTime = diff1 - diff2; if (newTime < 0) newTime = 0; // Update the new document time based on diff1 data.nextDoc = changeDocumentTime(data.nextDoc, data.replayStart + diff1); try { // reschedule next timer according to actual time passed data.tm.schedule(new replayTimer(name), newTime); } catch (IllegalStateException e) { // We can get here if the timer was stopped in the meantime, suppress warning } // System.out.println("Running " + name + ", count = " + data.count++ + ", nextTime = " + data.nextDocTime); } } int stopReplay(String name, PrintWriter out) { if (replayList == null) return -1; if (!replayList.containsKey(name)) { if (out != null) out.println("{\"error\":\"Replay of '" + name + "' not running\"}"); return 1; } ReplayTaskData data = replayList.get(name); cancelReplay(data); replayList.remove(name); if (out != null) out.println("{\"status\":\"Stopped replay of '" + name + "'\"}"); return 0; } private void cancelReplay(ReplayTaskData data) { // Stop timer if (data.tm != null) data.tm.cancel(); // Close CouchDB clients if (data.srcClient != null) data.srcClient.shutdown(); if (data.dstClient != null) data.dstClient.shutdown(); } // Stop all running timers private void cancelTimers() { for (String name : replayList.keySet()) { cancelReplay(replayList.get(name)); } replayList.clear(); } JsonObject changeDocumentTime(JsonObject Document, long newTimeMillis) { String xmlDateTime; boolean fixMillis = false; /* * If the millis is divisible by 1000, printDateTime does not add a decimal printout. This workaround fixes this * by adding a millisecond before printing */ if (newTimeMillis % 1000 == 0) { fixMillis = true; newTimeMillis++; } synchronized (this) { cal.setTimeInMillis(newTimeMillis); xmlDateTime = javax.xml.bind.DatatypeConverter.printDateTime(cal); } // Undo the change done previously and also fix the printout if (fixMillis) { xmlDateTime = xmlDateTime.replace(".001Z", ".000Z"); newTimeMillis--; } JsonObject newDoc = new JsonObject(); newDoc.addProperty("_id", xmlDateTime); newDoc.addProperty("timestamp", newTimeMillis); JsonObject data = Document.get("value").getAsJsonObject(); // If "time" already exists, update it if (data.get("time") != null) { data.addProperty("time", xmlDateTime); newDoc.add("data", data); } else { // If not already existing, add "time" property at the beginning JsonObject data1 = new JsonObject(); data1.addProperty("time", xmlDateTime); for (Entry<String, JsonElement> e : data.entrySet()) { data1.add(e.getKey(), e.getValue()); } newDoc.add("data", data1); } return newDoc; } String getDocument(String name) { InputStream is = feedsClient.find(name); InputStreamReader isr = null; try { isr = new InputStreamReader(is, "UTF-8"); } catch (UnsupportedEncodingException ignore) { } // Store the document to a StringBuilder in order to convert to string StringBuilder docStrBuilder = new StringBuilder(); try { char[] buf = new char[4 * 1024]; // 4 KB char buffer int len; while ((len = isr.read(buf, 0, buf.length)) != -1) { docStrBuilder.append(buf, 0, len); // System.out.println("Total read thus far:"+reqStrBuilder.toString()); } } catch (IOException e1) { System.err.println("Can not read input, received data:" + docStrBuilder.toString()); try { is.close(); } catch (IOException e) { } return null; } // Close the input stream as requested by find() try { is.close(); } catch (IOException e) { } return docStrBuilder.toString(); } class ReplayTaskData { Timer tm; CouchDbClient srcClient, dstClient; JsonObject nextDoc; int count, repeats; long nextDocTime, replayStart, feedStart, feedEnd; } }