The document discusses how to use Google Web Toolkit (GWT) and Google Gears to create web applications that can run offline. It explains that GWT allows developers to write applications in Java that compile to optimized JavaScript. Google Gears provides features like local data storage, databases and caching that allow applications to work without an internet connection. The document provides details on using the Gears manifest file to cache resources, interacting with the SQLite database to store local data, and syncing data when the application regains connectivity.

1. Going Offline With GWT and Gears Tom Peck AppEngines, LLC

2. Why? Web apps are great ... if you can connect Planes Trains Automobiles Users may not want their data in the cloud Increase response time for online apps

3. How? GWT - Google Web Toolkit Google Gears

4. Google Web Toolkit

5. Write AJAX Applications in Java

7. Google Web Toolkit Program in Java, compile to JavaScript JavaScript is highly optimized Programming model similar to Swing RPC mechanism for calling server Debug web apps in Eclipse http://code.google.com/webtoolkit http://code.google.com/p/gwt-google-apis/

8. Google Gears

12. Google Gears Browser Plugin (FireFox, Internet Explorer) http://gears.google.com Features: LocalServer (“programmable cache”) SQLite Database Worker Threads for JavaScript

13. Take Your App Offline Manifest file of your app’s resources Download resources Create database schema Go

14. Manifest File { "betaManifestVersion": 1, "version": "Version 1.0", "entries": [ { "url": "7EEF8FB6BA93DAAD0AB9A64C6D6471FE.cache.html" }, { "url": "7EEF8FB6BA93DAAD0AB9A64C6D6471FE.cache.js" }, { "url": "7EEF8FB6BA93DAAD0AB9A64C6D6471FE.cache.xml" }, { "url": "87AA9AB2FB06214DC10C32E7B35C5F6A.cache.html" }, { "url": "87AA9AB2FB06214DC10C32E7B35C5F6A.cache.js" }, { "url": "87AA9AB2FB06214DC10C32E7B35C5F6A.cache.xml" }, { "url": "884D363F8887607F5180653AA6B10E6D.cache.html" }, { "url": "884D363F8887607F5180653AA6B10E6D.cache.js" }, { "url": "884D363F8887607F5180653AA6B10E6D.cache.xml" }, { "url": "com.company.CompanyApp.nocache.js" }, { "url": "gears_init.js" }, { "url": "gwt.js" }, { "url": "CompanyApp.html" }, { "url": "default.css" }, { "url": "logo1.png" }, ] }

15. Load Resources LocalServer localServer = new LocalServer();ManagedResourceStore managedRS = localServer.createManagedResourceStore("CompanyApp"); managedRS.setManifestURL(" http://company.com/manifest.json "); managedR.checkForUpdate(); new Timer() { public void run() { switch (managedResourceStore.getUpdateStatus()) { case ManagedResourceStore.UPDATE_OK: statusLabel.setText("Ready for offline access"); break ; case ManagedResourceStore.UPDATE_CHECKING: case ManagedResourceStore.UPDATE_DOWNLOADING: schedule(500); break ; case ManagedResourceStore.UPDATE_FAILED: statusLabel.setText("Unable to go offline); break ; } } }.schedule(500);

16. Gears Database Uses SQLite Simplified SQL syntax http://sqlite.org

17. Create Database “create table if not exists person (id integer, first_name text, last_name text)” Datatypes: Integer, Real, Text, Blob Constraints: “primary key”, “not null”, “unique”, etc.

18. Create Database private Database m_database = null; try { m_database = new Database(“Test”); ResultSet rs = m_database.execute(“create table...”); rs.close(); } // try catch (Exception e) { // Gears not installed } // catch

19. Queries String sql = “select id, first_name, last_name from person”; ResultSet rs = m_database.execute(sql); ArrayList results = new ArrayList(); while (rs.isValidRow()) { PersonBean person = new PersonBean(); person.setID(rs.getFieldAsInt(0)); person.setFirstName(rs.getFieldAsString(1)); person.setLastName(rs.getFieldAsString(2)); results.add(person); rs.next(); } // while rs.close();

20. Insert, Update String args[] = new String[3]; args[0] = Integer.toString(person.getID()); args[1] = person.getFirstName(); args[2] = person.getLastName();ResultSet rs = m_database.execute(“insert into person (id, first_name, last_name) values (?,?,?)”, args); rs.close(); args = new String[3]; args[0] = person.getFirstName(); args[1] = person.getLastName();args[2] = Integer.toString(person.getID()); rs = m_database.execute(“update person set first_name=?, last_name=? where id=?)”, args); rs.close();

21. Demo

22. Demo Source Code http://www.appengines.com/Stickies.zip

23. Syncing Issues Need GUIDs Need timestamps (SQLite has no Date) Need a strategy: Last one wins Lock / Check out Let user decide

24. Conclusion Google Gears allows web applications to run offline Google Web Toolkit makes it easy to program Gears

25. Thank You