Your browser, my storage


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HTML5 introduces the new trend of offline storage for applications and data.

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Your browser, my storage

  1. 1. Your browser, my storage a new approach on data storing Francesco Fullone ff AT
  2. 2. Who am I Francesco Fullone aka Fullo - PHP developer since 1999 - President - and Open Source Evangelist - CEO @ - Nerd and geek
  3. 3. What we want is a lot of storage space, on the client, that persists beyond a page refresh and isn’t transmitted to the server. ~ M. Pilgrim
  4. 4. Persistent local storage is one of the areas where client applications traditionally win against web applications.
  5. 5. A jump in the past
  6. 6. Cookies are introduced in HTTP/1.0, limited to only 20 per domain and 4KB each.
  7. 7. Cookies are sent to and from client at any connection.
  8. 8. Microsoft with Internet Explorer 6 introduced dHTML and the userData API to store up to 64KB of data
  9. 9. Mozilla introduced with Firefox 2 the DOM Storage API, it will then know as Web Storage.
  10. 10. Adobe, in 2002, created the Flash Cookies aka “Local Shared Objects” for Flash 6. Data storage increased to 100KB but it was difficult to be used.
  11. 11. With Flash 8, in 2006, Adobe introduced the ExternalInterface to allow Js to access to the stored resources.
  12. 12. Between 2005 and 2007 is written by Brad Neuberg as a Js->Flash bridge to manage bigger chunks of data (with user prompt over 1MB).
  13. 13. Google created Gears in 2007, that introduced a database paradigm (based on SQLite) to the storage problem.
  14. 14. All these storage systems had different APIs, a common platform is needed by all the browser vendors.
  15. 15. The two approaches of storing: Application Cache Offline storage
  16. 16. Application Caching involves saving the application's core logic and user-interface. work/#applicationcache
  17. 17. It is enabled by a file .manifest that declares which resources have to be saved locally. (limited to 5MB).
  18. 18. CACHE MANIFEST # Explicitly cached entries CACHE: index.html stylesheet.css images/logo.png scripts/main.js # Resources that require the user to be online. NETWORK: login.php /myapi # static.html will be served if main.php is inaccessible # offline.jpg will be served in place of all images in images/large/ FALLBACK: /main.php /static.html images/large/ images/offline.jpg
  19. 19. Data storage is about capturing specific data, or resources the user has expressed interest in.
  20. 20. Approaches to Data Storage
  21. 21. Web Storage is the simpler implementation of the Data Storage paradigm.
  22. 22. Web Storage is based on a structure of key-value pairs like any JavaScript object. localStorage.setItem("bar", foo);
  23. 23. Web Storage can save up to 5MB but only as strings. So we have to force a casting if needed. var bar = parseInt(localStorage["bar"]);
  24. 24. Web Storage should be local based or session based. var bar = localStorage["bar"]; var foo = sessionStorage["foo"];
  25. 25. sessionStorage mantains a storage area that's available for the duration of the web session. Opening a new window/tab will create a new session.
  26. 26. localStorage relies only on client, so we have to track changes and use to sync server and client if needed.
  27. 27. Web SQL Database is just an offline SQL implementation, based on SQLite.
  28. 28. this.db = openDatabase('geomood', '1.0', 'Geo', 8192); this.db.transaction(function(tx) {   tx.executeSql("create table if not exists checkins(id    integer primary key asc, time integer,    latitude float, longitude float, mood   string)",   [],                 function() { console.log("siucc"); } »   ); });
  29. 29. Web SQL Database is not (yet) supported by Microsoft and Mozilla, instead it is on browsers based on webkit.
  30. 30. IndexedDB is a nice compromise between Web Storage and Web SQL Database.
  31. 31. IndexedDB allows to create an index on a certain field stored in a standard key->value mapping.
  32. 32. IndexedDB is promoted by all browsers vendor, but is not yet officially supported by anyone! Firefox 4 beta has a partial implementation.
  33. 33. FileAPI or File Storage will give us a way to store a lot of data.
  34. 34. File API includes FileReader and FileWriter APIs. Actually (FileReader) is partially supported only by Chrome.
  35. 35. First steps on offline storage development.
  36. 36. HTML 5 Confusion
  37. 37. Detect if the storing feature is supported by the browser (with modernizr), otherwise degradate to something else. (ie.
  38. 38. Protect against lost data, sync automatically.
  39. 39. Automatically detect when users are online.
  40. 40. Do not exceed in storing data, you can store binary data base64 encoded but remember the pitfalls in performance.
  41. 41. Avoid race conditions. If possible use WebSQL to use its transactions features.
  42. 42. ?
  43. 43. phpDay 2011 12-14 Maggio 2011
  44. 44. via Quinto Bucci 205 47023 Cesena (FC) info AT rate this talk: