Can you write REAL applications with AJAX? Phil Sarin Advanced UI Software April 15, 2009

Problem: Many web apps stink

Rich Internet Applications (RIAs) Easy deployment and maintenance “Desktop-like” interactivity Willing to sacrifice some “webness” (e.g., bookmarks)

RIA Approaches Browser plug-in ▫Flash/Flex, Java Swing, Silverlight ▫Potentially greater interactivity, higher barrier to adoption ▫Concerns about openness/control In browser, no plug-ins ▫AJAX ▫Lower barrier to adoption ▫Cross-browser mayhem?

Questions for today Can we approach AJAX development like “regular” GUI development? What are the approaches/tradeoffs? What’s likely to become popular?

What is AJAX?

AJAX event handling

Some History

History: Hill Climbing

RIA: Which hill to climb?

Approaching RIAs from two hills HTTPDirect Manipulation Origins in early web sitesOrigins in desktop GUIs Built around the HTTP protocolBuilt around user events Generating HTMLLaying out graphical objects

The HTTP Hill

Static Pages Server fetches and returns a web page Initially just text-based With Mosaic, pictures too

The HTTP Hill Dynamic Pages Server-side ▫CGI (mostly perl) Client-side ▫Javascript

The HTTP Hill “Frameworks” MVC support (Struts 1 & 2, Rails, Django) Easier HTML generation (JSP, ERB, Freemarker, …) State/sessions Javascript libraries (Prototype, DOJO, jQuery)

The HTTP Hill Pros/Cons (prior to AJAX) +Very cheap for simple sites +Reasonably flexible ▫Mail clients! +Web-friendly ▫Bookmarkable ▫Indexable -Slow feedback -Minimal interactivity -Cross-browser mayhem

The Direct Manipulation Hill

GUI Toolkits Common widget set across applications Standalone or client-server

The Direct Manipulation Hill for Internet applications Browser Plug-Ins Flash, Java, Silverlight Took a long time to catch on

The Direct Manipulation Hill Pros/Cons +Timely feedback +Programming power (behaviors, constraints – at least possible) +Common widgets (consistency, usability) +Flash/etc: more consistent runtime platform -Flash/etc: needs a plug-in -Cross-platform issues still exist -Proprietary runtime platform

Where does AJAX fit in?

Both hills!

AJAX on the HTTP Hill Tactical features ▫Autocomplete ▫Drag and drop AJAX-aware code ▫Raw Javascript/HTML/CSS ▫Or with a library Okay for some applications Too limiting for RIAs Not the focus of this talk

Direct Manipulation AJAX

AJAX on the Direct Manipulation Hill Separate development environment from runtime environment. Runtime environment: HTML/Javascript/CSS (AJAX) Development environment: toolkit in another language Two approaches: thin and fat

Thin Client AJAX Approach

Example: Google Maps (pretend it’s a thin client app)

A Grid of Images

Example: Google Maps

Sequence

Thin Client Pros and Cons +Simple programming: ignore the network +All your code runs server-side +Programmers love it! +Undo, behaviors, constraints: all possible! -Scalability (server-side state, lots of requests) -Slow feedback: network hop for each user action

Fat Client AJAX Approach

Example: Google Maps

Sequence

Wait a second… No AJAX calls involved in moving the map around! ▫Mostly Javascript. ▫New image requests are synchronous Example AJAX call: adding an intermediate destination

Fat Client Pros and Cons +Scalable (client-side state, fewer HTTP calls) +Fast feedback +Undo, behaviors, constraints possible… -…but undo more complex than on the desktop -More complicated: network-aware, distributed

Example AJAX Toolkits Google Web Toolkit: Fat Client ▫Write in Java, compiled to Javascript Cappuccino: Fat Client Echo2: Thin Client ▫Write in Java ▫No HTML/CSS (proprietary stylesheet language) Echo3 (Java – Beta): hybrid ▫Thin widgets in Java ▫Fat widgets in Javascript

So, is AJAX viable for RIAs? Fat AJAXThin AJAXPlugin (Flash, Swing) Feedback SpeedWinner (tied) Interactive Potential Winner ScalabilityWinner (tied) Cross-platform Consistency Winner MomentumGoogle does a lot of work for you. ?Adobe does a lot of work for you. Ease of Programming Winner

Thin vs Fat AJAX? Thin AJAX: Squeezed out ▫Insufficient if interactivity matters ▫Not as easy as an HTTP-oriented application Fat AJAX: How does it compare to plug ins? ▫Developer adoption? ▫Application philosophy?

Some Toolkits

GWT: A Toolkit… Laying out widgets in a container “panel” Events and handlers // Create a Horizontal Panel HorizontalPanel hPanel = new HorizontalPanel(); // Leave some room between the widgets hPanel.setSpacing(5); // Add some content to the panel for (int i = 1; i < 5; i++) { hPanel.add(new Button("Button " + i)); } ideUserInterface.html

…with non-strict abstractions Styling with CSS Directly embed Javascript Raw HTML Direct DOM manipulation private native void putElementLinkIDsInList(Element elt, ArrayList list) /*-{ var links = elt.getElementsByTagName("a"); for (var i = 0; i < links.length; i++ ) { var link = links.item(i); link.id = ("uid-a-" + i); t;) (link.id); } }-*/; ideUserInterface.html

Cappuccino: A different philosophy “When you program in Cappuccino, you don't need to concern yourself with the complexities of traditional web technologies like HTML, CSS, or even the DOM. The unpleasantries of building complex cross browser applications are abstracted away for you.”

Javascript as “assembly language”

Cappuccino vs GWT Philosophical question GWT: RIAs that are part of of the web Cappuccino: RIAs deployed over the web ▫Alternative to Flash/Flex

Finally

Recommendations If you’re serious about RIAs, climb the direct manipulation hill. Don’t limit yourself to Thin AJAX. AJAX sweet spot: Applications that are part of the web. AJAX is an implementation alternative for applications deployed over the web.

References 1 adaptive path » ajax: a new approach to web applications. (n.d.).. Retrieved April 8, 2009, from Adobe wants to be the Microsoft of the Web at Ted Leung on the Air. (n.d.).. Retrieved April 8, 2009, from wants-to-be-the-microsoft-of-the-web/. wants-to-be-the-microsoft-of-the-web/ Cappuccino Web Framework - Build Desktop Class Applications in Objective-J and JavaScript. (n.d.).. Retrieved April 15, 2009, from Comparing the Google Web Toolkit to Echo2. (n.d.).. Retrieved April 9, 2009, from

References 2 Dare Obasanjo aka Carnage4Life - What Comes After AJAX? (n.d.).. Retrieved April 8, 2009, from 4ed2-b387-c9ec966d ed2-b387-c9ec966d8418 Developer's Guide - Google Web Toolkit - Google Code. (n.d.).. Retrieved April 9, 2009, from Echo2 Technical Overview | Echo Web Framework. (n.d.).. Retrieved April 8, 2009, from Echo2 Tutorial | Echo Web Framework. (n.d.).. Retrieved April 8, 2009, from

References 3 Echo2 versus GWT The Register. (n.d.).. Retrieved April 9, 2009, from Feigin, B. (n.d.). Cappuccino and Objective-J. Retrieved from %20Cappuccino.pptx. %20Cappuccino.pptx Following up on “The Microsoft of the Web” at Ted Leung on the Air. (n.d.).. Retrieved April 8, 2009, from up-on-the-microsoft-of-the-web/. up-on-the-microsoft-of-the-web/ LaszloWhitePaper.pdf. (n.d.).. Retrieved April 8, 2009, from

References 4 Mesbah, A., & van Deursen, A. (2006). An Architectural Style for Ajax. cs/ Retrieved April 8, 2009, from C Shan, & Winnie W Hua. (2006). Taxonomy of Java Web Application Frameworks. In e-Business Engineering, ICEBE '06. IEEE International Conference on (pp ). doi: /ICEBE