Raible Designs

Choosing an Ajax Framework

This past week, my colleagues and I have been researching Ajax Frameworks. We're working on a project that's following SOFEA-style architecture principles and we want the best framework for our needs. I'm writing this post to see 1) if you, the community, agree with our selection process and 2) to learn about your experiences with the frameworks we're evaluating. Below is the process we're following to make our choice.

1. Choose a short list of frameworks to prototype with.
2. Create an application prototype with each framework.
3. Document findings and create a matrix with important criteria.
4. Create presentation to summarize document.
5. Deliver document, presentation (with demos) and recommendation.

For #1, we chose Ext JS, Dojo, YUI and GWT because we feel these Ajax libraries offer the most UI widgets. We also considered Prototype/Scriptaculous, jQuery and MooTools, but decided against them because of their lack of UI widgets.

For #2, we time-boxed ourselves to 3 days of development. In addition to basic functionality, we added several features (i.e. edit in place, drag and drop, calendar widgets, transitions, charts, grid) that might be used in the production application. We all were able to complete most of the functionality of the application. Of course, there's still some code cleanup as well as styling to make each app look good for the demo. The nice thing about doing this is we're able to look at each others code and see how the same thing is done in each framework. None of us are experts in any of the frameworks, so it's possible we could do things better. However, I think it's good we all started somewhat green because it shows what's possible for someone relatively new to the frameworks.

For #3, we're creating a document with the following outline:

Introduction

Ajax Framework Candidates
(intro and explanation)

  Project Information
  (history)
  (license / cost)
  (number of committers)
  (support options)
  (mailing list traffic (nov/dec 2008))

Matrix and Notes

Conclusion

For the Matrix referenced in the outline above, we're using a table with weights and ranks:

Our strategy for filling in this matrix:

• Customer adjusts the weight for each criteria (removing/adding as needed) so all weights add up to 1.
• We rank each framework with 0, .5 or 1 where 0 = doesn't satisfy criteria, .5 = partially satisfies, 1 = satisfies.

The list of criteria provided to us by our client is as follows (in no particular order).

• Quality of Documentation/Tutorials/Self Help
• Browser support (most important browsers/versions based on web stats)
• Testability (esp. Selenium compatibility)
• Licensing
• Project health/adoption
• Performance
• Scalability
• Flexibility/extensibility
• Productivity (app dev, web dev)
• Richness of widget/component library
• Charting capability
• Ability to create new widgets
• Match to existing Java team skill-set
• Ease of deployment (on Ops, QA, Users)
• Degree of risk generally
• Ability to integrate with existing site (which includes Prototype)
• Easy to style with CSS
• Validation (esp. marking form elements invalid)
• Component Theme-ing/Decoration
• CDN Availability (i.e. Google's Ajax Libraries API or Ext CDN)

What do you think? How could this process be improved? Of course, if you have framework answers (0, .5 or 1) for our matrix, we'd love to hear your opinions.

AppFuse Light » AppFuse, Maven Archetypes and Shared Web Assets

Last night, I stayed up into the wee hours of the morning working on something I've been wanting to do for a long time. It wasn't until I was trouncing around the woods in Montana that I realized how easy it would be. The something I've wanted to do was to modify AppFuse Light to use AppFuse's core modules (service and dao). It only took me a few hours to make it happen and it inspired additional ideas.

I believe the major mistake we made in AppFuse 2.x was making it easy for user's to upgrade their applications. We currently use the maven-war-plugin and our own maven-warpath-plugin to make it possible to include AppFuse classes and assets in your project. You can easily start a new project w/o having a whole bunch of files in your project. The problem is, you can't easily use "mvn jetty:run" to work on your project. Of course, you can use "mvn appfuse:full-source" to solve this, but I'm starting to think more and more that "full-source" should be the default. This is what we did in 1.x and it seems to be the more natural pattern for folks using AppFuse.

That hard part about moving to "full-source" by default is coming up with a way to share common assets and classes among wars and war projects. Sure, I can copy all the shared images, css and js into each project - but that could become a maintenance nightmare. Subversion 1.5 with relative svn:externals might solve this, but it still seems kinda hacky. I don't want to use the maven-war-plugin because the overlay is kinda hokey and I think it's easier for users to understand when everything is in their project. AppFuse's current directory structure in SVN looks as follows. I've added indicators of what is in each directory.

Rather than using AppFuse's current (manual) archetype-creation process, I'd like to move to a more automated creation process using the maven-archetype-plugin's create-from-project feature. I'd like to figure out a way where I can have the source code and assets from web/common included in each of the other web/* projects (both when using "jetty:run" and "archetype:create-from-project"). One idea I thought of is to make Jetty/Maven aware of multiple src/war directories for "jetty:run" and "package" and then somehow hook into the archetype plugin at creation time to pull in the shared resources. I don't know if something like this is possible. If you know of a good solution to this shared web assets issue, I'd love to hear about it.

Back to AppFuse Light. If I can figure out how to solve shared resources in web modules, I can use this in AppFuse Light to move to a modular SVN structure vs. its current "use Ant to create different combinations" setup. If a modular structure (like appfuse/web/*) is possible for AppFuse Light, I believe it makes sense to move its source into AppFuse's SVN repository. Below is how the directory structure might look after this move.

With this addition and "archetype:create-from-project", we should be able to create all the basic and light archetypes automatically. We'll probably still need a manual archetype-creation process for modular archetypes, but I'm OK with that.

The last thing I'm struggling with is figuring out the best way to create archetypes for something like AppFuse. In the past, we've used dependencies to allow users to inherit dependencies and their versions. This works, but it results in a lot of duplicate XML (in projects and archetypes) for developers. Last night, I tried using a parent project instead of dependencies and it seems to work much better. Not only do you inherit dependencies, but you also inherit plugins, profiles and properties. If you inherit, you can override, which is slick.

If you're an AppFuse user, how would you feel about having an AppFuse module as your project's parent? Would you prefer that, dependencies on AppFuse or full-source with no dependencies on AppFuse? Regardless of parent vs. dependencies, I think running "appfuse:full-source" should allow you to de-couple your project from AppFuse.

Colorado Software Summit 2008 Wrapup

Last week, I attended the Colorado Software Summit in Keystone and had a great time. Not only was the weather beautiful and the food delicious, the sessions I attended were awesome. If you ever get a chance to go to this conference, I highly recommend it. It's like being on vacation and learning with a bunch of old friends.

Yan Pujante also attended this conference and documents his experience, photography and presentations in Colorado Software Summit 2008.

Below is a list of my entries for all the sessions I attended.

• Building LinkedIn's Next Generation Architecture with OSGi by Yan Pujante
• Comprehensive Project Intelligence with Jason van Zyl
• What's Coming in Spring 3.0
• Applying Flash to Java: Flex and OpenLaszlo with Dustin Marx
• Building Rich Applications with Appcelerator
• Taking Apache Camel for a Ride with Bruce Snyder
• Core Animation with Bill Dudney
• RESTful Web Applications with Subbu Allamaraju

For next year, I think the conference should shorten its sessions (from 90 to 60 minutes), invite more speakers and cut the price in half (to $999 per person). How do you think the Software Summit could be improved?

RESTful Web Applications with Subbu Allamaraju

Subbu works at Yahoo! developing standards, patterns and practices for HTTP web languages. In the past, he was a web service and Java developer. He was also a standards contributor at BEA and an author of books on Java EE. His current passion is HTTP and REST. Subbu confesses that he's not a web developer, has no interest in the internals of programming models used for web frameworks and he's only interested in the visible aspects of the architecture.

"The Web is Mostly Restful"

Being RESTful in an abstract sense means:

• Resources are named by URIs
• Resources have representations (Atom, HTML, JSON, XML)
• Resources contain contextual links to allow navigation of state
• There's a Uniform Interface

In the web today, some resources and URIs are personalized, but most are not. Some depend on sessions, but most do not. The consequence of a personalized UI with a non-unique URI is you cannot rely on browser caching.

The web is full of different representations (HTML, XML, JS, PDF, CSS, Flash). The problem with HTML is you can't tell links that you want a particular representation based of a link. The links are hard-coded to be a particular content-type. However, some media types on responses are ignored. This is often a problem with browsers and whether the user has plugins installed.

The Uniform Interface for the web is HTML and primarily links and forms (GET and POST). There's still some misconceptions (e.g. POST is secure). However, it's not about security, it's about idempotency and safety. You need to make sure you only use POST when you're changing data. POSTs are not repeatable. GET URIs are not always refreshable, which is quite unfortunate. Users shouldn't have to fight the back button.

Caching is a fundamental aspect of the web. Even in a personalized site, most of the content can be cached. The web is read-only for the most part. However, many enterprise web applications don't take advantage of caching. This is fine when there's not that many users, but it's bad when you want to scale to thousands of users. There's several frameworks that use cache-busting and prefer backend caching over HTTP caching. These frameworks are not using the web like they should.

Backend caching (e.g. Memcached) uses a non-uniform interface and you need to explicitly program to it. Frontend/HTTP caching has a uniform interface that's pluggable. Backend caching is generally more expensive to develop and deploy. There are cases where data should be cached on the backend, but you shouldn't focus all on backend caching w/o doing some frontend caching.

With Ajax, you get more opportunities to be RESTful. XMLHttpRequest is another HTTP client that can be programmed to. It has full support for the uniform interface, which allows content negotiation, optimistic concurrency and caching. Cross-domain hacks can be done with <script> and <iframe> to tunnel requests over GET. The W3C has been working for the last two years on how to do cross-domain Ajax w/o using hacks. The problem with current cross-domain implementations is they often use GET for everything, which isn't very RESTful. Subbu recommends using a proxy on the same domain if you do need to talk to other domains. This will allow your Ajax code to remain RESTful.

Web Frameworks
Web development is hard because of all the moving pieces that exist. Because of this, many web frameworks have been created to solve the various problems. In 1997, there were servlets. They provided basic plumbing and closely reflected HTTP/1.1. Servlets provided a poor programming model, but it allowed a lot of frameworks to be built on top of it. We don't use servlets to write applications, only to write application frameworks. The second era came about in 2001 when Action-oriented frameworks became popular. In 2004, JSF and friends came to play. JSF is a component-based framework with known limitations (complex, slow, uses POST for almost everything, Ajax is difficult). These limitations have resulted in a number of third-party patches being developed to solve these issues.

JSF was designed to use the request to create a component tree that maintains state. Unfortunately, the state is not something the developer has control over. It's not the state of the application, it's the state of the components. The client's knowledge of the state is mentioned with a cookie and the server keeps the state in the session. The problem with JSF is you don't have a choice of state in your application - you can't write stateless applications like you can with servlets.

JSF uses overloaded URIs for its resources. When you have one URI with multiple representations, there's no way to tell how a representation was chosen. JSF's compromise is to allow client-side state saving. However, they do this by putting hidden field in the form and requiring POST for navigation.

JSF vs. REST
Basically, these two are at opposite extremes. JSF is focused heavily on a UI component model. The people that developed it misinterpreted how the web works and made some fundamental questionable choices. You can patch it, but you can not fix it.

Web 2.0 Frameworks
GWT is a cross-compilation based framework. You write Java to generate JavaScript (b/c everyone hates writing JavaScript). It mashes client and server code into a single source. These layers communicate using GWT-RPC. Typical RPC concerns do not apply since code generation handles coupling and the client is downloaded from the same application. GWT-PRC does POSTs to the server and uses HTTP like a transport layer. To be fair, GWT does allow you to use a RequestBuilder to use the web like it should be used. This class allows more control over HTTP requests, it supports GET and POST and it allows so-called RESTful layers (GWT-REST and GET-Restlet). GWT is focused heavily on ease-of-use, which is good. It's modeled after RPC and breaks the uniform interface and focuses on backend caching. Unlike JSF, GWT is fixable, but the community tends to use RPC instead of RequestBuilder.

SOFEA has a central promise of SOA. Business logic is a reusable service that changes less often. The presentation application calls those services and changes more often. The nice thing about this type of architecture is it allows a separation of concerns and loose coupling. However, it doesn't embrace REST like it should. Appcelerator is an implementation of SOFEA that has a Ruby on Rails-like usability. However, it uses a SOAP/HTTP style with messaging and POSTs to a single URI. Appcelerator is interesting, but it introduces a different style of coupling. It breaks URI opacity and client deals with POX instead of links.

Conclusion
Don't fight the architecture of the web. Innovate and enhance instead of breaking. If nothing else, break judiciously. As developers, we should demand more from our frameworks and make sure they use the web and HTTP like it should be used.

Applying Flash to Java: Flex and OpenLaszlo with Dustin Marx

If you're going to choose Flex or OpenLaszlo, chances are you're targeting Flash. The Flash Player allows you to abstract the browser idiosyncrasies and give users a better experience. It hides the browser quirks from both developers and users. It's also a highly ubiquitous web browser runtime environment. It provides a user experience way beyond traditional HTTP request-response. Also, its visual effects and "richness" rival of non-browser desktop applications.

Mark's blog stats show that 95% of readers are using Flash 9 and 1% is Flash 10. All others don't have their version exposed. Most other sources claim that Flash 9 has 98% penetration in mature markets. One of the nicest things about Flash is it frees users from limitations of traditional web applications. Request/response is largely a thing of the past and Ajax-like behavior was built-in from the beginning.

Flash Criticisms: has reduced SEO as well as bookmarking and URL history support.

Flash Player Criticisms: not open source, no significant alternative, no 64-bit player, loading performance and it's only useful for games, movies and annoying advertisements.

The good news is Flash is getting better. There's currently a SWF Searchability initiative with Google and Yahoo!. For bookmarking and URL History, you can use "deep linking" with mx.managers.BrowserManager and mx.managers.HistoryManager. Flash Player issues are also being addressed. There's a Flash Open Screen Project, there's a 64-bit player in Adobe Labs and Flash 9/10 is much better than in the past.

To prove that Flash is a compelling technology, all you have to do is look at Microsoft's Silverlight and Sun's JavaFX. These are direct competitors that are fairly new and prove that companies like what Flash has.

Flex
Flex is not Flash. Flex requires Flash (9+), but Flash does not require Flex. Flex is a language and framework and applications are compiled into .swf files. Flash is the runtime environment that executes .swf files. Flex 3 is FREE. The Flex SDK, compiler and debugger are open source. They have no license costs. BlazeDS is also open source and has no license cost.

Flex MXML was formerly called Macromedia XML. It's an XML-based presentation/layout language that's editable with any text editor or IDE. MXML is to ActionScript 3 as JSP is to Java. MXML provides the layout and ActionScript provides the dynamic business logic.

ActionScript
ActionScript is an ECMAScript implementation that's been proposed as the Edition 4 implementation. It's not your older sibling's JavaScript. It uses class-based object-oriented features and static typing. Thanks to the Flash Player, it works the same across multiple browsers. Most of the things you can do with MXML, you can do with ActionScript. However, MXML typically requires less LOC.

ActionScript allows packages, interfaces, inheritance, objects and methods. It includes extensive XML Support, particularly E4X (ECMAScript for XML). It has a large class library and can talk directly to the Flash Player. Finally, it has many Java-like features and it's syntax looks similar.

At this point, Dustin started doing demos of two popular Flex components: RichText Editor (which creates horrible HTML) and Data Grid. More third-party Flex components seem to appear every day. Examples include flexlib, ASDIA as well as all those listed on FlexBox. Additionally, it's not too difficult to create your own Flex components (no proof provided).

Flex's property binding is one of Dustin's favorite features, but he says he has a difficult time conveying how cool it is. Property binding allows you to tie data in one object to data in another object. Updates in one object affect another. To use it in MXML, you can use curly braces or the tag. In ActionScript, you can use the BindingUtils object. You can also use Flex's metadata annotation "Bindable" to denote bindable objects.

To compile Flex applications, you can use mxmlc from the command line. You can use Ant with the <exec> task or using Flex's Ant Tasks. You can also invoke mxmlc from Java as long as you include mxmlc.jar in your classpath. FlexBuilder is an Eclipse-based IDE that's not included with the free Flex SDK. It's not a free product and can be used as a plugin or a standalone IDE.

Flex and Java
There's two predominant out-of-the-box methods for Flex to communicate with Java EE backends.

• HttpService: traditional HTTP request/response.
• WebService: SOAP-based Web Services.

If the above two methods aren't fast enough, you can use BlaseDS and it's additional options.

• Web Messaging: HTTP publish/subscribe with JMS, ColdFusion and/or other Flash/Ajax client.
• Remoting with AMF: access server-side objects from Flash client-tier as if they were hosted there.

Flash applications can access either a client's machine or a remote site, but not both. You can use a crossdomain.xml file on your server to allow remote Flash clients to connect. This file allows access for both Flex and OpenLaszlo applications.

BlazeDS adds proxy server support for HTTPService and WebService. To use, set the useProxy attribute to "true". Features include authentication and logging. It adds a new RPC mechanisms called RemoteObject. This object allows ActionScript and Java EE transparent integration. It also adds publish/subscribe messaging with a JMS Adapter available. Lastly, it adds Ajax support to your Flex application.

GraniteDS is an open-source (LGPL) alternative to Adobe LiveCycle and is similar to BlazeDS. It has COMET-like functionality and supports Spring, Spring Security, EJB 3, Seam and Guice.

Flex Frameworks: Cairngorm (Adobe Consulting), Pure MVC, Mate and many others.

Flex 4 (Gumbo) will have improvements for designers (easier customization, better tool support), improvements for developers (faster compiler, two-way data binding) and will leverage new features of Flash 10.

OpenLazlo
OpenLaszlo 4 is XML-based and uses an XPath syntax for data access. OpenLaszlo was actually created before Flex and is ECMAScript-based. Unlike Flex that requires Flash 9, OpenLaszlo is architected to deploy on different runtime environments, including: Flash 7/8/9 and DHTML. Dustin believes OpenLaszlo would be a lot more appealing if your source code could be compiled into Silverlight or JavaFX.

OpenLaszlo's syntax looks a lot like Flex, except it does not use namespaces. OpenLaszlo's Constraints are similar to Flex's property binding, except the syntax is a bit different. You use ${} in LZX tags or applyConstraint() and LzDelegate in scripts. OpenLaszlo's event handling is similar to Flex and JavaScript event handling. All attributes have an implicit "on" event that is triggered when an attribute's value is changed. Event handlers can be written CSS-style in LZX nodes or using the <handler></handler> tag. Script code can be embedded in LZX XML in many ways:

• Inside event attributes
• Within <script></script> tags
• Within <method></method> tags
• Within <handler></handler> tags
• In a separate file (<script src="someFile.js" />)

Dustin believes the debugger and view-source tools in OpenLaszlo are much better than the ones available for Flex.

For the rest of the presentation, Dustin covered many of Laszlo's feature, how they relate to Java as well as how to integrate SWF and HTML. SWFObject is Dustin's preferred method for adding Flash to HTML. One of its nifty features is it allows SWF-to-SWF communication.

This talk was an excellent and in-depth overview of Flash, Flex and OpenLaszlo. I especially liked all the details on ActionScript and the different methods for remote communication. Nice job Dustin!

The Colorado Software Summit and Spring 3.0's SVN

In a little over two weeks, my favorite conference begins in Keystone, Colorado. The reason I like it so much is because it's an annual gathering (this will be my 4th year) with friends and it's somewhat like a vacation, except you get to learn a lot. This year I'll be speaking about Appcelerator and Spring 3.0.

A few weeks ago, I wondered How open source is Spring and expressed my frustration in not being able to find the source code. At almost the same time, SpringSource's controversial maintenance policy was announced. Developers booed, Free Spring was founded and SpringSource changed their tune. In addition, someone sent me the FishEye URL for Spring 3.0's SVN. From that, I was able to figure out how to get Spring 3.0's source code.

svn co https://src.springframework.org/svn/spring-framework/trunk spring-3.0

The only bad news is FishEye shows the last change as "17 September 2008 ... (21 days ago)". If Spring 3.0 M1 is supposed to be released any day now, you'd think there would be more SVN commits. Anyone from SpringSource care to comment?

Appcelerator with Matt Quinlan

This evening I attended the Denver Open Source User Group meeting where the Basic Concepts talk was on Appcelerator. Matt Quinlan (Twitter, Blog, LinkedIn) was the presenter. I arrived 10 minutes late, so I didn't hear any of the intro stuff. Below are my notes from the event.

The Appcelerator developers liked the "onclick" syntax, but found it was too limited to do everything they wanted. Rather than onclick, they use an on attribute. For example:

<div on="click then l:show.box">
Click me
<div>

"DOM Manipulation is JavaScript cruft."

Appcelerator allows you to implement the Observer pattern in the browser. In addition to allowing DOM elements to subscribe to messages, server-side objects (in any language) can subscribe as well. In Appcelerator syntax "l:" means local and "r:" means remote. The messages that are passed to the server are JSON and have payloads. JSON is more popular than XML because you can eval() it and create JavaScript objects from it. Appcelerator allows you to do Declarative Ajax. On the server-side, you can annotation Java and C# classes with @Service to subscribe to messages. In other languages (i.e. PHP), Javadoc-style comments are used.

Tagline: The seamless fusion of RIA and SOA.

Web Expression Language
Goal is to eliminate 90% of the JavaScript you write. Example syntax:

on="[condition] then [action]"

Conditions include DOM events (click, focus, blur, change, mouse events), key events (up, down, press), other (history, drag/drop, selected, resize, iPhone orient, sortXYZ), subscribe to custom message. Actions include Scriptaculous effects (show/hide, fade, move, drop, grow), set element value (static, dynamic, bind), set CSS class or attribute, execute custom JavaScript, publish custom message.

Now Matt is doing a demo on http://try.appcelerator.org. This site consists of a form that allows you to type in Appcelerator code and run it. 3 attributes can be added to any tag: draggable, droppable and resizeable.

Client-Side
Add simple tags to your HTML to inject RIA widgets. Add single property to existing HTML elements for dynamic behavior. Eclipse Plugin built on Aptana, but is generally targeted towards web developers moreso than business analysts (no drag and drop of widgets).

Server-Side
Server-side development done with your IDE of choices. Based on your server-side tehchnology platform. Easily create services using annotations.

App Command
The app command is similar to Rails' GEM command. Allows you to build scaffolding and deploy to cloud (AppEngine, Amazon S3). It also allows you to pulldown components from the main server and auto-updating.

Examples:

• appTunes: widget that wraps Flex Cover Flow widget
• Snapshot: photo editing application
• Radio Javan: Persian music online
• SkyBlox: wireless company

Appcelerator allows you to create prototypes easily by using a JavaScript file with mocks for the server-side objects. In the next version, you can "annotate" the UI and allow end-users to Ctrl+Click on elements and add feedback. For an example of this, see http://dev.appcelerator.com/pearson.

When starting with Appcelerator, you can start by crawling (including appcelerator.js for widgets) then move to walking (decouple server-side and client-side) and finally running (developing working prototypes with mocks for server-side).

"Let's face it, ASP, JSP, PHP and Ruby are just lipstick on CGI."

Ajaxified Body

I've often wondered if it was possible to use Ajax to reload the main content of a web application without reloading the header, menu and footer. SiteMesh allows you to move these common elements to a decorator that gets wrapped around each page. Below is a diagram of how SiteMesh works.

You can read the Introduction to SiteMesh article if you're interested in learning more about SiteMesh's basic features. By default, SiteMesh decorates text/html responses and ignores any other content type (e.g. image/gif). It also contains an <excludes> configuration element that allows you to turn off decoration when a URL matches a certain pattern. For example, the following allows you to disable decoration when "ajax=true" is passed in the URL.

<excludes>
    <pattern>**ajax=true</pattern>
</excludes>

To optimize the loading of an application so the common elements aren't loaded for each page, it should be possible to create an Ajaxified Body where the primary content area (PCA) of the site is loaded via Ajax rather than refreshing the whole page. The header, footer and navigation bar often stays the same from page-to-page, so it doesn't seem to make a whole lot of sense to load them each time the page loads. The image below shows the PCA (of an AppFuse Light application) as a grey square with a red border.

Implementing an Ajaxified Body consists of the following steps:

1. Adding SiteMesh and moving common elements to a decorator.
2. Remove common elements from each individual page (if you're using includes).
3. Configure SiteMesh so decoration is disabled when the requested URL contains "ajax=true".
4. Write JavaScript that modifies all <a href=""> links (and buttons with onclick='location.href') in the PCA to have an onclick handler.
5. The onclick handler should call a JavaScript function that loads the link's URL + ajax=true using XMLHttpRequest (XHR).
6. Add XHR success handling to replace the PCA with the loaded content.
7. Add XHR error handling to go to the URL normally when response.status != 200.
8. Inspect the response HTML for <title> element and replace document.title if exists.
9. Inspect the response HTML for <head> element and append to current if exists.
10. Inspect the response HTML for <script> and <link> elements (JavaScript and CSS) and evaluate them if they exist.

As a proof of concept, I created a prototype using AppFuse Light (Prototype/Scriptaculous for Ajax). You can see a demo at the following URL. You can also download a patch or the source for this project.

http://demo.raibledesigns.com/ajaxifiedbody

Below are a number of things I discovered while writing this prototype:

• The hardest part of implementing this seems to be coding the exceptions. It's possible you'll have some links with existing onclick handlers and you may have to disable "ajaxifying links" for those links.
• A progress indicator is important or the page might load so fast that the user doesn't visually detect it changed. This can lead to a worse user experience because they don't see the flash of the blank page they're used to when a page load occurs.
• While forms can be submitted via Ajax, there's no harm in leaving existing form behavior in place where the full site is reloaded after submitting a form.
• If a particular page needs to change the common elements (header, menu, footer), it should be possible to do that with JavaScript after the PCA content loads.
• If the success/error indicator is outside the PCA, it may need to be populated and displayed/hidden with JavaScript after the PCA loads.

I'm sure my implementation can be improved, but I'm also curious to see what you think of this idea. I know it's not revolutionary, but it's something I'm considering adding by default to AppFuse and AppFuse Light. Do any Ajax frameworks do something like this out-of-the-box?

Update: Thanks to everyone for the great feedback - keep it coming. I agree that adding history support is a must. I'll try to do that in the next day or two. This post has also been featured on Javalobby and Ajaxian.

Update 2: Added history support.

RE: How Open Source is Spring?

Peter Mularien has a very well written post titled How Open Source is Spring?: An Analytical Investigation:

This post is to expand on some of the thoughts I posted on the SpringSource Blog in response to Rod Johnson's excellent description of the SpringSource business model and its commitment to development of open source software.

Now that SpringSource has shown an ability to crank out new product releases on a seemingly weekly basis, I wanted to reflect on where Spring is positioned in the Java open source community, and how open the Spring Core project is to work done by the public.

The hypothesis of my experiment occurred to me when I happened to be reviewing Spring JIRA assignments one day. I was curious whether, following the bug assignments, the majority of development on the "Spring Core" projects (including Spring MVC and what we would consider "classic Spring") is performed solely by SpringSource employees.

Peter's post is near and dear to me because I'm doing a What's coming in Spring 3.0 talk at the Colorado Software Summit in October. The only information I was able to find on Spring 3.0 is from random blog posts and Juergen's presentation. When I give talks about technologies, I prefer to dig in and try them before talking about it. With Spring 3.0's source code nowhere to be found, this is very difficult to do.

I really hope Spring 3.0 becomes available in early October. If it does, I hope to upgrade AppFuse, AppFuse Light and Spring Kickstart. If it doesn't, my talk will most likely be a regurgitation of what Juergen's slides have and that's just not right.

Happy Birthday Jack!

Jack's birthday was last Thursday (August 28th) and only now am I getting a chance to wish him a Happy Birthday on this blog. I told you it was a busy week last week.

Happy Birthday Jack!

On his birthday, I picked him up from Kindergarten at 11 and let him run the show for the day. Needless to say, we had a good time.

On Saturday, we had a party to celebrate at my house. It was a great time with many old friends and lots of crazy kids.

I woke up to quite the disaster area the next day. I was also quite impressed when Abbie showed up with her ears pierced.

The rest of the weekend I spent quite a bit of time enjoying A Taste of Colorado. When work began on Tuesday, the week intensified as I was the "Release Owner" for LinkedIn this week. We made a number of backend changes to reduce statefulness and improve performance. I'm proud to say it was one of the smoothest releases I've been a part of, mostly because of the high quality people involved.

As far as my schedule for the rest of the year, it seems like I'm going to be busier than ever. I have to complete my presentations for CSS this week. In two weeks, I'm speaking at the Colorado Springs Open Source User Group Meetup. The following week I'm heading to Munich for Oktoberfest. If I live through that, I'll be implementing Memcached, speaking at CSS, hunting with my Dad, celebrating Abbie's birthday, traveling to Costa Rica/Panama and keynoting the JavaEdge Conference in Israel. If you happen to be in Colorado Springs, Munich, Mountain View, Keystone, Montana, Costa Rica, Panama or Israel in the next few months, maybe we can enjoy a beer together. Cheers!