2008-10-12
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Surveying open-source AJAX toolkits
Packages from Dojo, Zimbra, Yahoo, Microsoft, Google, and
OpenRico/Prototype showcase the variety of libraries available to AJAX
developers
By Peter Wayner
July 31, 2006
If you want to add AJAX to the magic collection of buzzwords supported by your Web site (and who can resist the siren
call of the latest buzzword?), then you have two major options: purchase a proprietary package or experiment with open
source libraries.
InfoWorld has covered a number of excellent proprietary AJAX toolkits in the past, and now we’re turning our attention to
some of their open source rivals. Are they worth exploring for enterprise use?
[Watch AJAX screencasts: Dojo, Google, Microsoft Atlas, Rico, Yahoo, Zimbra]
The open source toolkits I examined span a wide range of what might be covered by the term AJAX, an acronym for
Asynchronous JavaScript and XML that began appearing little more than a year ago. The idea of using JavaScript with or
without XML to add intelligence and interactivity to a Web page dates from the earliest days of the Web, and AJAX is now
one of the best ways to distribute client applications with a minimal amount of fuss. (See more on the intricacies of AJAX.)
If you’re interested in whether these open source packages compete with the best commercial tools, the simple answer
is: not in general but sometimes in specific details.
The best-known proprietary packages, such as Backbase, JackBe, and Tibco's General Interface, all offer complete
development environments with full toolkits, sophisticated event models, and debuggers. With them, you can write
applications that run in the limited environment of a Web browser but offer almost all of the features of native code. (See
more on proprietary AJAX tools we've reviewed.) None of the open source packages I looked at come close to the range,
depth, and support of these commercial packages.
But that doesn’t mean that there isn’t plenty that’s worthwhile in these open-source AJAX projects — there’s an explosion
of interest in the area right now.
Selecting the six
Passing over dozens of excellent packages and thousands of perfectly adequate solutions, I selected high-profile toolkits
supported by the most stable organizations: Dojo, Google Web Toolkit, Microsoft Atlas, Open Rico and Prototype, Yahoo
AJAX Library, and Zimbra’s Kabuki AJAX Toolkit. Microsoft’s Atlas may not be open source — the license includes terms
that would rankle a devotee — but the code you create with the system is yours to license as you like, and you’ll be able
to create Atlas apps with few practical restrictions.
The six packages I examined all offer a number of extremely useful user interface widgets and background tools for
simplifying the process of building an AJAX application. They will be most interesting to developers with running
applications who only want to add a new part or update a page. If you want to add an animated panel or a live table, for
example, you can usually cut and paste them into place; the examples are generally good enough to help you
accomplish the basic routines.
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Still, there’s often a need to fidget and fuss with the code if you want to do things that are even slightly different from the
established framework. It’s a feeling that will be familiar to most programmers who have used open source: The code is
often quite nice, but the developers seem more interested in getting it out the door than re-engineering it until it’s even
easier to use.
For instance, with some of these tools it took me just a few minutes to add a table of data that could be sorted on the
client — if I imitated the example code as closely as
humanly possible. But if I tried to improvise or do
something differently, the code would break, and the
documentation was often quite unhelpful.
This rough surface means that any development team
should think about its environment before putting open
source AJAX tools into action. If you have seasoned
programmers and the ability and time to use the freedom
and flexibility provided by the source code, these toolkits
are great deals. If you’re a newer programmer or
someone without the time to wade into a project, you
should think twice about the costs and consider the more
professional packages.
Dojo
If there is one open source AJAX project that is leading the pack these days, it might be Dojo. It’s not necessarily better in
any particular way than the others, but it is both broad and deep with a big selection of very customizable widgets. These
traits may explain why both IBM and Sun have recently signed on to support the Dojo Foundation and its work.
The project Web site and the code have the flavor of an exceptionally fertile open source project run by a neutral team of
enthusiastic developers. The management is clearly aiming to encourage a wide range of contributions — as long as
they fit Dojo’s basic philosophy demanding simplicity and clarity.
Dojo has an excellent editing package, a wide selection of animating boxes, some drag-and-drop tools, and much more.
A tool for providing maps from Google and Yahoo just appeared in the latest 0.3.1 version.
I feel, however, that Dojo suffers a bit from the kitchen-sink-like quality of popular open source projects. Some parts of the
library are well-documented and illustrated by a set of good demo pages. Other parts have little documentation, leaving
developers on their own — the manual as well as the book describing the project have large holes typical of
volunteer-built documentation.
Adding a bit of the Dojo toolkit to your Web application is pretty easy. The source code is modular, so your application
only needs to load the necessary pieces using Dojo’s loading mechanism. In many cases, all you need to add is an extra
attribute, dojoType, to your working HTML, and the code will do the work when it loads the page.
Dojo continues to improve as it attracts more developers with more ideas and code from other projects. The leaders are
doing a good job of keeping these contributions in order, and there’s every reason to expect more sophistication in the
future.
Zimbra Kabuki AJAX Toolkit
When Zimbra appeared as a complete solution for offering e-mail and calendar management to an office, many were
impressed by the package’s sophisticated use of AJAX at all levels. Every widget was designed to have a real live feel. Although the entire suite of tools is available under a community source license, Zimbra chose to spin off its Ajax toolkit in
a separate package called Kabuki that’s licensed under either Apache or Mozilla. The toolkit includes some of the
practical tools and widgets but not all of the pieces found in the larger package.
That doesn’t mean Zimbra’s toolkit comes up short, though: Kabuki has an excellent editor, a nice tree package, and a
layout mechanism that can be used to build sophisticated user interfaces.
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Zimbra’s system doesn’t have the same polish or
sophisticated animations as Dojo or Yahoo’s AJAX
package. The widgets are quite functional, but they’re
also fairly basic; there’s no sign of the sophisticated eye
candy some people expect to see when they start using
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some good design, but it’s going to take some extra
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Zimbra AJAX mechanism is still filled with largely
practical tools.
Google Web Toolkit
The oddest toolkit in the batch may be Google's.
Whereas the others are written in JavaScript and meant
to be integrated into your own JavaScript code, Google’s
Web Toolkit is written in Java itself and translated into
JavaScript. When you write your code, you write Java
and watch it get translated into JavaScript.
This isn’t as magical as it sounds because JavaScript is
pretty close to a superset of Java, at least in a cosmetic
sense. It’s not complicated to strip away some typing
information from the Java code and end up with
something that resembles JavaScript.
The translation is, however, a fascinating solution and
one that Java programmers will both like and worry
about. I found myself fretting over questions about when
JavaScript will behave a bit differently than Java —
something that I don’t do very often.
The breadth of the toolkit is solid. Google has built in many of the standard widgets but hasn’t included some of the
flashier mechanisms for animation.
I found Google’s system surprisingly easy to use — it ended up being close to working with a fancy version of the AWT
(Abstract Window Toolkit) or a simpler version of Swing. The package is designed to build a full application that runs
inside the browser, not just add a bit of zip to your flat pages.
Open Rico and Prototype
One of the more prominent, pure open source AJAX
projects is made up of a loosely knit coalition of projects
including Open Rico and Prototype. Whereas Dojo is a
single big, unified project, these two and a few other
smaller projects are all technically independent.
It’s anyone’s guess whether this loose bond is better or
worse politically, but the results are just as impressive as
those of the other libraries.
Rico and Prototype share more of an emphasis on
animated effects and less on some of the pragmatic
tools. For example, there’s no tree and no emphasis on
collecting data from a form, but the animated effects and
the larger tools — like a set of accordion panels — are all there.
The Prototype library is a set of basic, low-level tools aimed at programmers. It has clean, simple functions, all given
single-letter names to speed downloading. It’s more of a shorthand for the common functions, and one you might want to
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adopt for your own code regardless of whether you use the larger mechanisms because it’s a disciplined approach to
writing smoother, simpler code.
Rico is a collection of some of the popular Ajax widgets and animations built on top of Prototype. You don’t need to use
Rico with Prototype, but it does make building AJAX apps simpler if you want the effects they offer.
I especially liked Rico’s LiveGrid, a set of routines that enhance an HTML table by fetching data in the background as
you scroll through the rows. It simplifies displaying a large volume of data in a small set of rows without forcing the user to
load page after page. I often think of Rico as a smaller, simpler version of Dojo that does a few things better than Dojo,
such as enabling drag-and-drop support.
Microsoft Atlas
The software world is often divided into two groups:
Microsoft and everyone else. This is almost accurate
when it comes to JavaScript and AJAX. Microsoft helped
legitimize the space by creating some highly
sophisticated AJAX features, and it continues to innovate
with Atlas.
The Microsoft Atlas library may be free, but getting the
package is not simple for people who aren’t using
Microsoft’s Visual Studio. Microsoft is much happier if
you download hundreds of megabytes of development
tools before installing the Atlas JavaScript libraries that
handle the bulk of the work. You can’t really get at the .js
libraries without jumping through the hoops — I got
nowhere with my Mac.
The libraries themselves are a bit less demanding. They offer good cross-browser support for Firefox and Safari users,
something that may surprise Microsoft haters. But there are limits to even this commitment: I saw the phrase “Due to a
known issue with Atlas on Safari” several times in the documentation, and there were similar notes for Firefox users.
These notes, however, concerned relatively minor details such as whether a popup box vanished when someone clicked
outside it. The very fact that the notes are there is more of a testament to Microsoft’s commitment than an indication of its
failures.
Atlas’ collection of widgets is a bit sparse, at least compared with the other offerings; there are no big editors and only a
few animation tools. Much of the work is instead devoted to integrating the AJAX with the server, in this case the .Net
Web services. The documentation and the examples in these cases are excellent.
There are a number of mechanisms for taking information from the database and formatting it at the client. All of them rely
heavily on C# on the server, and all of them integrate well with the JavaScript on the client.
The code is clearly meant more as an extension of the .Net platform, not a tool for doing slick things on the client. If you’re
heavily invested in .Net and you want to leverage the system’s Web service infrastructure, Atlas is a good way to add
some life to your Web pages by consuming services there.
Yahoo AJAX Library
Yahoo’s AJAX library is not only a solid collection of functions but also a good illustration of how to publish open source
software. The code for adding a core group of widgets to your Web application comes in a zip file, and Yahoo offers a
wide variety of examples and design suggestions. Many of the routines come with six to 10 different examples, all with
sample code and demonstration pages.
This approach is markedly different from the other packages because Yahoo is just as intent on pushing a clear design
philosophy as it is on delivering a piece of code. This tactic is more important than it may seem because the general user
still needs a great deal of education about how AJAX applications behave. The designers at Yahoo want to push a
stable, consistent behavior for the AJAX widgets, and their very complete documentation encourages this.
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The collection of features in the Yahoo library is solid but
not as large as Dojo’s. It has many of the standard tools,
such as an animation library and a tree collection, but
there are few of the larger, more substantial tools such as
an editor or a live table.
Yahoo does add some nice touches. The animation
library, for instance, also interacts with some standard
tools, such as a text scroll device that allows you to
automate the behavior of some part of the HTML — say,
a box filled with text. The Connection manager will
automatically assemble all of the data from a form and
put it into the right format for a GET or POST application.
Despite the lack of an editor, these interactions give
Yahoo’s library a smoother feel, compared with the
rough-and-tumble state of Open Rico or Zimbra. Whenever you dive into the code with Yahoo’s toolkit, you usually come
away feeling that the company has spent a bit more time optimizing the functions and adding some real depth to the
libraries.
Opening up the future
As these open source AJAX packages evolve, I think we’ll see more of a difference between the ones that are directly
tied to one corporation and the ones that remain outside the control of one particular company.
I expect that Google, Microsoft, and Yahoo will continue to exert tighter control and editorial guidance over their AJAX
projects, compared with the neutral packages. This control will help people who like a bit more polish and better
documentation, because I expect that the vendors will include the efforts of regular staffers.
Such generosity always comes with a price, although it may be small. Yahoo’s JavaScript libraries, for instance, will
always be there to support Yahoo’s mapping business. Dojo’s libraries, on the other hand, can work with either Google
Maps or Yahoo Maps.
The neutral packages, meanwhile, are bound to grow more varied as they attract more contributions. Some parts of Dojo
are already ports from smaller open source efforts that were rewritten to use the core parts of the Dojo packages. I expect
that more people will work to add their few lines of code to these projects, if only because it will make it easier for them to
leverage the libraries with their own projects. The neutral packages will likely continue to be the ones that offer the most
creative ideas and the cutest widgets at the quickest rates.
This schism, however, is just a prediction. Dojo is now supervised by a foundation with support from major corporations;
perhaps it will start focusing its effort and polishing its documentation. And there is no reason why the bigger companies
can’t start nurturing and soliciting more contributions to their packages.
Regardless of how they evolve, the best way to use all of these open source packages is to pick and choose the parts
you need to assemble the Web application you want. For example, I eliminated Dojo’s editor from one of my projects
when its text editor didn’t offer access to the data in the format that made my life easiest — so I switched.
It’s difficult to suggest one particular library as best or to make blanket statements about superiority because so much of
the toolkits’ usefulness depends on your programming style and needs. I recommend taking a tour of each and even
mixing and matching the libraries. After all, there are few practical reasons why you can’t use code from Atlas and Dojo
on the same page.
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