Some of the questions you ask here are really more for you to decide...
there aren't any canned answers. That being said, I'll do my best...
To begin with, I highly suggest checking out the numerous articles on
AJAX out there to get a firm grasp on what it really is, and if I may be
so bold, start with my own:
http://www.omnytex.com/articles
This will show one way AJAX can be integrated with Struts. You can also
check out my AjaxChat example app on the Struts Apps SourceForge site:
http://struts.sourceforge.net
The short answer is that AJAX, generically, is nothing but an HTTP
request. As far as whatever is on the server is concerned, be it a
Struts apps or something else, it doesn't look any different than any
other request. Well, I suppose more accurately, it doesn't *have* to
look any different. If you simply pass simple parameters from the
client and forego XML, then to Struts there's no difference.
If you want to use XML and Struts, then you will at this point have to
do your own parsing. With Struts 1.3, it would be trivial to add a
Command to the processing chain to parse an incoming XML message and
translate it to request parameters... come to think of it, that exists
already:
http://sourceforge.net/projects/strutsws
Although that's for Web Services, the underlying theory is identical.
There is a 1.3 version, courtesy of Marco Mistroni, but you can see my
original version with the customized RP. The same thing would work
nicely for AJAX, although one can envision other ways of doing it too.
You could just as well have this function in your servlet... it's just a
matter of getting the body content of the HTTP request, which would be
XML, parsing it and doing what you'd always do. If this interests you,
have a look at the code in CVS HEAD here:
http://javawebparts.sourceforge.net
I'll probably cut a release this weekend, but the code in CVS for the
AjaxTags component in the sample app does exactly that... an AJAX
request is made with XML in the HTTP body, and a servlet in this case
gets it (via the handy RequestHelpers.getBodyContent() method) and then
uses Digester to parse it.
Everything I've talked about here is "naked" AJAX, i.e., without the
help of any particular library. AJAX is really quite simple, aside from
a few gotchas, but there are some very robust libraries that will help
with more than the basics in most cases. They all seem to have a
slightly different focus from one another, so if you'd prefer to go that
route, some (of the many!) to look at are:
http://javawebparts.sourceforge.net/javadocs/javawebparts/taglib/ajaxtags/package-summary.html
This is the AjaxTags component of Java Web Parts... this is a little
different than the rest in that it makes enabling specific events very
easy. All it requires is adding custom tags to your page, and
configuring various AJAX events via XML config file. For instance, if
you want to fire an AJAX event when a <div> is clicked, and then you
want a function that will populate another <div> from what the server
returns, this is a trivial exercise with AjaxTags, and it's all driven
by config file so there is no coding involved, aside from adding a tag
or two to your page. This is my own creation, so obviously I'll push it
a little more than the rest, but I truly do believe it offers something
than most other options do not and you probably should at least check it
out and see if it meets your needs.
http://dojotoolkit.com/
This is the one people are starting to really get behind, and from what
I can see there is good reason for it. This is one of the ones that
will give you more than just AJAX, and that might be very appealing to you.
DWR of course you already know about.
http://prototype.conio.net/
Prototype is actually more of a foundation as there are other libraries
that use it. So certainly check out some of those libraries, but
Prototype on its own might be something you want to use.
There is no canonical answer at present for integrating with Struts, but
the point is there probably doesn't ever have to be one... it's just an
HTTP request. Oh, there could be something added to Struts to handle
automatic parsing of XML and stuffing it into an ActionForm, that might
not be a bad idea, but since you have access to the request object
anyway in an Action, you can do everything that Struts would ever do for
you so it would probably be unnecessary to add it to Struts.
To the question of whether AJAX is appropriate or not... first, from a
security standpoint, AJAX is no different from every form you submit,
every window.location call you make, every image you GET, etc. The same
security concerns that arise in those instances are present with AJAX.
AJAX has a limitation in that it can't make requests to domains other
than the one that served the page it's on, so in a sense it's MORE
secure. But the bottom line is you secure AJAX the same way you secure
your webapps generally.
If your wondering if it's worth it, that of course is for you to answer.
There are some cases where it absolutely makes things better, but it
comes with some baggage... unless you spend a lot of time worrying about
graceful degredation, your app will now *require* scripting. This might
not be a problem for you, but it might be. AJAX is also a problem for
accessability. In some cases this is a major problem, but even when
it's not it's something we should all think about. It also raises the
level of expertise your app requires to maintain.
I'm personally a fan of AJAX. I've been doing AJAX for over 5 years
(keep in mind that AJAX is really more a philosophy and an approach than
it is any specific technology... I haven't used XMLHttpRequest for very
long, but I accomplished the same types of things in an app 5 years
ago). I believe the age of the "classic" web, where scripting is
optional and apps redraw entire screens, is dead. AJAX itself is
nothing knew, but the mindset that accompanies it largely is, so if your
asking *me* if its a good idea in the first place, I'd say absolutely
yes, assuming two things... first, that the way you want to apply it
makes sense; anything can be used in a pointless way of course!, and
second, that you understand and can accept all the caveats that go along
with it.
Hope that helps!
Frank
Sonali Kulkarni wrote:
So, does it mean that is it not a good idea to use DWR with Struts just as
yet?
If so, what would be the best way to integrate AJAX into our Struts
application?
Ours is a full-blown *financial* banking Struts application. Please also let
me know if it is a good idea to use AJAX in the first place, considering (1)
the security risks imposed, especially for a financial application (2) ease
of integrating AJAX with Struts. (some of the questions i have, for starters
are... how do i pass the request object from the javascript to my action
class method, ... how do i handle errors returned etc)
Thanks for your time! Any replies would be appreciated!
On 12/3/05, Frank W. Zammetti <[EMAIL PROTECTED]> wrote:
From the DWR web site:
http://getahead.ltd.uk/dwr/server/struts
Just reading through it quickly, that's just about what I would have
suggested too in terms of separating out core logic from Actions and
letting your Actions and DWR servlet call them as needed. There might
be some better approaches, but it sounds like the DWR team is looking
for those approaches themselves.
Frank
Sonali Kulkarni wrote:
Please suggest if there are any good links, or some working examples
that
explain how Struts could be integrated into the DWR (AJAX) framework.
Any
help would be appreciated. There is hardly any online support or
documentation.
Thanks!
--
Frank W. Zammetti
Founder and Chief Software Architect
Omnytex Technologies
http://www.omnytex.com
AIM: fzammetti
Yahoo: fzammetti
MSN: [EMAIL PROTECTED]
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Frank W. Zammetti
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Omnytex Technologies
http://www.omnytex.com
AIM: fzammetti
Yahoo: fzammetti
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