Adam Hardy wrote:
So struts marshalls the HTTP request params into a form bean and perhaps
validates them.
Also struts interfaces with the model when it calls business methods
from action classes.
But for Ajax requests then there is only ever one possible actionForward
(or 2 if you count a global error). I can't imagine there's ever any
need for doing different things with the data - it's (un)marshalled into
xml, right?
XML in AJAX is completely optional. The form the result of an AJAX call
takes is completely up to you... could be XML, could be JSON, could be
HTML, could be something entirely different that you make up.
There is just as much possibility of multiple forwards for an Action
mapping that services an AJAX request as one that doesn't... you might
have a single Action that really performs a couple of different
functions, resulting in a number of different snippets of HTML being
returned. In that case, you would still very likely want to use JSPs to
render those snippets, in which case you may well have a number of
forwards. What happens though is that conceptually, forwards are no
longer associated, necessarily, with page (or view) transitions. You
can *almost* view them as calls to some method that generates a final
result.
With AJAX, it becomes very natural to think in terms of services rather
than pages... many AJAX apps load one master HTML document at the start,
and from then on the changes to the views are just bits of markup that
get displayed, or data used to generate new bits of markup to be
displayed. Then, an AJAX call is really just a request for the server
to perform some service and send back a result, which may or may not be
directly displayed to the user. The transitions between views is
largely a function of the client (some say the C in MVC moves to the
client).
Frank
Adam Samere on 24/05/06 22:57, wrote:
I've recently used AJAX in some existing Struts applications making
use of AjaxTags http://ajaxtags.sourceforge.net/. The Struts
controller is still very much applicable, in that the Ajax requests
are made to struts action urls, the action subclasses then delegate
processing to business objects in the same way as we're used to, and
finally forward to a JSP for generating the output. The major
difference is the JSP's generate XML responses, rather than
HTML/XHTML. Essentially they return either a page fragment or an XML
item list of some type which is then parsed and stuffed into the
client side DOM using javascript for immediate display.
Adam Hardy wrote:
I have only a small knowledge of the Ajax frameworks out there and I
am trying to work out how much an Ajax app would depend on Struts.
I assume the view in an Ajax app is handled at the initial request by
a JSP with HTML and that afterwards every request from the browser is
XHR, ideally broken down on a per-data-item/list basis. The view HTML
is from there on in handled by Ajax. In that case the Controller part
of MVC would be managed entirely client-side.
Therefore all that struts would have to offer the app would be
Validator and perhaps a couple of other services.
Or am I totally wrong? Can struts offer the ability to manage the
Controller part of the app in such a way that the project could have
two views - one in Ajax and one in JSPs?
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Omnytex Technologies
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