Ive been unable to sleep, of late, worrying about my ability to deliver a cutting edge, ajax enabled application from within Tapestry. I chose Tapestry as a framework before I had significant user experience, but after being utterly dissatisfied with the maturity of all other java component-based frameworks. However, the rewind cycle thing started to make me nervous as soon as I began to understand it, as a good ajax application really needs to be able to make requests back to the server that are independant of the content or structure of a page.
I really like Tapestry's templates, which alow me to retain the general structure of the raw html so I can work with designers easily, and the support for internationalization is excellent, but the page orientation of all client-server communication was making me nervous. I believe, from some of the reading I've done, that the Tacos components that make async requests actually cause a full rewind on every request. More importantly, I couldn't imagine how I would support doing things like adding new form elements from javascript. I think I came up with a solution last night, but I can't be the only person thinking about this problem, so I thought I'd run it past folks here before writing it up in full and starting work on it. AT the very least, hopefully someone will clue me in on the correct way to handle this if my solution has holes in it that I am unaware of. So please, bring on the constructive criticism. Also, bear in mind that I don't have a very deep understanding of Tapestry internals yet, and my first task will be to delve under the hood and figure out how I would actually proceed, so I may make the occasional factual error below. There are a number of available tools for marshalling/unmarshalling java objects to and from xml (or JSON or anything else. I'm fairly agnostic on this one). The only issue is how to submit requests to the server and get back results without having to be concerned with page structure or doing lots of unnecessary work. The thought I had was to add a second servlet to my webapp, one which functions in a tapestry-esque manner (injecting services and properties, autopopulating properties based on request contents, use Tapestry annotations, etc), but which is 'stateless.' The Service (as opposed to a Page) would have properties populated according to some known scheme (in previous projects, I've used jakarta BeanUtils notation, ognl, Maps, and other tricks, and then a listener method would be called. The listener would either return an object which could be marshalled back as XML/JSON/text, or would write directly to the client. Of course, it would be easy to provide custom marshalling mechanisms for any given class that might be returned. All that would be required would be javascript in the page which knows how to parse the incoming data. Now, it is entirely possible that something like this could be built within the confines of a Tapestry Page, perhaps by providing a new Service, so my concept of a second servlet stems mostly from ignorance of what is available to me, currently. Regardless of the implementation details, the resulting app would be quite compelling, for me, and I suspect for others. We would get Tapestry's excellent templates/internationalization/infrastructure but all data i/o would occur via Services instead of Pages. When Page changes are required, and for simple forms, Tapestry Pages would still be very useful, but much of the business logic could migrate away from the Page rendering logic. Obviously, you'd have to be careful of the rewind cycle when dynamically adding new input fields to a page which might get submitted, but even that can be handled by submitting the new objects asynchronously and then re-requesting the page asynchronously, getting the browser version and the tapestry state back in sync. At any rate, in a full ajax app, it is unlikely that form data would ever be submitted back via a regular post, so it is probably a moot point for many, if not most 'Web 2.0' apps. There, I actually used the term. Ugh. These are just brief ramblings, as I have to run out, and I wanted to get my thoughts out there before I am away froma computer for most of the day. So please, feel free to take my idea apart, as I am sure I'll learn plenty in the process. In the end, so long as I can do ajax-y things within Tapestry, I don't care how I get there. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
