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At the end of the day, how do you implement scalable multi-threaded continuations? Yes the code has a better allure, but it's not exactly hard to add parameters to http requests.

Having used a few frameworks, I can tell you it's also easier to debug code that's closer to http requests. Being able to simply look at what's being passed in a simple way and understand everything instantaneously is a big advantage. Actually, this argument is more about the tools at hand, but there are definitively more and better tools to analyze http requests than anything else.

yea I hear you. The problem I have will passing the http parameters is that it only goes one level deep. If you want to nest it arbitrarily you would have to build up a comma separated list of values to refer to all the places you need to return to. At that point, if you think of this list of return places as a set of pointers it is as if you are implementing a stack. Having this kind of thing as a first class construct could maybe allow this to be checked by the compiler.

To be honest the details of implementing 'scalable multi-threaded continuations' is beyond my skill level.

Yes scaling continuations based web apps can be a big headache. I think this is why the Seaside developers have been scaling back continuations and making them optional in the framework: http://lists.squeakfoundation.org/pipermail/seaside/2007-Dec...

Coroutines are an interesting lighter alternative (though will still suffer from threading & session affinity issues).

See coro based libraries/frameworks influenced by Seaside like Continuity (http://continuity.tlt42.org/) & Nagare (http://www.nagare.org/) (which I think uses coros?).

Here is a fulling working Continuity example:

    use strict;
    use warnings;
    use Continuity;
    use HTML::AsSubs;

    Continuity->new->loop;

    sub main {
        my $r = shift;

        ###########################################    
        # helpers

        my $update_billing_info = sub {
            return 1 if eval { $r->param('updated') };
            return;
        };
    
        my $display_update_billing_info = sub {
            $r->print(
                form(
                    input( {type => 'checkbox', name => 'updated'}, 'updated?' ),
                    br,
                    input( {type => 'submit'} ),
                    p( "No. of tries thus far - $_[0]" ),
                )->as_HTML
            );
        };
    
        my $render_checkout_screen = sub {$r->print("Updated after $_[0] submits!")};
    
        ###########################################    
        # business logic

        my $count_tries;
        while (not $update_billing_info->()) {
            $display_update_billing_info->( $count_tries++ );
            $r->next;
        }
    
        $render_checkout_screen->( $count_tries );
    }

You should look into Lift (http://liftweb.net). It has a lot of what you describe. Here's a getting started slide deck I gave last year:

https://docs.google.com/present/view?id=dcbpz3ck_24f3v83ggz&...

Why are you tied to Java? Is there something about Smalltalk that makes you not want to learn it or are there other constraints?

Well it is the main language that I have worked in for many years now. I did some Perl early on and have done small one off projects in Python and Ruby. I really like how rock solid the jvm is and then there is always Scala and Groovy (mostly Groovy).

Another thing is that in my personal programming the server side isn't really where I hurt the most. Currently I'm more interested in client side stuff. I am learning Flex and ActionScript at the moment in order to convert some code I did in javascript/ajax to Flex.

Recently a team won the DevDerby (" were challenged to create as usable and fully functional a program as possible in only six hours")

http://www.lmcalpin.com/post/1109835129/dev-derby-2010

They did it using the Play Framework in pure Java. Incidentally the Play framework supports Scala, but this example goes on to show that Java is'nt quite out of the game yet.

Have you looked at webflows in Grails? I believe it's using spring's webflow stuff, but is more grails/groovy-oriented, which might be easier to deal with.

have you looked into lift? It takes quite a few features from seaside, among others. And scala is much better to work with than java...