I think the approach is a valid one, but it's better addressed through things like the
Java Apache project's Server Pages
Foundation Classes (SPFC) project (http://java.apache.org/). SPFC lets you
programmatically construct an HTML page and
attach actions to links. As Craig points out the actions necessarily have to be
processed on the server side, so a new
request comes in to another JSP/servlet page with the action info embedded in the
request, and presumably the "event handler"
you set up gets kicked into action. I haven't really played with this, so YMMV.
FWIW, Apple's WebObjects app server works like this. It's a very different (to me, at
least) way of dealing with state on a
web site as it provides an abstraction isolating the developer from the raw HTTP
connection even more so than servlets do.
It would be interesting to define some custom jsp tags to encapsulate that behavior,
but my initial reaction is that it's
outside the scope of the spec.
Wes
"Craig R. McClanahan" wrote:
> Brad Neuberg wrote:
>
> > On Thu, 13 May 1999, Craig R. McClanahan wrote:
> >
> > >
> > > OK, in the case you cited as an example:
> > >
> > > <A HREF="somelink" jsp:onClick="bean.someMethod(event)">Look mah, a
> > link!</a>
> >
> > Here's how you would handle this. On the server side the line right above
> > would be converted into the following:
> >
> > <A HREF="somelink"
> > onClick="sendEvent(event,'bean.someMethod(event)')">Look mah, a link</a>
> >
>
> You can write this code directly in your JSP page as well ... there's no need for
>server-side translation support to get
> this far.
>
> >
> > sendEvent is a javascript function that would be inserted by the JSP
> > engine:
> > <SCRIPT>
> > function sendEvent(event, method_to_call) {
> > .... defined here
> > }
> > </SCRIPT>
> > The sendEvent javascript function sends a GET request to the server with
> > the following CGI query variables at the end:
> >
>?jsp_callmethod="bean.someMethod(event)"&jsp_eventid=event.id&jsp_eventtarget=event.target&jsp_eventsource=event.source
> >
>
> Ah, so it's really a JavaScript change that you're after!
>
> I don't see any existing mechanisms for JavaScript to directly do an HTTP GET --
>although you can do it by using
> LIveConnect (where supported) to talk to a Java applet that does it for you -- but
>again that's all client side stuff.
>
> Now whenever the user clicks on that link the server side program can
>
> > respond by doing some action; you could probably wrap this with the Event
> > pattern so that the server side object then receives an Event object
> > telling it an event has occurred (it would be a JSPEventListener).
> >
>
> Lots of people use applet->servlet requests for exactly this purpose. The applet
>sets up parameters that describe what it
> wants, sends an HTTP POST request to a data-serving servlet, and the servlet returns
>a stream of serialized Java objects
> (or whatever else makes sense for your app). Then, you can "LIveConnect" the
>results back to JavaScript. The HTTP
> request-response paradigm *is* an event-processing pattern already -- responding in
>the form of dynamically generated HTML
> is merely the most common usage.
>
> >
> > The sum result of all this is that you can truly start using HTML as your
> > user interface. I don't know about you but I'd rather be using HTML and
> > Dynamic HTML as my user interface than Swing.
> >
>
> I agree with the sentiment, and the desire to have the dynamic interaction
>capabilities *within* a page (although this
> idea works much better on an Intranet where you've got reasonable transport speeds)
>... I just don't see any need to
> modify JSP to get there.
>
> Craig
>
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