Enhanced DTs Extract 1: Progress Dialog Worker Preview

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Here is an extract from an upcoming article, called "Enhanced DTs" about EDT "boilerplate" programming.
It starts off looking at moving your boilerplate sideways into a separate class, and then ends off using CGLIB's interceptor
mechanism (which CGLIB calls an "enchancer," hence the name of the article). On the way, we explore some other interesting EDT stuff like Foxtrot.

So anyway, this blog is an extract which is a preview - can you get any more noncommital than that?!

extract().start()

In addition to the standard SwingWorker we know and love, other convenient workers
built on this are popping up, eg. BackgroundWorker in
"Swing and Non Blocking JAX-WS",
and Task in Hans Muller's JavaOne2006 JSR296 slides.

Richard Bair's Web Swinging
presents SwingX-WS,
a beautiful and convenient API for Swing clients to access webservices - and plain
old websites, eg. to do some screen scraping, data mining, or whatever.
If you haven't read that article yet, drop everything right now! Seriously! They have even
implemented XmlHttpRequest for Swing clients, with an onReady listener.
It's seriously awesome.

When accessing resources and services over the network, especially the internet,
but actually any network, then background threading becomes a necessity,
ie. using SwingWorker. One can automate this, eg.
SwingX-WS will send the XmlHttpRequest in a background worker, which
later fires an onReadyState event to be PropertyChangeListener,
in the EDT.

But while our long tasks are running, what should we be doing, or more
likely not allowing? For instance, the button that launched that task should probably be disabled.
Because for example, hitting the "Get New Messages" button
repeatedly in rapid succession doesn't really speed up
the process of getting new messages from the
email server (apparently).

Maybe we want to block the whole application, or at least the current
panel, eg. using a modal dialog, or glass pane, while that task is executing.
We might want to support a progress bar, and a cancel button.
(See Kirill's great looking
"progress glasspane" on flamingo.dev.java.net.)

So maybe we want some enchanced SwingWorker's at our disposal to drop into our code, as in the following example, which uses
an enhanced worker of the blocking (modal) dialog variety, with a progress bar built-in for added convenience.

    <font color=#000099><b>protected</b></font> <font color=#000099><b>void</b></font> <b>refresh</b>() {
        refreshButton.<b>setEnabled</b>(<font color=#000099><b>false</b></font>);
        <font color=#000099><b>try</b></font> {
            DProgressWorker&lt;ListModel, String&gt; worker = <font color=#000099><b>new</b></font> <b>DProgressWorker</b>(
                    <font color=#000099><b>new</b></font> <b>DDefaultProgressDialog</b>(frame, <font color=#99006b>"Simulating long task"</font>, <font color=#000099><b>true</b></font>)) {
                <font color=#000099><b>protected</b></font> Object <b>doInBackground</b>() <font color=#000099><b>throws</b></font> Exception {
                    <font color=#000099><b>for</b></font> (<font color=#000099><b>int</b></font> i = 50; i &lt; 100; i++) {
                        <b>taskProgress</b>(i);
                        <font color=#000099><b>if</b></font> (i%10 == 1) <b>taskInfo</b>(Level.INFO, <font color=#99006b>"Mmmmm.... "</font> + i + <font color=#99006b>"st donut"</font>);
                        Thread.<b>sleep</b>(50);
                    }
                    <font color=#000099><b>return</b></font> <font color=#000099><b>new</b></font> <b>DefaultListModel</b>();
                }
            };
            ListModel listModel = worker.<b>get</b>();
        } <font color=#000099><b>catch</b></font> (DCancelledException e) {
            logger.<b>warning</b>(e);
        } <font color=#000099><b>catch</b></font> (Throwable e) {
            dialogHelper.<b>showExceptionDialog</b>(e, <font color=#000099><b>null</b></font>);
        } <font color=#000099><b>finally</b></font> {
            refreshButton.<b>setEnabled</b>(<font color=#000099><b>true</b></font>);            
        }
    }
}

I'll leave the blow-by-blow discussion of its implementation for a follow-up article, but here is a sneak
preview...

(Progress Worker Demo, 110k/440k, unsandboxed, Java5)

You'll see that we introduce a "task listener" with which we construct our "progress worker." The worker publishes its current progress to the task listener, which in this example is a dialog with a progress bar and what-not.

With a voiceover to go with it...

(Progress Worker Walkie Talkie, mp3, 12Mb, 12minutes)
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Here is a screenshot of the demo running.

The next part of this "mini-series" will look at using this progress worker in a nonblocking fashion, where it publishes the progress to a status "mini-bar" at the bottom of the frame.

postscript()

Incidently i've been evolving a GUI "framework" which i'm using for these WebStart demos, and writing an article called GooeyBeans, with some beans binding and configuration and what-not. I did a bunch of stuff yesterday till all hours which got me to waking up this morning realising that so much of that software and article is actually rubbish.
Gutting. But i am happy that it's gonna be
much better than it is. That's what R&D is all about, making rubbish so that you don't make rubbish.