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<title>The Great Refactoring</title>
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<h2>The Great Refactoring</h2>
<h3>Why the change?</h3>
<p>What was so wrong with JSwat that brought on this big redesign?
Basically everything. The program was written under the assumption
that there would always be a graphical interface. Thus, many
shortcuts were taken in the design and implementation. In
particular, there was a lot of dependence on a class called
<code>MainWindow</code>. This was referenced by the
<code>Session</code>, most of the actions, and even some
commands.</p>
<p>The change was really brought about when a user named Jack
suggested to me that JSwat should support a console-only mode. This
intrigued me since I fancied the notion that JSwat was so well
designed that this sort of feature should be easy. Ha! It took
three weeks (well, really two) to change all of the classes to
support an arbitrary interface. The rest of this page outlines what
was done to make this possible.</p>
<h3>What had to go</h3>
<p>First, the <code>UIBuilder</code> class had to be replaced by
something more generalized for building any type of interface.
Second, the <code>MainWindow</code> references had to be replaced
with references to the new generalized class. The
<code>CommandManager</code> class had to stop managing its own
interface components, namely the text input field and key press
listener. The <code>Session</code> had to sever its ties with the
<code>UiBuilder</code> and <code>MainWindow</code> classes, as well
as all of the panels.</p>
<h3>How that was done</h3>
<p>All of these goals were achieved by the introduction of the
"interface adapter" class. This class would be
responsible for building and managing the entire user interface.
That meant building the main window, menu bar, tool bar, panels,
and handling source view windows. A new interface was written to
provide the basic API for the rest of the program to interact with
the user. This is called the <code>UIAdapter</code> and it has two
implementations provided with the primary JSwat code.</p>
<h4>GraphicalAdapter</h4>
<p>The <code>GraphicalAdapter</code> class builds out the usual
graphical interface that most JSwat users are accustomed to. It
makes the main window, menu bar, tool bar, and panels, as well as
handling the source view windows. It provides the mediators for
displaying JSwat messages, taking command input, displaying the
debuggee output, and entering debuggee input.</p>
<h4>ConsoleAdapter</h4>
<p>The <code>ConsoleAdapter</code> class constructs a very simple
interface. It receives typed input from the user via the
<code>System.in</code> input stream and displays messages to the
<code>System.out</code> output stream. It is a purely console-based
interface, much like the well-loved <code>jdb</code> debugger that
comes with the JDK. There are no panels, no dialogs, no toolbars,
and no source views. JSwat messages and debuggee output are both
printed to the same place as that is the only place to do so.
Sending input to the debuggee is made possible via the
<code>stdin</code> command, which sends its arguments to the
debuggee's <code>System.in</code> input stream.</p>
<h3>How this has helped</h3>
<p>Granted, most people are not going to rush out and use the
console mode of JSwat, but it has brought about necessary changes
in the program's design. The classes were too tightly-coupled
and inflexible for there to be any chance of future expansion. In
addition, it has made David Taylor's task of writing a plugin
for <a href="http://www.jedit.org/">jEdit</a> much easier. This, I
am sure, is something that at least some JSwat users can
appreciate. In the future, it will be much easier to write other
interfaces to JSwat, allowing for more widespread use and
acceptance.</p>
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