Daniel Lopez wrote:
> Hi Drew,
>
> What you ask for shouldn't be too difficult to implement. If I had to do
> it, I'd use reflection, as you mentioned, and I'd just add a new field
> in configuration file to allow the user to specify the name of the
> method to be called. However, if you want the methods to be executed
> using one instance, then you should also add something to identify the
> instance you want to use for every operation. If you wanted to call
> methods that have parameters things could get much more cumbersome.
>
It isn't actually that bad. The Java Reflection API lets you dynamically select a
method name, and set up a list of arguments in an array. You do, however, have to
know how many arguments to send (and what types they are), which leads to the next
comment.
>
> On the other hand... do you think it is really necessary to call
> different methods in the same class?. If you store the bean in the
> session( or in servlet context) and each operations is a small class
> that gets the parameters and calls the appropriate method from that
> shared bean, things get easier and, IMHO, more cleanly separated.
> As you pointed out, this Bean that you keep between calls inside the
> same user session, fits pretty much into the definition of a session
> EJB.
>
> As I conclusion, I'll just say that I opted for the command pattern
> because it keeps the controller servlet, and the configuration file,
> simpler and because I prefer to have a set of simple classes that
> perform each one a simple operation than one, or more classes, that
> implement everything. I find this arrangement easier to understand,
> debug, and easier to work with, when you develop in group. But that's a
> matter of taste.
>
I chose exactly the same approach (all my commands are independent Action classes
that implement an Action.perform(HttpServletRequest req, HttpServletResponse res)
method. I made this choice for the same reasons that Dan articulated (boy, we
must be pretty smart :-). To avoid class creation overhead, I cache an instance
of each Action class the first time it is used, and just re-use the same instance
over and over again for subsequent requests to the same command. Now, I can code
my action classes totally independently of each other, and be pretty confident
there's no side effects from multithreading or other factors.
>
> Just my 2c,
> Dan
Craig McClanahan
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