Python Rocks! and other rants 2004/10

Weblog of Kent S Johnson

When should I use classes?

A question beginners sometimes ask is, "Should I use classes in my program?" This article gives some ideas of when it is appropriate to introduce classes into a design.

Relief

It's such a relief to be coding in Jython again after working with Java. In Java I feel like I'm fighting the language and the APIs all the time. It's way too hard to get anything done. Python just does what I want with much less straining and fuss.

Aaahhh!

Sticky Widgets

A technique I am using quite a bit is to make sticky widgets - GUI widgets that autonomously remember some part of their state. For example, a text field that remembers its last value; a window that remembers its last size and shape; a file dialog that remembers the directory it last showed.

These widgets make it very easy to create a user interface with some persistent state. This saved state makes the GUI much easier on the users.

In my case the widgets are written in Java using Swing. Each widget takes a preferences key as a constructor argument. The given key and the class name make the full key. This allows the widget to save and restore its state without reliance on any application globals, and without writing any application code specifically to handle the stickyness. The widget registers itself as a listener to itself so it is notified when its state changes and it persists its new state.

This is work code so I won't post it but it is really pretty easy to do and very handy.

Spring Free

For my current project, a distributed application with a database back-end, I tried Hibernate and Spring. I really wanted to like them! They have lots of cool features and make some things incredibly easy. But in the end I have gone back to tried-and-true simple tools - Jython, Velocity, Jetty and not much else.

Hibernate felt like it got in the way as much as it helped. I was constantly having to figure out the Hibernate way of things. My data is largely a tree structure flattened into a database table. Hibernate's lazy loading was sometimes great and sometimes exactly wrong.

Spring just felt too big. Every time I needed a new piece I would have to add another Spring jar to my lib directory and usually a few more jars that it depended on. It felt like using a sledgehammer to squash an ant.

Java also feels quite cumbersome now. I have been working primarily in Jython for about a year now and I hate the hoops that Java makes me jump though to get anything done.

In the end it all felt too confining. I was Mech Warrior, high in a robot programming vehicle, directing awesome power from from my command post. But I longed to put my feet on the ground, pick up a light pack and run.

So I have chucked it all, salvaging what I can, starting over for the rest. What a relief it is!