Monday, April 05, 2004

Ant Lessons Learned 

x180: Ant and XML Build Files

My friends Mike Clark and Glenn Vanderburg asked to me to write up my current thoughts on using XML as the build file format for Ant based on watching it being used by Java developers over the years. It's very educational, as well as very sobering, to have software ideas that you put into form used by tens of thousands of programmers every day. Let me just say that you learn a lot from the process.

. . .

In retrospect, and many years later, XML probably wasn't as good a choice as it seemed at the time. I have now seen build files that are hundreds, and even thousands, of lines long and, at those sizes, it turns out that XML isn't quite as friendly a format to edit as I had hoped for.

. . .

Now, I never intended for the file format to become a scripting language—after all, my original view of Ant was that there was a declaration of some properties that described the project and that the tasks written in Java performed all the logic. The current maintainers of Ant generally share the same feelings. But when I fused XML and task reflection in Ant, I put together something that is 70-80% of a scripting environment. I just didn't recognize it at the time. To deny that people will use it as a scripting language is equivalent to asking them to pretend that sugar isn't sweet.

If I knew then what I know now, I would have tried using a real scripting language, such as JavaScript via the Rhino component or Python via JPython, with bindings to Java objects which implemented the functionality expressed in todays tasks. Then, there would be a first class way to express logic and we wouldn't be stuck with XML as a format that is too bulky for the way that people really want to use the tool.

Or maybe I should have just written a simple tree based text format that captured just what was needed to express a project and no more and which would avoid the temptation for people to want to build a Turing complete scripting environment out of Ant build files.

Both of these approaches would have meant more work for me at the time, but the result might have been better for the tens of thousands of people who use and edit Ant build files every day.

Hindsight is always 20/20.

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