A few nights ago, I converted one of my long-running, open source, Java libraries from its horrid, old-style Ant build to Maven, largely because of several advantages Maven provides:
- It manages third-party dependencies cleanly and simply.
- It allows me to publish my library in a Maven repository, so that others who use Maven can easily depend on my library.
- It’s the defacto standard Java build environment.
Those are powerful advantages. The dependency management, alone, is an incredible time saver.
Nevertheless, one day after making the Maven switch, I ditched Maven for Apache Buildr.
Why I dislike Maven
The title of this article is Why I dislike Maven, but that title is worth clarifying. There are aspects of Maven that are terrific. Its dependency management is excellent, and the Maven-imposed source code layout is clean and well organized. Because of that standard source layout, many Java projects have Maven POM files that are nothing more than a listing of dependencies; Maven figures out the rest automatically.
But Maven suffers from a few flaws that drive me nuts.
XML configuration sucks
XML is a decent enough syntax for data, but XML is a crappy configuration language. For one thing, XML is verbose. Take a look at this Maven XML fragment:
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You have to wade through a lot of extraneous characters to get to the meat of that configuration item, which is: the build source encoding is UTF-8.
Imagine the same thing in a more typical configuration syntax:
project.build.sourceEncoding = UTF-8
YAML would also be a better choice than XML:
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Those latter two formats are more readable, with less visual noise, than the Maven XML version.
A fully-loaded Maven configuration file–even a simple one-can look like a big, gray blob, with all that XML markup getting in the way of the actual semantics of the build file.
Maven is also declarative, but not procedural. If I want to augment Maven’s logic–say, introduce a new goal–I have to do it through a custom Maven plugin; I can’t just stuff some special procedural logic into my POM. If I have to copy some extra files, that’s a rather high bar to clear.
I’m not the only person who thinks XML sucks as a configuration language. A full decade ago, Terence Parr, author of ANTLR and StringTemplate, wrote an article entitled Humans should not have to grok XML. Among the many good points he made, he wrote:
I hope to convince you that humans should not have to write and grok XML. Besides the many existing standard special-purpose languages that provide superior interfaces, XML is about as far away from natural human language as you can get.
My argument is simple: Humans have an innate ability to apply structure to a stream of characters (sentences), therefore, adding markup symbols can only make it harder for us to read and more laborious to type. The problem is that most programmers have very little experience designing and parsing computer languages. Rather than spending the time to design and parse a human-friendly language, programmers are using the fastest path to providing a specification language and implementation: “Oh, use XML. Done.” And that’s OK, but I want programmers to recognize that they are providing an inferior interface when they take that easy route.
Parr outlines, very clearly, why XML is an inferior language for human-to-computer interaction.
Polyglot Maven has promise, since it provides a way to express Maven POMs in Groovy, Scala, Clojure and JRuby, among others. I’ll admit that I’ve only played with Polyglot Maven a little bit. However, Polyglot Maven is really just Maven, with language-specific syntaxes replacing the XML version of the POM. As far as I can tell, from reading and experimenting with Polyglot Maven, I still can’t escape Maven’s declarative nature very easily. I can’t, for instance, just add some new inline Scala code to accomplish some project-specific task.
Clearly, what I want is something with Maven’s dependency-handling power, but with an easy way to escape to a real programming language, in case I have to do some local, heavy lifting.
Yeah, but what’s my alternative?
There are alternatives to Maven, alternatives that still retain the power of Maven’s terrific dependency management and publishing capabilities, without shoving all that hard-to-read XML in your face.
In the Scala world, for instance, the defacto standard build tool is SBT. Using Ivy under the covers, SBT provides powerful dependency management, and it understands how to use and publish to Maven repositories. Most important, in all the Scala projects I’ve written (and there are more than a few in my GitHub account), I’ve never had to write a single line of Ivy or Maven XML. Not one. In SBT, specifying a dependency uses a simple DSL that’s far easier to read than Maven’s XML:
libraryDependencies <<= "org.clapper" % "javautil" % "3.0.1"
All the artifact information is there, without much extraneous markup getting in the way.
So, why Buildr?
While I use SBT heavily, in my Scala work, I wanted to keep things even simpler for anyone who might want to build my Java library. SBT can be complicated, for the uninitiated. Buildr is a little simpler. Buildr riffs on Rake, the standard Ruby build tool. Rake does a terrific job of hitting a very sweet spot. It provides a simple, easy-to-read internal DSL for specifying tasks and task relationships, but it allows you to escape to the full power of the Ruby programming language when you need to accomplish some out of the ordinary task (something that is annoying, and often difficult, with Maven).
The fact that rake is an internal DSL for a general purpose language is a very important difference between it and [tools like make and Ant]. It essentially allows me to use the full power of Ruby any time I need it, at the cost of having to do a few odd looking things to ensure the rake scripts are valid Ruby. Since Ruby is a unobtrusive language, there’s not much in the way of syntactic oddities. Furthermore since Ruby is a full blown language, I don’t need to drop out of the DSL to do interesting things–which has been a regular frustration using make and Ant. Indeed I’ve come to view that a build language is really ideally suited to an internal DSL because you do need that full language power just often enough to make it worthwhile–and you don’t get many non-programmers writing build scripts.
Buildr is very similar to Rake, but it adds Maven-style dependency management. Compare my library’s Maven POM with the corresponding Buildr configuration:
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Not only is the Buildr file simply shorter than the Maven POM, it’s easier to read and easier to customize. And, if I need to add a custom task, I can do so with ease:
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The power and usefulness of Maven’s dependency management cannot possibly be overstated. But, in 2011, I can’t see why I should use such a crappy configuration file format, especially when there are much better alternatives.