The importance of Central

One of the selling points of maven is it’s dependency mechanism. You say what code you need, and maven makes sure it’s there for you. The magic behind this is called central. It’s a phenomenal collection of software (much akin to Perl’s CPAN).

This is useful enough that other projects have sprung up that also use central, like apache ivy.

Central also has source code jars (most of the time). This means it’s possible to jump from your piece of code seamlessly into 3rd party code that’s available on central. I can’t imagine getting up to speed with other people’s code anywhere near as quickly without this sort of facility available. Sure, the source is available, but is it a single click away from your code? Not likely. m2eclipse and NetBeans 6.7 make this trivial.

So, having your open source project on central is a really good idea. It lets your users get at it easily and automatically. You really want to do this.

However, getting your projects on to central isn’t simple (see Guide to uploading artifacts to the Central Repository). It boils down to two choices:

• Package up your code using mvn repository:bundle-create and file a Jira issue for it. This can take four weeks or more.
• Set up and host an rsyncable repository somewhere. This can be automatically pulled into central.

Both of these options are fairly painful. That’s why for the latest release of jslint4java, I was pleased to see that Sonatype are offering an alternative: oss.sonatype.org. This is much simpler because you can just use the usual maven deployment mechanism (or presumably ivy equivalent). A short while later, oss.sonatype.org will sync up with central.

However, the sonatype guys are (rightly) concerned with the quality of artifacts on central. You have to jump extra hoops to go down this road with your open source projects. The main one that tripped me up was requiring all artifacts be GPG signed, which entailed learning GPG and the maven-gpg-plugin. This took me some time. However, subsequent releasing to central is much easier now I’ve been through all the hoops.

• If you want to get your open source project on central, I’d definitely recommend checking out oss.sonatype.org.
• If you want to contribute to an open source project, offering to help get it on to central could be very useful. You’ll not just be helping that project, you’ll also be helping all users of central. The bigger it gets the more useful it is.