Ivy: Agile Dependency Management Tool

In my opinion Ivy is the best dependency management tool compared to others in the field. Unfortunately, good things don’t always receive enough interest they deserve from developer community. Ivy shares the same destiny in this respect.

I have been using Ivy together with Ant to build Java projects for more than 2 years, and I must express my satifcation with what it provides as a dependency management tool; resolving transitive dependencies, evicting old libraries, sycnhronizing target folders, publishing released artifacts are the ones I use a lot among many other features.

Ivy had joined into Apache Incubation several months ago and it has recently graduated as a sub project of Ant. Until yesterday, I was using version 1.4.1 which was the latest stable release available before its join into incubation, and waiting for a stable release, during which its team had only provided two alpha releases. To confess, I had hesitated to upgrade to one of those alpha releases in case I might loose current stability of my development platform. Last night I gave a quick decision not to wait for a final 2.0.0 release and perform the upgrade immediately. Within one hour, upgrade was over and I found myself enjoying features I seek for a long time! The upgrade consists mainly of renaming some xml elements and changing xml namespace in ant build files. It is actually backward compatible with 1.4.1 release, so you don’t have to change anything if you don’t mind seeing some deprecation messages.

Ivy is usually miscompared against Maven which actually claims to provide more than what Ivy alone tries to achieve, and when compared in terms of dependency management features they are usually not examined very carefully.

For example, in Maven feature comparison page, it is stated that both tools are capable of excluding dependencies from tree, and are able to apply a version globally. Unfortunately, nobody will know in which plates those features are served up until they use any of them! In Maven, when you want to exclude some transitive dependencies from your project’s classpath, you still need to know by which dependency they are introduced into, and enlist them exactly in all of those dependency elements in your pom.xml. There is no patternized way to specify what to exclude in your pom. On the other hand, in Ivy you can easily enlist excluded dependencies without knowing from which dependency it comes. You can even use regular expressions to specify them.

One other silly feature of Maven is that it keeps version suffixes of dependencies when it copies them into the target folder. I still can’t believe it doesn’t provide a fature to stipp off version suffixes of dependencies, but within its poor documentation, I couldn’t have found relevant info so far. Unless you build your project with clean option, you might easily end up with having different versions of same library in your deployment. You can even face with this problem while you still perform your build with clean option, during depoying your project into application server. For example, in Eclipse, Tomcat web container just copies your projects war content into its temporary area, and if you only publish your project without cleaning its temporary area you will end up with the same problem menitoned above. It might be a trivial issue to perform clean operations before building and deploying the project, but as you see, there is an obvious friction here during developing software. Ivy avoids such a problem by simply stripping off version suffixes when copying them into target folder.

Similar problem repeats when you remove a dependency from your list, it should also be removed from target folders, too. Ivy has sync feature for this. It will remove any of unlisted jars from your target folder.

Finally, I want to add for the people who want to use Ivy, but restrain himself because of Ivy repository support around the net, that Ivy is able to utilize existing maven repositories.

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