Skip to main content

Maven and Legacy Projects

Recently I've been helping a colleague introduce a dependency on a legacy project that hasn't been "Maven-ized". Often the "easy way" to add a legacy dependency is to throw the JAR into our Nexus repository and be done with it. But this legacy project was a little trickier and is my new poster child for why taking the easy way can lead to headaches and frustration.

Your legacy project might have compile-time dependencies you need.
Maybe your legacy project implements an external API, or maybe it uses a library and exposes that usage in its API. "So what", you say? "I'll find it at compile-time for my project and I'll add the dependency." Well, now every project that wants to use your legacy project is going to go through the same discovery and embed the dependency in their POM. The right way is to define this dependency in the pom.xml for your legacy project so all dependent projects retrieve it transitively.

Your legacy project might have run-time dependencies you need.
Similar to the last example, your legacy project might use a library but not expose it's use directly. You won't discover the missing dependency until you try and run your project. Here's where the power of the 'runtime' scope of a transitive dependency becomes obvious.

Your legacy project might include library classes within its JAR.
Now here's a real yuck factor when it comes to dealing with other people's code. Our example legacy project bundled a small subset of its dependencies right in its JAR. It wasn't until after we threw it into Nexus that we discovered this rather severe violation of Maven standards. The best solution, get access to the project's source, mavenize the project properly and release a 'pure' artifact. If you don't have access to the legacy project's source you'll need to strip the extra classes from the artifact and construct a pom that includes the right dependency.

Summary
So here's a really quick summary of why not to half-ass adding legacy projects into your Maven infrastructure:
  • Any transitive dependencies will be missing.
  • With legacy jars that embed the classes they depend on you risk class file collisions
Labels:

Comments

Disgruntled Postman said…
That colleague must have been a real n00b!
November 16, 2009 5:43 PM
Post a Comment

Popular posts from this blog

3D Photo Viewer for Looking Glass

The Looking Glass I created my first Chrome extension, which is now live on the Chrome Web Store ! It's built for the Looking Glass , a holographic display that let's you view three-dimensional objects without glasses. I've also opened the source to the extension on GitHub. The Chrome extension allows you to view Facebook's "3D Photos", a feature they added in 2018 for displaying photos that include a depth map like those from phones with dual cameras, such as Apple's "Portrait Mode". Getting Started To use the extension, connect your Looking Glass to your computer, navigate to Facebook and open the viewer from the extension's popup menu. This will open a browser window on the Looking Glass display's screen in fullscreen mode. Opening the Viewer Once the viewer is open, the extension watches for any 3D Photo files being downloaded, so browse around Facebook looking for 3D Photos.  I recommend some of the Facebook groups de
Post a Comment
Read more

My Journey to Fitness, a 5K, and my first Triathlon

At the finish line My name is Brian and Sunday I became a triathlete. My journey started ten months ago when I decided to get back into shape after 15 years of being obese and out-of-shape with some yo-yo dieting in the middle. What changed? I'll get to that. This weekend I competed in the first ever Rocketman Florida Triathlon which took place on the grounds of Kennedy Space Center at Cape Canaveral. In preparation I lost 50 lbs and 12 inches from my waist. But I'm getting ahead of myself. I'm a huge space buff. As a kid I wanted to become an astronaut. I went to Space Camp in Titusville when I was 10. Before that, I saw my first shuttle launch at 7 while on vacation. It was the final launch of the Challenger. I've written about that experience . I've seen three other launches since then including John Glenn's famous return to space as well as the final launch that ended the U.S. Shuttle Program. The idea of biking on the restricted grounds
Post a Comment
Read more

Simplifying logging with Maven and SLF4J (Part 2)

So in my  previous post  I explained how to simplify your logging with Maven and SLF4J. If you haven't read it yet, please do before reading more.  Since then I've discovered an easier and cleaner way to remove the secondary frameworks from your Maven dependency tree. Here's a revised overview of the steps: Decided which logging framework will be your primary, aka who will actually write to your log file. Define the dependency scope of all the secondary frameworks to be ' provided '. Configure your project to depend on drop-in replacements of each secondary framework from SLF4J. Define secondary frameworks as provided Use the dependencyManagement section for this. Its used when you might have a dependency transitively. Add dependency on SLF4J Add the following to your pom.xml Conclusion So now in only 3 steps you can redirect all your logging to your primary logging framework without changing a line of code!
Post a Comment
Read more