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Maven Profiles Something you need to know

An issue came up today in our CI environment and I learned something new about maven profiles. Something that everyone who uses maven should know. Perhaps, like your environment, our project uses maven2 to build and we take advantage of multiple profiles (see our example here). A common use for profiles is to define new modules and properties. For example:

<profiles>
 <profile>
  <id>integration-tests</id>
  <modules>
   <module>integration</module>
  </modules>
  <properties>
   <app.port>8080</app.port>
  </properties>
 </profile>
<profiles>

This profile is activated when you run mvn -P integration-tests install. But sometimes you want a profile on all the time. Maven profiles have the ability to be actived by default. To do this just do the following:

<profiles>
 <profile>
  <id>integration-tests</id>
  <activation>
   <activeByDefault>true</activeByDefault>
  </activation>
  <modules>
   <module>integration</module>
  </modules>
  <properties>
   <app.port>8080</app.port>
  </properties>
 </profile>
<profiles>

Then you can just run mvn install and that module and property will already be active.

activeByDefault.....Sometimes
Turns out that perhaps maven should have renamed it to activeByDefaultSometimes. Reading their documentation I learned something important about maven profiles:

"This profile will automatically be active for all builds unless another profile in the same pom is activated using one of the previously described methods. All profiles that are active by default are automatically deactivated when a profile in the pom is activated on the command line or through its activation config."

So in my example, if I have more than one profile defined in my pom and I run that new profile, then my integration-tests profile is deactivated. For example, when I run mvn -P SecondProfile, the module and property defined in the integration-tests profiles are not available to my build. One trick to see which profiles are activated when running maven is to run mvn help:active-profiles.

In general I have never been a huge fan of profiles. They feel clumsy, clutter up the cmd line, and are not well known among your team. As their documentation states, "adding profiles to your build has the potential to break portability for your project". Instead of using Profiles, attach to known phases. For example, see my second example from this previous post. In this example, I use the maven-antrun-plugin to attach to the install phase. Now this will run anytime I run mvn install. No clumsy profile I have to memorize and run. Given that, I am not saying you should avoid Profiles all together. Just use them as a last resort.

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Maven not downloading latest snapshots or releases

Ever had issues with maven not downloading the latest snapshots when you know for a fact new snapshots are available? Or your CI environment just deployed a new release (2.0), but when another Hudson job builds, maven does not download the latest 2.0 release artifact. Want an automated solution so you dont have to manually delete the artifacts from your local repository just so maven will download the latest?

Force maven to download latest snapshots
Our company uses Hudson for our automated CI environments. Our project basically has two jobs. The first job checks out and builds HEAD when modified and deploys SNAPSHOT WARs to our companies maven2 repository (artifactory). The second job, which builds nightly, uses maven to download the SNAPSHOT WARs from artifactory, creates an EAR, deploys it to JBoss, and runs integration tests. By default, maven will check once a day for changes to snapshots, so when our second job was triggered, maven inside hudson was not downloading the latest SNAPSHOT WARs.

The solution was to append the -U in the maven goals (run mvn -help). It stands for update-snapshots and tells maven to update all snapshots no matter what.


Force maven to download latest releases
Our next problem was when we created a branch and started creating release artifacts such as 2.0. Unfortunately the description given by maven for the -U option is incorrect (or at least in v 2.0.9), "Forces a check for updated releases and snapshots on remote repositories". As much as I tried, the -U option wouldnt work in our hudson job to force maven to download the latest non-snapshot releases.

The only current solution I know of is to use the maven-dependency-plugin and its goal purge-local-repository. So in your maven goals at some point execute mvn dependency:purge-local-repository and maven will physically delete your projects artifacts from the local repository (/home/user/.m2/repistory) and its transitive dependencies (I think). I tried setting the actTransitively to false and it didnt work for us so I just removed it. I also set verbose to true so I could see what maven deleted in Hudsons console output.



The pipes are used to separate out different goals to isolate its classpath or properties. That way we can skip tests in one run, and then run them in the next all in the same goals section.

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