Always specify a version for Maven2 plugins

For the past several months my team has been suffering a lot of downtime because our local builds fail and our Continuous Integration environment fails for what appears to be no reason. What makes these issues difficult to debug is what might fail on your machine, won't fail on mine ("works on my machine"). We eventually found the cause and that was we were not specifying a version for plugins in our maven2 poms. Pretty dumb, eh?

Wrong way

<plugin>
 <groupid>org.apache.maven.plugins</groupid>
 <artifactid>maven-surefire-plugin</artifactid>
</plugin>

Correct way

<plugin>
 <groupid>org.apache.maven.plugins</groupid>
 <artifactid>maven-surefire-plugin</artifactid>
 <version>2.3</version>
</plugin>

This matters because if you leave out the version, maven2 defaults to SNAPSHOT. So what was happening is my project unknowingly became automatic beta testers for third party plugins.

So the moral of the story is always include a version (preferably a stable release version like 2.3 and not 2.3-SNAPSHOT) when defining your plugins. This will go a long ways in making your build more stable. And better yet, define those plugins in your parent pom using the <pluginManagement> section. This keeps your versions in one place so that when you do upgrade intentionally to a newer version you only have to modify it in one place for your entire project. For example:

<pluginmanagement>
  <plugins>
      <plugin>
            <groupid>org.apache.maven.plugins</groupid>
            <artifactid>maven-surefire-plugin</artifactid>
            <version>2.3</version>
        </plugin>
  <plugins>
</plugins>

Specifically the maven-surefire-plugin and maven-war-plugin have cost us a lot already, so recently I updated all our poms to define a version for all the plugins we were using. And one reason I know it would fail for some, but not others, is some prefer to build in offline mode (-o) always which prevented them from seeing the problems.