Why does the Maven command "mvn sonar:sonar" work without any plugin configuration in my "pom.xml"?

Question

I have a Maven web project in my repo.

I am a Maven noob but still I understand the fact that there are plugins which we need to configure only then we could run plugin specific commands.

Facts:

I have a sonar server running on my local machine at port 9000.

I have not added any sonar specific plugin in my POM.xml

Reference:

http://www.sonarsource.org/we-had-a-dream-mvn-sonarsonar/

Observation:

But still when I run mvn sonar:sonar in my project from command line it works fine.

Matter of the fact is I have NOT configured sonar plugin in my POM.xml Even then from where the hell Maven is picking up and understanding "sonar:sonar" goal/command?

Question / curiosity:

I don't want the working knowledge of sonar itself. I want to know why mvn sonar:sonar works without configuring a sonar plugin in my pom.xml

WHY and how?

Answer 1

The reason is that the Sonar Maven Plugin is hosted at the Codehaus Mojo project and benefits from the groupId "org.codehaus.mojo". This allows to use the shortcut "sonar:sonar" instead of "org.codehaus.mojo:sonar-maven-plugin::sonar" (see the section "Configuring Maven to Search for Plugins" of the Maven documentation)

Answer 2

Sonar has its own set of plugins (e.g. maven-checkstyle-plugin) which it is running when being invoked. These plugins are automatically configured according to your project settings in your configured Sonar server.

The reasoning behind this to have a controlled configuration in your sonar instance.

The reason it is working automatically for you is that you are using the default values for your sonar server installation (localhost:9000).

This 'zero-configuration' approach is further detailed here: We had a dream : mvn sonar:sonar