Sonar is deeply coupled with Maven.
Sonar uses Maven plugins for launching metrics tools and it uses the Maven conventions for recording the generated XML files.

It would be great whether Sonar uses Gradle for launching metrics tools and for recording the genrated XML files (In addtion, Gradle makes its possible to use the Maven conventions, and it's easier)

Therefore this issue is not a Gradle issue but a Sonar issue.
I sugget raising a Sonar issue and I suggest closing this Gradle issue.

As Gregory pointed out, there is not a good way yet to integrate Sonar with Gradle. But it is definitely something we would like to offer at one point once Sonar is a little bit more build tool agnostic.

We're working hard to decrease the coupling of Sonar with Maven. I hope the integration with alternate build tools like ant or gradle will be possible with versions 2.3 or 2.4.
What sounds missing in Gradle is one of the code coverage plugin already supported by Sonar (Cobertura, Clover or JaCoCo). Emma is not fully supported because its XML reports have no details for files. Do you know if it's planned ?

We definitely want to add support for coverage tools. Ideally, several would be supported, and you could choose which particular tool you want to use for a build. We could start with cobertura, if that helps Sonar integration.

Any news about this integration?

Sonar 2.6 will allow to develop this gradle bootstrap. It is planned for February.

Thanks for providing this enhancement. I will test it out and will let you guys know.