Jacoco and Sonar code coverage?
I'm in a slightly different setup than you are, using Ant and Sonar 3.01, but... there was one property that did the trick for me, that seemed to be almost entirely undocumented when I looked. I notice the wiki pages have had updates in the last couple of days, which may have changed the doc situation.
<property name="sonar.core.codeCoveragePlugin" value="jacoco" /><property name="sonar.jacoco.reportPath" value="${test.log.dir}/jacoco.exec"/>Setting sonar.jacoco.reportPath explicitly to the file, not a directory, was what finally worked for me.