I have been using maven coberture plugin before but it has one unimplemented function, aggregate cobertura report from multiple module. This can be solved by sonar and dashboard maven plugin, but Sonar requires that is run on a server, i.e. that you have a continuous integration server, but in some cases you have not got there and still is building your application locally than you can use the maven Dashboard plugin.
The parent pom.xml
The jar module pom.xml