Multi-module Apache Maven example

This project imports JaCoCo's aggregate XML report to be able to report coverage across modules as well as unit test coverage inside the module. For a basic example see basic maven project.

Usage

• Build the project, execute all the tests and analyze the project with SonarQube Scanner for Maven:

    mvn clean verify sonar:sonar
  

Description

This project consists of 3 modules. module1 and module2 contain "business logic" and related unit tests. The tests module contains integration tests which test functionality using both modules. The tests module is also the one which creates the aggregate coverage report imported into SonarQube.

To generate the report we configure the JaCoCo plugin to attach its agent to the JVM which is executing the tests in the top level pom. This configuration is done in the <pluginManagment> section, so it will be applied on every submodule. It is also configured inside the coverage profile, so this can be activated as needed (e.g. only in CI pipeline).

<build>
  <pluginManagement>
    <plugins>
      <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <executions>
          <execution>
            <goals>
              <goal>prepare-agent</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </pluginManagement>
</build>

Once we have configured JaCoCo to collect coverage data, we need to generate the XML coverage report to be imported into SonarQube. We will use report-aggregate goal which collects data from all modules dependent on the tests module. To achieve this we configure the JaCoCo plugin by configuring execution of report-aggregate goal in verify phase. See pom.xml

<build>
  <plugins>
    <plugin>
      <groupId>org.jacoco</groupId>
      <artifactId>jacoco-maven-plugin</artifactId>
      <executions>
        <execution>
          <id>report</id>
          <goals>
            <goal>report-aggregate</goal>
          </goals>
          <phase>verify</phase>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

This will create a report in tests/target/site/jacoco-aggregate/jacoco.xml. To import this report we will set sonar.coverage.jacoco.xmlReportPaths property in every module on which this coverage should be imported

<properties>
  <sonar.coverage.jacoco.xmlReportPaths>${project.basedir}/../${aggregate.report.dir}</sonar.coverage.jacoco.xmlReportPaths>
</properties>

We use ${aggregate.report.dir} which is defined in the top level pom.xml to avoid duplicating the location of the report in every module.

Alternately we can set this property on the command line with the -D switch:

mvn -Dsonar.coverage.jacoco.xmlReportPaths=C:\projects\sonar-scanning-examples\sonarscanner-maven-aggregate\tests\target\site\jacoco-aggregate\jacoco.xml clean verify sonar:sonar 

We have to use an absolute path, because the report will be imported for each module separately and the path is resolved relative to the module dir.

Documentation

SonarScanner for Maven