# 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](../maven-basic/README.md).

## Usage

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

```shell
        mvn clean verify sonar:sonar
```

## Description

This project consists of 3 modules.

* [`module1`](module1/pom.xml) and [`module2`](module2/pom.xml) contain "business logic" and related unit tests.

* [`tests`](tests/pom.xml) module contains integration tests which test functionality using both modules.
 `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](pom.xml). 

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).

```xml
<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](https://www.jacoco.org/jacoco/trunk/doc/report-aggregate-mojo.html) 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](tests/pom.xml)

```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 with the `${maven.multiModuleProjectDirectory}` so every module knows where the coverage should be imported from

```xml
<properties>
  <sonar.coverage.jacoco.xmlReportPaths>${maven.multiModuleProjectDirectory}/tests/target/site/jacoco-aggregate/jacoco.xml</sonar.coverage.jacoco.xmlReportPaths>
</properties>
```

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

```shell
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](https://docs.sonarqube.org/latest/analysis/scan/sonarscanner-for-maven/)