JaCoCo Multi-Module Spring Coverage Setup

JaCoCo Multi-Module Spring Coverage Setup | Generated by AI

Home 2025.08

Great—JaCoCo works well for a multi-module Spring project. You’ll want:

per-module unit-test coverage;
an aggregate report at the parent;
an optional profile to ingest integration coverage (e.g., Liberty+EAR run hit by Python tests).

Below is a battle-tested setup you can drop in.

Parent `pom.xml` (packaging `pom`)

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.myco.chat</groupId>
  <artifactId>chat-parent</artifactId>
  <version>1.0.0</version>
  <packaging>pom</packaging>

  <modules>
    <module>ChatCommon</module>
    <module>ChatLib</module>
    <module>ChatCore</module>
    <module>ChatWeb</module>
  </modules>

  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.jacoco</groupId>
          <artifactId>jacoco-maven-plugin</artifactId>
          <version>0.8.12</version>
        </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>3.2.5</version>
        </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-failsafe-plugin</artifactId>
          <version>3.2.5</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>

  <!-- Aggregate report for ALL modules' unit tests -->
  <reporting>
    <plugins>
      <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <version>0.8.12</version>
        <reportSets>
          <reportSet>
            <reports>
              <!-- This triggers 'report-aggregate' when you run 'mvn verify' at the parent -->
              <report>report-aggregate</report>
            </reports>
            <configuration>
              <outputDirectory>${project.reporting.outputDirectory}/jacoco-aggregate</outputDirectory>
              <reports>
                <xml>true</xml>
                <html>true</html>
                <csv>false</csv>
              </reports>
              <!-- Optional global filters -->
              <excludes>
                <exclude>**/*Application.class</exclude>
                <exclude>**/*Configuration.class</exclude>
                <exclude>**/generated/**</exclude>
              </excludes>
            </configuration>
          </reportSet>
        </plugins>
      </plugin>
    </plugins>
  </reporting>

  <!-- Profile to add INTEGRATION coverage (e.g., Liberty + Python tests) -->
  <profiles>
    <profile>
      <id>it-coverage</id>
      <activation><activeByDefault>false</activeByDefault></activation>
      <build>
        <plugins>
          <plugin>
            <groupId>org.jacoco</groupId>
            <artifactId>jacoco-maven-plugin</artifactId>
            <version>0.8.12</version>
            <executions>
              <!-- Create an aggregate report that also reads external .exec files -->
              <execution>
                <id>report-aggregate-it</id>
                <phase>verify</phase>
                <goals><goal>report-aggregate</goal></goals>
                <configuration>
                  <!-- Point to one or more .exec files dumped by the Liberty JVM agent -->
                  <dataFiles>
                    <!-- Example paths; adjust for your CI/Liberty location -->
                    <dataFile>${project.basedir}/.jacoco/jacoco-it.exec</dataFile>
                    <!-- You can add more dataFile entries if you dump per-node and want all -->
                  </dataFiles>
                  <outputDirectory>${project.reporting.outputDirectory}/jacoco-aggregate-it</outputDirectory>
                  <reports>
                    <xml>true</xml>
                    <html>true</html>
                    <csv>false</csv>
                  </reports>
                  <excludes>
                    <exclude>**/generated/**</exclude>
                  </excludes>
                </configuration>
              </execution>
            </executions>
          </plugin>
        </plugins>
      </build>
    </profile>
  </profiles>
</project>

Each child module (`ChatCommon/pom.xml`, `ChatLib/pom.xml`, `ChatCore/pom.xml`, `ChatWeb/pom.xml`)

<project>
  <parent>
    <groupId>com.myco.chat</groupId>
    <artifactId>chat-parent</artifactId>
    <version>1.0.0</version>
  </parent>
  <modelVersion>4.0.0</modelVersion>
  <artifactId>ChatCommon</artifactId>
  <packaging>jar</packaging>

  <build>
    <plugins>
      <!-- Attach agent for UNIT tests in this module -->
      <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <version>0.8.12</version>
        <executions>
          <execution>
            <id>prepare-agent</id>
            <goals><goal>prepare-agent</goal></goals>
            <configuration>
              <!-- Put the argLine into a named property, so we can mix with other args -->
              <propertyName>jacocoArgLine</propertyName>
              <append>true</append>
              <excludes>
                <exclude>**/generated/**</exclude>
              </excludes>
            </configuration>
          </execution>
          <execution>
            <id>report</id>
            <phase>verify</phase>
            <goals><goal>report</goal></goals>
            <configuration>
              <reports>
                <xml>true</xml>
                <html>true</html>
                <csv>false</csv>
              </reports>
            </configuration>
          </execution>
          <!-- Optional: enforce minimums -->
          <execution>
            <id>check</id>
            <goals><goal>check</goal></goals>
            <configuration>
              <rules>
                <rule>
                  <element>PACKAGE</element>
                  <limits>
                    <limit>
                      <counter>LINE</counter>
                      <value>COVEREDRATIO</value>
                      <minimum>0.60</minimum>
                    </limit>
                    <limit>
                      <counter>BRANCH</counter>
                      <value>COVEREDRATIO</value>
                      <minimum>0.40</minimum>
                    </limit>
                  </limits>
                </rule>
              </rules>
            </configuration>
          </execution>
        </executions>
      </plugin>

      <!-- Ensure Surefire picks up the agent -->
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <configuration>
          <argLine>${jacocoArgLine} ${surefireArgLine}</argLine>
        </configuration>
      </plugin>

      <!-- (Optional) Failsafe for module-level ITs -->
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-failsafe-plugin</artifactId>
        <configuration>
          <argLine>${jacocoArgLine} ${failsafeArgLine}</argLine>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

Do the same in ChatLib, ChatCore, and ChatWeb. For ChatWeb (a Spring Boot WAR/JAR), the config is identical.

Running it

Unit test coverage across modules (aggregate XML at parent):

mvn -q clean verify
# XML:  target/site/jacoco-aggregate/jacoco.xml
# HTML: target/site/jacoco-aggregate/index.html

Integration coverage from Liberty + Python tests:

Start Liberty with the JaCoCo agent (as discussed earlier), run Python tests, stop or dump. Ensure the .exec lands at ${project.basedir}/.jacoco/jacoco-it.exec (or update that path in the parent profile).
Build aggregate including IT data:

mvn -q -Pit-coverage verify
# XML:  target/site/jacoco-aggregate-it/jacoco.xml
# HTML: target/site/jacoco-aggregate-it/index.html

Notes that save time

Aggregation works only from the parent (packaging pom) with modules declared. Run mvn from the parent directory.
XML (jacoco.xml) is produced when you enable it in <reports>; this is what Codecov/Sonar use.
If you collect multiple .exec files (e.g., several Liberty nodes), either:
- list them all under <dataFiles>…</dataFiles> in the it-coverage profile, or
- merge first (with jacococli.jar merge …) then point to the merged file.
Don’t point classfiles at the EAR; JaCoCo’s report needs the modules’ compiled classes (*/target/classes) and sources—handled automatically by report-aggregate.
If Surefire also sets its own argLine, keep ${jacocoArgLine} first so the agent is not lost.

If you share your exact module package roots and where your Liberty .exec ends up, I can tailor the <dataFiles> and any exclusions so your aggregate XML is clean and CI-ready.

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JaCoCo Multi-Module Spring Coverage Setup | Generated by AI

Parent pom.xml (packaging pom)

Each child module (ChatCommon/pom.xml, ChatLib/pom.xml, ChatCore/pom.xml, ChatWeb/pom.xml)

Running it

Notes that save time

Parent `pom.xml` (packaging `pom`)

Each child module (`ChatCommon/pom.xml`, `ChatLib/pom.xml`, `ChatCore/pom.xml`, `ChatWeb/pom.xml`)