Jacoco exclude boilerplate layers

jacoco-exclude-boilerplate-layers

When to use

Your JaCoCo / SonarQube coverage number is being dragged down (or artificially inflated) by classes that have no meaningful branches to test: generated Avro stubs, Spring @Configuration, request/response DTOs, JPA/Mongo entities, Kafka listener shells, and dev-only controllers (*Dev.java). Excluding them makes the coverage metric track business logic only.

Steps

1. Identify boilerplate packages in your project

Common patterns:

• **/avro/** — generated schema classes
• **/config/** — Spring configuration
• **/constants/** — static string holders
• **/dto/** — request/response records
• **/entity/** — persistence models
• **/kafka/** — listener plumbing (exclude if logic lives in a service, not the listener)
• **/monitor/** — metrics/actuator hooks
• **/*Dev.java — dev-profile-only endpoints
• **/Application.java — main class

Adjust the list to your actual layout.

2. Add to jacocoTestReport in build.gradle

jacocoTestReport {
    dependsOn test
    reports { html.required = true; xml.required = true }
    afterEvaluate {
        classDirectories.setFrom(
            files(classDirectories.files.collect {
                fileTree(dir: it, excludes: [
                    '**/avro/**',
                    '**/config/**',
                    '**/constants/**',
                    '**/dto/**',
                    '**/entity/**',
                    '**/kafka/**',
                    '**/monitor/**',
                    '**/*Dev.java',
                    '**/Application.java'
                ])
            })
        )
    }
    finalizedBy 'jacocoTestCoverageVerification'
}

3. Mirror the list in jacocoTestCoverageVerification

The verification task reads its own excludes — duplicate the list there or hoist to a shared ext.jacocoExcludes variable.

4. Mirror again in SonarQube properties

sonar {
    properties {
        property 'sonar.exclusions', ['**/avro/**', '**/config/**', ...]
        property 'sonar.coverage.exclusions', ['**/avro/**', '**/config/**', ...]
    }
}

Sonar uses two exclusion keys: sonar.exclusions removes files from analysis entirely, sonar.coverage.exclusions keeps them in analysis but not in coverage math. Usually you want both for boilerplate.

5. Verify

./gradlew clean test jacocoTestReport
open build/reports/jacoco/test/html/index.html

Confirm the excluded packages no longer appear. Coverage % should jump if boilerplate dominated the codebase.

Gotchas

• Trailing whitespace in exclusion globs ('**/avro/** ') silently matches nothing on some JaCoCo versions. Trim them.
• **/*Dev.java won't exclude Kotlin files — add **/*Dev.kt if applicable.
• If a "boilerplate" package contains a handwritten mapper with real branches, don't exclude the whole package — exclude by specific class.
• Keep the three lists (JaCoCo report, JaCoCo verification, Sonar) in sync. Drift is the most common defect here.