Reference

Build Tools — Maven & Gradle (`build/`)

Runnable examples in `build/`.

Maven lifecycle (phases)

validate → compile → test → package → verify → install → deploy

Common commands:

bash
1mvn compile          # compile main sources2mvn test             # run unit tests3mvn package          # build JAR/WAR4mvn install          # install to local ~/.m25mvn dependency:tree  # show dependency tree (conflict debugging)

Key concepts

Concept	Purpose
`groupId`	org namespace (com.mycompany)
`artifactId`	project name (my-service)
`version`	semver (1.2.3)
`scope`	compile, test, provided, runtime
`dependencyManagement`	centralize versions (BOM)
`parent POM`	inherit plugin/config
`multi-module`	monorepo with shared parent

Semantic versioning

MAJOR.MINOR.PATCH — breaking / feature / fix. Pre-release: 1.0.0-SNAPSHOT.

Conflict resolution

mvn dependency:tree -Dverbose shows evicted versions.
Use <dependencyManagement> or BOM to align versions.
Prefer one logging facade (SLF4J) across the tree.

Gradle (in `build/gradle/`)

build.gradle / build.gradle.kts — project build script
settings.gradle — multi-project root
gradle run, gradle test, gradle build
Gradle wrapper (gradlew) pins Gradle version for CI

Examples in this repo

Path	Demonstrates
`build/maven/simple-app`	minimal POM + exec
`build/maven/multi-module/parent`	parent + api + app modules
`build/maven/bom`	Bill of Materials
`build/gradle/simple-app`	Gradle application plugin