Project Structure and Configuration

Spring Boot follows the standard Gradle and Maven directory layout and keeps configuration in one place: application.properties or application.yml. This chapter tours a generated project: its layout, the build file, configuration files and profiles.

Directory layout

A Gradle project generated by Initializr looks like this. A Maven project differs only in having pom.xml instead of build.gradle.kts, mvnw instead of gradlew, and build output in target/ instead of build/.

demo/
├── build.gradle.kts          # build settings and dependencies
├── settings.gradle.kts       # project name
├── gradlew, gradlew.bat      # Gradle wrapper
└── src/
    ├── main/
    │   ├── java/com/example/demo/
    │   │   ├── DemoApplication.java   # entry point
    │   │   └── todo/                  # one package per feature
    │   │       ├── TodoController.java
    │   │       ├── TodoService.java
    │   │       └── TodoRepository.java
    │   └── resources/
    │       ├── application.properties # configuration
    │       ├── static/                # static files (CSS, JS, images)
    │       ├── templates/             # server-side templates
    │       └── db/migration/          # Flyway migrations
    └── test/java/com/example/demo/    # tests

The build file

The build file declares the Spring Boot plugin and your dependencies. The Spring Boot and dependency-management plugins (or spring-boot-starter-parent in Maven) pin library versions that are known to work with your Spring Boot release, so individual dependencies carry no version.

// build.gradle.kts (Initializr fills in the plugin versions)
java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-webmvc")
    implementation("org.springframework.boot:spring-boot-starter-validation")
    developmentOnly("org.springframework.boot:spring-boot-devtools")
    testImplementation("org.springframework.boot:spring-boot-starter-webmvc-test")
    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
}

In the previous generation the web starter was called spring-boot-starter-web and a single spring-boot-starter-test covered testing. The current generation pairs each technology with its own ...-test starter.

The entry point and package rules

Put the class annotated with @SpringBootApplication in your root package. The annotation scans its own package and every subpackage for components, so a class outside com.example.demo is never registered as a bean. Packaging by feature (todo, user) rather than by layer (controller, service) tends to scale better as the codebase grows.