# Starters and the Project Layout — Spring Boot

Source: https://www.skillbyai.com/en/spring-boot/i-starters

> Dependencies by capability.

## Pick capabilities, not libraries

A **starter** is a dependency that pulls in a tested set of libraries for one capability: web MVC with an embedded Tomcat, validation, JPA with Hibernate, Actuator, security. The **starter parent** (or Spring Boot's dependency management) pins compatible versions for hundreds of libraries, so you usually omit versions. In Spring Boot 4 the web starter for servlet apps is `spring-boot-starter-webmvc`, and each starter has a matching test starter. Code lives under a base package with the `@SpringBootApplication` class at its root, so component scanning finds everything below it.

## Starters in the demo's pom.xml

This file is from a demo "shop" service generated by start.spring.io for Spring Boot 4.1.1 and Java 21 (Temurin 21.0.12), built with Maven 3.9.16; the project compiled and its tests passed. Simplified excerpt; versions come from the parent, so starters list none.

```xml
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>4.1.1</version>
</parent>

<dependencies>
    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-webmvc</artifactId></dependency>
    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-validation</artifactId></dependency>
    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency>
    <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency>
    <dependency><groupId>com.h2database</groupId><artifactId>h2</artifactId><scope>runtime</scope></dependency>
    <!-- Boot 4 ships matching test starters, e.g. spring-boot-starter-webmvc-test -->
</dependencies>
```

## Let Boot manage versions

Overriding versions managed by Spring Boot often causes subtle incompatibilities; upgrade Boot instead.

**Quiz:** Why do starters usually omit version numbers?

- [x] The Spring Boot parent manages compatible versions
- [ ] Versions are optional in Maven always
- [ ] Starters have no versions
- [ ] Maven picks random versions

*Answer:* The Spring Boot parent manages compatible versions. Dependency management keeps versions aligned.