Starters and the parent POM

Key points

• A starter is an empty jar whose only job is to drag in a curated set of dependencies.
• spring-boot-starter-web gives you Spring MVC, Jackson and an embedded Tomcat in one line.
• The parent POM pins versions. You write dependencies without a <version> tag and they stay compatible.
• Validation is not in the web starter. Add spring-boot-starter-validation if you use @Valid.
• Start a project from start.spring.io rather than hand-writing the POM.

Example

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>3.5.0</version>
</parent>

<properties>
  <java.version>21</java.version>
</properties>

<dependencies>
  <!-- MVC + Jackson + embedded Tomcat -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>
  <!-- Bean Validation: needed for @Valid -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
  </dependency>
</dependencies>

One starter, zero version numbers, a stack that is guaranteed to fit together.