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Spring Boot Starters

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Core & Setup

Starters are curated dependency descriptors (e.g. spring-boot-starter-web) that bundle all required libraries for a feature, removing version-conflict headaches.

Overview

Spring Boot Starters are pre-packaged, opinionated dependency groups. Each starter pulls in a coherent set of libraries with compatible versions, managed via the spring-boot-dependencies BOM (Bill of Materials). Instead of adding jackson-databind, tomcat-embed-core, spring-web, spring-webmvc, and hibernate-validator individually, you simply add spring-boot-starter-web and Spring Boot handles transitive dependencies and version alignment. You can override any managed version in your own pom.xml/build.gradle.

Common Starters

Starters follow the naming convention spring-boot-starter-{feature}. Third-party integrations use {name}-spring-boot-starter. Each starter activates relevant auto-configuration classes through the classpath condition mechanism.

XML — common Spring Boot starters

<!-- pom.xml — common starters -->
<dependencies>
  <!-- Web: Spring MVC, Tomcat, Jackson, Hibernate Validator -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>

  <!-- JPA: Hibernate, Spring Data JPA, HikariCP -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
  </dependency>

  <!-- Security: Spring Security core + web -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
  </dependency>

  <!-- Actuator: health, metrics, info endpoints -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
  </dependency>

  <!-- Test: JUnit 5, Mockito, AssertJ, MockMvc, Testcontainers -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
  </dependency>
</dependencies>

Switching the Embedded Server

spring-boot-starter-web pulls in Tomcat by default. Exclude it and add the Jetty or Undertow starter to swap the server without changing application code.

XML — swapping embedded server

<!-- Swap Tomcat for Undertow — zero code changes needed -->
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
  <exclusions>
    <exclusion>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-tomcat</artifactId>
    </exclusion>
  </exclusions>
</dependency>

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-undertow</artifactId>
</dependency>

<!-- Reactive web stack — Netty instead of Tomcat -->
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-webflux</artifactId>
  <!-- Pulls in Reactor Netty as the embedded server -->
</dependency>

Overriding Managed Versions

Spring Boot manages library versions via its BOM. Override any version by setting the corresponding Maven property. In Gradle, use ext[] properties or a platform constraint.

XML + Gradle — overriding managed versions

<!-- Override Jackson version (Maven) -->
<properties>
  <jackson.version>2.17.1</jackson.version>
</properties>

<!-- Override in Gradle -->
// build.gradle
ext['jackson.version'] = '2.17.1'

// Or with Gradle version catalog + BOM platform:
dependencies {
    implementation platform("org.springframework.boot:spring-boot-dependencies:${bootVersion}")
    implementation('com.fasterxml.jackson.core:jackson-databind') {
        version { strictly '2.17.1' }
    }
}

// Check what version a starter brings in
./mvnw dependency:tree -Dincludes=com.fasterxml.jackson.core

// Third-party starter example (not from Spring team)
// Convention: {third-party}-spring-boot-starter
implementation 'org.flywaydb:flyway-spring-boot-starter:10.x'
implementation 'io.micrometer:micrometer-registry-prometheus'

Key Points to Remember

1Starters are curated dependency bundles — one starter replaces many individual dependencies.
2spring-boot-dependencies BOM manages all library versions; override via Maven properties.
3Naming convention: spring-boot-starter-{feature} (official) or {name}-spring-boot-starter (third-party).
4Exclude an auto-included transitive dep (e.g. Tomcat) by adding <exclusions> on the starter.
5spring-boot-starter-web = Tomcat; swap to spring-boot-starter-undertow or spring-boot-starter-webflux.
6spring-boot-starter-test brings JUnit 5, Mockito, AssertJ, MockMvc, and Testcontainers.

Interview Questions

What is a Spring Boot starter and why is it useful?

EasyInfosys

How does Spring Boot manage dependency versions without version conflicts?

MediumAmazon

How would you switch from Tomcat to Undertow in Spring Boot?

MediumTCS

What does spring-boot-starter-test include?

EasyWipro

How do you override a dependency version managed by the Spring Boot BOM?

MediumNetflix

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