Spring Boot version versus Spring Framework version?

Demystifying Spring Boot and Spring Framework Versions

Understand the relationship, dependencies, and versioning strategies of Spring Boot and the underlying Spring Framework to avoid common pitfalls and optimize your application development.

A common point of confusion for developers new to the Spring ecosystem is the distinction and relationship between Spring Boot and Spring Framework versions. While they are closely related, they operate on different release cycles and have distinct versioning schemes. Understanding this relationship is crucial for managing dependencies, upgrading applications, and troubleshooting compatibility issues.

The Core Relationship: Boot Builds on Framework

Spring Boot is an opinionated, convention-over-configuration layer built on top of the Spring Framework. Its primary goal is to simplify the development of production-ready Spring applications by providing sensible defaults, embedded servers, and starter dependencies. This means that every Spring Boot application inherently uses a specific version of the Spring Framework.

Spring Boot's layered architecture over Spring Framework

Spring Boot doesn't replace the Spring Framework; it enhances it. When you include spring-boot-starter-web in your project, for example, it pulls in not only Spring Boot's web-related auto-configurations but also the necessary Spring Framework modules like spring-web and spring-webmvc at compatible versions.

Versioning Strategy and Dependencies

Spring Boot and Spring Framework maintain independent release trains. However, each Spring Boot release is designed to work with a specific range, and often a specific major/minor version, of the Spring Framework. This compatibility is managed through Spring Boot's Bill of Materials (BOM) and its starter dependencies.

When you specify a Spring Boot version in your pom.xml (for Maven) or build.gradle (for Gradle), you are implicitly declaring the compatible Spring Framework version. Spring Boot's parent POM or Gradle plugin manages all transitive dependencies, ensuring that all Spring-related modules are aligned.

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.2.5</version>
    <relativePath/>
</parent>

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

Maven configuration specifying Spring Boot parent POM

plugins {
    id 'org.springframework.boot' version '3.2.5'
    id 'io.spring.dependency-management' version '1.1.4'
    id 'java'
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
}

Gradle configuration specifying Spring Boot plugin

Overriding Default Spring Framework Versions (Use with Caution)

While Spring Boot provides a stable set of dependencies, there might be rare cases where you need to use a different Spring Framework version than the one bundled by default. This is generally discouraged unless absolutely necessary, as it can lead to unexpected compatibility issues.

If you must override, you can explicitly declare the spring.framework.version property in your build tool. However, proceed with extreme caution and thorough testing.

<properties>
    <spring.framework.version>6.1.8</spring.framework.version>
</properties>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.2.5</version>
    <relativePath/>
</parent>

Overriding Spring Framework version in Maven (example)

Key Takeaways and Best Practices

Understanding the interplay between Spring Boot and Spring Framework versions is essential for robust application development. Here are some best practices:

1. Step 1

Always rely on Spring Boot's starter-parent or plugin to manage dependencies. This ensures a consistent and compatible set of Spring-related libraries.

2. Step 2

Check the official Spring Boot release notes or documentation for the exact Spring Framework version supported by your chosen Spring Boot version.

3. Step 3

When upgrading, upgrade Spring Boot first. It will automatically bring in the compatible Spring Framework version. Address any breaking changes introduced by the new Spring Boot or Framework versions.

4. Step 4

Avoid manually overriding Spring Framework versions unless you have a critical, well-justified reason and have thoroughly tested the compatibility.

5. Step 5

Be aware of the Java version compatibility. Newer Spring Boot and Spring Framework versions often require newer Java LTS versions (e.g., Spring Boot 3.x requires Java 17+).