Spring vs Spring Boot: An In-depth Comparison
If you’ve done any work with Spring in recent years, you’ve likely come across Spring Boot. Both Spring Framework and Spring Boot are widely used in Java applications, but they serve different purposes.
In this post, we’ll unpack the key differences between the two to help you understand when each one is better suited.
What is Spring Framework?
Spring Framework is a popular Java platform that provides comprehensive infrastructure support for developing Java applications. Spring handles the infrastructure so you can focus on your application logic.
The core features of Spring can be categorized into the following main areas:
- Dependency Injection: The IoC (Inversion of Control) container manages Spring components and bean wiring, allowing for loose coupling between components.
- Aspect-Oriented Programming: Spring AOP provides dynamic proxies and bytecode manipulation to support adding behaviors like logging, transactions, security to objects declaratively.
- Database Access: Spring JDBC provides a level of abstraction over JDBC but still allows working with the JDBC API directly if needed.
- ORM Integration: Spring supports integration with ORM frameworks like Hibernate to reduce boilerplate code for database access.
- Web Framework: The Spring MVC framework provides model-view-controller architecture and ready components for building web applications.
- More: Transactions, messaging, integration, testing support etc.
The core value of Spring is to make it easy to build applications from “Plain Old Java Objects” (POJOs) while avoiding the complexity of directly dealing with infrastructure concerns.
However, being a comprehensive framework, Spring does have a steep learning curve. There is significant upfront configuration required to setup the Spring container and integrate the various components and modules. A basic Spring application will need a lot of configuration to wire up beans, aspect-oriented advisors, database connections, etc.
Overview of Spring Boot
Spring Boot provides an easier way to develop Spring applications with minimal upfront configuration. It takes an opinionated, convention-over-configuration approach to wiring up the Spring ecosystem and boilerplate code. The goals of Spring Boot are:
- Make it easy to create production-ready Spring applications with minimum fuss
- Provide sensible defaults and opinionated starters to simplify configuration
- Reduce boilerplate code as much as possible
- Offer automatic configuration for Spring components as well as common third-party libraries
- Provide metrics, health checks, and externalized configuration
With Spring Boot, you can focus on your business logic and building robust applications and services right from the start without worrying about infrastructure concerns. It drastically reduces the amount of manual configuration and wiring needed to setup Spring applications.
For example, Spring Boot can automatically configure and manage an in-memory database, a production-ready embedded web server like Tomcat, setup metrics and health check endpoints etc. This allows getting started with new Spring projects very quickly.
Key Differences Between Spring and Spring Boot
Now that we have an overview of Spring Framework and Spring Boot, let’s unpack some of the key differences between the two:
This is one of the major differences between Spring and Spring Boot.
Spring applications require a lot of configuration. Beans need to be explicitly configured either via XML or via annotations and JavaConfig. There is no auto-configuration support. You have to manually wire up various components like ORM integrations, web controllers, data sources etc.
Spring Boot minimizes and often completely eliminates most of this boilerplate configuration by automatically configuring beans, auto-detecting components in the classpath, and providing opinionated starters.
For example, by having spring-boot-starter-web in the classpath, it will automatically configure the DispatcherServlet, Embedded Tomcat, Jackson for JSON processing etc.
So with Spring, you control the configuration while Spring Boot configures it for you with sensible defaults.
In Spring, you need to configure and deploy your web applications to an external servlet container like Tomcat. This is an extra step compared to Spring Boot.
Spring Boot lets you run your Spring web application on an embedded servlet container like Tomcat, Jetty or Undertow. This allows creating self-contained web applications and services that you can run and test easily without the need for deploying to an external server.
Spring Boot offers a number of opinionated starter dependencies like spring-boot-starter-web, spring-boot-starter-jpa, spring-boot-starter-security etc. These starters contain auto-configuration code and beans required to quickly setup Spring applications.
For example, spring-boot-starter-web will automatically configure Spring MVC, Jackson for JSON, embedded Tomcat etc. This removes a lot of boilerplate configuration you would have had to do manually with Spring.
Spring Boot provides a spring-boot-starter-parent pom that you can extend from your application pom to inherit useful dependency management and default plugin configurations. This helps manage dependency versions cleanly.
With Spring, you don’t get such dependency management support out of the box and have to handle it yourself or use a third-party solution.
Metrics and Monitoring
Spring Boot Actuator provides production-ready features like metrics, monitoring, health checks etc. You get mature monitoring capabilities like metrics for CPU, memory, HTTP requests automatically in your Spring Boot application.
In Spring Framework, you would have to integrate with a library like JMX or something similar to get metrics and monitoring, which is more work.
Ease of Getting Started
It is quite easy to setup a working Spring Boot application within minutes by using one of the starters, annotated main application class, and minimal configuration. This allows getting an opinionated Spring project up very quickly.
Spring Framework has a steeper learning curve given the vast number of components it provides. Wiring them together takes more time and effort.
When Should You Use Spring vs Spring Boot?
Now that we’ve compared the two frameworks, when should you use Spring vs Spring Boot? Here are some general guidelines:
Use Spring Boot:
- For microservices or web applications when you want to get up and running quickly with minimum config.
- If you need opinionated setup with conventions for a Spring application.
- For standalone and production-ready applications with embedded servers, metrics etc.
- For prototypes or proofs of concept when you want to build something fast.
Prefer Spring Framework when:
- You need more control and customization over configuration than what Spring Boot offers.
- You have very specific infrastructure requirements that Spring Boot opinionated setup doesn’t meet easily.
- For complex enterprise applications that require fine-grained configuration.
- When building shared libraries and frameworks, not standalone applications.
- If you want to deeply understand inner workings of Spring rather than rely on auto-configuration.
In many real-world projects, you will likely use both Spring Boot and Spring Framework together for different layers. For example, Spring Boot for the web layer along with Spring Framework for the services layer.
Spring Framework provides a comprehensive foundation for Java application development while Spring Boot makes setting up Spring applications a breeze with auto-configuration and rapid project generation.
Spring Boot’s goals are to accelerate development by reducing configuration and make it easy to build production-ready applications. Spring Framework gives you more control over configuration at the cost of longer development time.
So Spring and Spring Boot can work together, with Spring Boot enhancing and building upon Spring Framework’s capabilities. Use Spring Boot for rapidly building opinionated standalone applications and Spring Framework when you need more customization.