Java Basics: What Is Spring Boot?

Spring Boot is an open source, microservice-based Java web framework. The  Spring Boot framework creates a fully production-ready environment that is completely configurable using its prebuilt code within its codebase. The microservice architecture provides developers with a fully enclosed application, including embedded application servers.

In this blog, we give an overview of Spring Boot, its benefits, and compare it against Spring MVC and Micronaut. Let's get started with a basic overview.

How Popular Is Spring Boot?

How many developers are using Spring Boot in 2024? Find out in the 2024 Java Developer Productivity Report.

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Spring Boot Overview

Spring Boot is just extension of the already existing and expansive Spring frameworks, but it has some specific features that make the application easier for working within the developer ecosystem. That extension includes pre-configurable web starter kits that help facilitate the responsibilities of an application server that are required for other Spring projects.

Spring Boot Benefits

Spring Boot has a number of features that make it a great fit for quickly developing Java applications, including auto-configuration, health checks, and opinionated dependencies.

How Does Spring Boot Work?

Some may be asking yourselves how does Spring Boot have auto configurations and what does that really mean? It really comes down to three simple Spring Boot annotations that provide this feature:

• @SpringBootApplication
• @EnableAutoConfiguration
• @ComponentScan

Between each one of these annotations Spring Boot is able to provide default project dependencies as well as allow for defaults to overwritten.

@SpringBootApplication

@SpringBootApplication is used in the entry point of the application add the class it resides in needs to have to the application main method. The annotation is needed and will provide each of the other two annotations to your Spring Boot application since the @SpringBootApplication includes both inside.

@EnableAutoConfiguration

The @EnableAutoConfiguration does just that it provides each of the representing class with the Automatic Configuration capability.

@ComponentScan

Lastly the @ComponentScan will at initialization scan all the beans and package declarations.

Spring Starter Dependencies

Not only does Spring Boot include annotations but it also uses Spring Starter Dependencies to ensure that your application starts with the correct dependencies and so you can hit the ground running so to speak.

Many times, as an application grows larger it can be hard to properly configure project dependencies, the Spring Boot Starter plugins will help facilitate the dependency management. An example of a spring starter dependencies is the Spring Boot Starter web dependency.

That can be used so that your application can have Rest Endpoints written into your application. Overall, they help streamline the development of these applications so that a team will start from a more complex point so less holes will be presented especially with larger applications.

Is Spring Boot Free?

The short answer is yes -- Spring Boot is free! However, most development teams will dedicate some funds to supporting Spring Boot, or migrate to fully-supported services like WebSphere and JBoss.

When to Use Spring Boot 

Spring Boot should be used anytime microservices are involved and you are planning to use Spring as your primary application framework. 

Spring Boot easily promotes the use of Microservice architecture because of it auto configuration, embedded servers and simplified dependency management. Spring Boot helps development teams to create services quickly and efficiently because there is little time spent with initial set up and downloading the appropriate application servers or packages. To coin Pivotal, developers can ‘just run’ the application.

Learn more about Java Microservices

Spring Boot Example

If you really want to get a good understanding and get your hands dirty with an example of a distributed Spring Boot application with many microservices. I would suggest using the Spring-Petclinic-Microservices project.

This project includes an application with 3 microservices, an API gateway, and some supporting services (Config and Discovery Server). This will provide an out of the box Java web application that is ready to deploy and test with no configurations necessary. Not only does this project provide ready deployments from your IDE but will also provide Docker ready deployments with little steps needed to follow.

The above example can really highlight why a team would look to implement something like Spring Boot for their application design. There is little no configuration need to deploy, with no server need and can be deployed quickly and efficiently. Hence, why in our recent Java developer survey we found that about 83% of correspondents used the Spring Boot as a Runtime platform. Spring Boot is just paramount to a development team who wants to spend their time developing rather than constantly configuring and setting up.

Spring Boot vs. Spring MVC

Before getting into the difference between Spring MVC and Spring Boot first let’s talk about what Spring MVC really is and how is it used.

What Is Spring MVC?

Spring MVC is a web-based framework that provides a 3-tier architecture system called the Model-View-Controller. The design of this architecture is to loosely couple each responsibility of the application logic.

The Model component handles the application data, while the View component handles the presentation layer that facilitates the application requests and presents the application response, and the Controller handles the incoming requests, creates proper models, and returns the appropriate request to the View. Spring MVC is and was used to create HTTP oriented web-based applications with lots of different configurations and environments.

What's the Difference Between Spring Boot and Spring MVC?

The major differences between Spring Boot and Spring MVC come down to differences between context and overall scale.

Spring MVC is a specific Spring-based web framework in a traditional sense. That means it requires manual build configurations, specifying dependencies separately, and the use an application server.

Spring Boot, on the other hand, is more like a module of Spring designed to package Spring applications or frameworks with automation and defaults.

So in theory one could have a Spring MVC project packaged as a Spring Boot application. Both can be classified as Spring frameworks however the scale of Spring Boot encompasses many types of Spring frameworks. While, Spring MVC on the other hand specifies the design of the framework.

Spring Boot vs. Micronaut

Micronaut is a JVM-based framework for building lightweight, modular applications. Like Spring Boot, Micronaut was designed to support the microservice architecture allowing development team to design the quickly and easily.

At this point, I would conclude that Spring Boot still has the advantage to Micronaut. That might simply be due to the fact that Spring Boot has been in the market so much longer and that it is a part of the Spring ecosystem. No matter the case if you were to choose either, each would provide benefits in their own right just in my opinion Spring Boot has better ones.

Final Thoughts

By today’s Java development strategies most development teams are either in, about to in or designing to be in a microservice architecture (80% based on our survey). For that fact, and because Spring Boot has well designed major features to support and leverage a microservice architecture, Spring Boot has become such a major part of the enterprise Java ecosystem and is showing no major signs of decline.

Additional Resources

Looking for further reading on Java frameworks, Spring, or curious about how JRebel can help with Spring Boot development? These resources are a great place to start.

• What to Expect in Spring Boot 3
• Best Java Frameworks of 2020
• Spring Annotations Cheat Sheet
• How to Install JRebel for Spring Boot
• How JRebel Can Help Improve Spring Boot Development

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