If you are a Java developer in today's world, you may have considered learning Spring Boot. Or, you might be already writing code in Spring Boot projects without having a proper understanding of how it originated. To fully understand how Spring Boot works, we have to learn how Spring framework works.

Spring framework was initially released in 2002. How are we supposed to learn 21 years' worth of stuff?

Yeah, it can be a daunting task. But if we can understand the key concepts, everything will start to make sense. Let me take you on a journey to explain how Spring Boot originated and its main features.

The Spring Framework

• Period - Early 2000s

• Why - For building enterprise Java applications

• Key Features :

  • Inversion of Control (IoC)

  • Aspect-Oriented Programming (AOP)

  • Data Access and Transaction Management

• Challenges :

  • XML Config Hell - It heavily relied on XML configurations which led to complex setups

  • Boilerplate Code - Developers had to write a lot of boilerplate code to get simple things done

  • Complexity in integrating with other frameworks and technologies

  • Manual Bean(dependency) wiring

  • Managing Bean Lifecycle

The Spring team wanted to streamline the development process and overcome these challenges.

Spring Boot: Slim, Turbocharged sibling of Spring

• Period - 2004

• Why - Built on Spring framework foundations. Designed to simplify the process of building production-ready Spring applications

• Key Features :

  • Less boilerplate code. No XML configs required

  • Comes with sensible default configurations

  • Embedded web servers and built-in monitoring tools

Let me go through the key abstractions in Spring Boot.

Spring Boot Starters

• What - Pre-configured templates with common dependencies and configurations for specific tasks or technologies

• Why - Simplify dependency management. Reduce the need for manual configs

• Examples :

  • spring-boot-starter-web - For web apps (Has Spring MVC, Tomcat etc.)

  • spring-boot-starter-data-jpa - For JPA-based data access (Has Hibernate, Spring Data JPA and a database driver)

  • spring-boot-starter-security - For handling security concerns (Has Spring Security and related security libraries)

  • spring-boot-starter-test - For testing (Has JUnit, Spring Test and related testing-related libraries)

Auto Configuration

• What - Spring Boot automatically scans the classpath to identify libraries and automatically configures them

• Notes :

  • We can use application properties or write a custom config class to override default configurations

  • We can exclude Specific auto-configurations with the exclude attribute.

Embedded Web Server

• What - Spring Boot comes with embedded web servers (Tomcat, Jetty, Undertow)

• Why - To eliminate the need for external server setup and simplify deployment

• We can customize embedded server settings with application properties or a custom config class

Spring Boot Actuator

• What - Spring Boot comes with built-in tools for monitoring and managing applications

• Features :

  • Health Endpoint - Get insights regarding the application's health

  • Metrics Endpoint - Expose various metrics related to performance and usage

  • Info Endpoint - Expose application-specific details

• Notes :

  • We can write custom endpoints to expose application-specific details

  • If we are using Actuator endpoints, we have to secure the endpoints properly.

Conventions over Configurations

• Spring Boot has sensible default configurations that work out of the box.

• Spring Boot has a standard project structure and naming conventions

• Annotations like @Value can help to inject properties directly into components

Packaging and Deployment

• Packaging options are JAR (Java Archive) or WAR (Web Application Archive).

• WAR requires an external servlet container for deployment while JAR does not need anything like that.

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That's all I have for you today. I'm hoping to do an article series on Spring Boot and explain the concepts and design patterns. If you are interested, you can join our small community by following me. See you soon 🙌