What is Spring Boot used for?

Spring Boot is used for rapid development, configuration, and deployment of Spring-based standalone, production-ready applications.

Key features and goals:

• Auto-configuration: Automatically configures the Spring application based on the dependencies added. Reduces boilerplate code.
• Embedded servers: Allows running applications as standalone JAR files with embedded servers (Tomcat, Jetty, or Undertow).
• Starters dependencies: Provides a set of convenient POM projects (in Maven) or Gradle scripts that contain a typical set of dependencies. Simplifies dependency management.
• Production readiness: Includes features for monitoring (Spring Boot Actuator), metrics, external configurations, and security.
• No XML configuration: Minimizes or completely eliminates the use of XML configuration in favor of JavaConfig and annotations.

Example of a starter dependency:

<!-- pom.xml -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Example of a minimal Spring Boot application:

// MainApplication.java
package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication // Combines @Configuration, @EnableAutoConfiguration, and @ComponentScan
public class MainApplication {

    public static void main(String[] args) {
        SpringApplication.run(MainApplication.class, args); // Launches the application
    }
}

Spring Boot significantly simplifies the process of creating and deploying Spring applications, making them more "opinionated" and reducing setup time.