Master Spring Boot: 35 Essential Q&A for Java Backend Development

Spring vs Spring MVC vs Spring Boot

Spring’s core feature is dependency injection (DI) and inversion of control (IoC), enabling loosely coupled code and easy unit testing. Spring MVC adds a web‑layer with DispatcherServlet, ModelAndView and ViewResolver to simplify web development. Spring Boot eliminates the need for extensive configuration by providing auto‑configuration and starter dependencies, allowing rapid creation of production‑ready applications.

Auto‑configuration

Spring Boot scans the classpath for available frameworks and automatically configures beans, reducing boilerplate configuration. When a MVC JAR is present, Spring Boot can auto‑configure relevant beans.

Spring Boot Starters

Starters are dependency descriptors that bundle commonly used libraries. For example, spring-boot-starter-web includes Spring MVC, Jackson, an embedded Tomcat server, and logging. Other starters cover web services, testing, JDBC, HATEOAS, security, JPA, and REST.

Embedded Server

Spring Boot packages an embedded servlet container (Tomcat, Jetty, or Undertow) inside the executable JAR, so the application runs like a standard Java program without external server installation.

Project Creation

The easiest way to start a Spring Boot project is via Spring Initializr (start.spring.io), where you select group, artifact, dependencies (e.g., Web, Actuator, DevTools) and generate a Maven project. Alternatively, you can create a Maven project manually and add the required starter dependencies.

Maven Plugin

The spring-boot-maven-plugin provides commands such as spring-boot:run to run the app, spring-boot:repackage to create an executable JAR/WAR, and lifecycle management commands ( start, stop).

Live Reload

Adding spring-boot-devtools as a dependency enables automatic restart of the application on classpath changes.

Static Resources

Place static files (e.g., JavaScript, CSS) under src/main/resources/static to serve them directly.

Spring Data and Spring Data REST

Spring Data provides a consistent programming model for data access across relational and NoSQL stores. Spring Data REST can expose repository entities as HATEOAS‑compliant REST endpoints with minimal code, though it is recommended mainly for rapid prototyping.

RequestMapping vs GetMapping

@RequestMapping

can handle multiple HTTP methods, while @GetMapping is a shortcut for handling only GET requests, improving readability.

Configuration Profiles

Spring Boot supports multiple configuration files (e.g., application-dev.properties, application-prod.properties). Activate a profile via the spring.profiles.active property or a JVM argument to load environment‑specific settings.

Database Configuration

For an in‑memory H2 database, include spring-boot-starter-data-jpa, spring-boot-starter-web, and h2 dependencies. To switch to an external database like MySQL, add the MySQL driver, remove H2, and configure spring.datasource.url, username, and password in application.properties.

Custom Configuration

Use @ConfigurationProperties or @Value to bind custom properties defined in application.properties to Java beans.