Spring Boot Interview Questions

Spring Boot and the traditional Spring Framework are both part of the Spring ecosystem, but they have different purposes and offer distinct approaches to building applications. Here's a comparison of the two:

Traditional Spring Framework

1. Configuration:

   • Manual Configuration: Requires extensive XML configuration or Java-based configuration using @Configuration and @Bean annotations.
   • Boilerplate Code: Developers need to write a lot of boilerplate code to set up and configure various components, such as data sources, transaction managers, and view resolvers.

2. Setup and Complexity:

   • Complex Setup: Setting up a traditional Spring application involves configuring multiple XML files or Java configuration classes, which can be time-consuming and complex.
   • Component Scanning: Requires manual configuration of component scanning to detect Spring beans in the application context.

3. Dependency Management:

   • Manual Dependency Management: Developers need to manage dependencies manually by specifying them in a pom.xml (Maven) or build.gradle (Gradle) file without any pre-defined starter packs.

4. Project Structure:

   • Flexible Structure: Allows developers to define their project structure, which can lead to inconsistency across projects.

5. Embedded Server:

   • No Embedded Server: Typically requires deploying the application to an external application server (e.g., Tomcat, Jetty).

6. Development Speed:

   • Slower Development: The need for extensive configuration and boilerplate code can slow down the development process.

Spring Boot

1. Configuration:

   • Auto-Configuration: Provides intelligent defaults and automatically configures many aspects of the application based on the dependencies present in the classpath. This significantly reduces the amount of configuration needed.
   • Convention over Configuration: Emphasizes convention over configuration, offering sensible defaults that can be customized if needed.

2. Setup and Complexity:

   • Simplified Setup: Provides a streamlined setup process, often requiring just a single class annotated with @SpringBootApplication to bootstrap the application.
   • Component Scanning: Automatically scans for Spring components, reducing the need for manual configuration.

3. Dependency Management:

   • Starter POMs: Offers starter POMs (project object models) that bundle common dependencies for specific functionalities (e.g., spring-boot-starter-web, spring-boot-starter-data-jpa), simplifying dependency management.
   • Spring Initializr: A web-based tool and API (start.spring.io) that helps generate Spring Boot projects with pre-configured dependencies.

4. Project Structure:

   • Opinionated Structure: Encourages a standard project structure, which promotes consistency and best practices.

5. Embedded Server:

   • Embedded Server: Includes an embedded web server (Tomcat, Jetty, or Undertow) by default, making it easy to run applications as standalone JARs without needing an external server.

6. Development Speed:

   • Rapid Development: Reduces boilerplate code and configuration, allowing developers to focus more on writing business logic. Features like Spring Boot DevTools further enhance the development experience by enabling live reloading and faster feedback loops.

Key Differences

1. Configuration:

   • Spring Framework: Requires manual configuration (XML or Java).
   • Spring Boot: Uses auto-configuration to reduce the need for manual setup.

2. Setup:

   • Spring Framework: Involves complex setup with multiple configuration files.
   • Spring Boot: Simplifies setup with a single entry point and minimal configuration.

3. Embedded Server:

   • Spring Framework: Typically requires an external application server.
   • Spring Boot: Comes with an embedded server for easy deployment.

4. Dependency Management:

   • Spring Framework: Developers manage dependencies manually.
   • Spring Boot: Provides starter POMs for simplified dependency management.

5. Development Speed:

   • Spring Framework: More boilerplate code and manual setup slow down development.
   • Spring Boot: Reduces boilerplate and speeds up development with intelligent defaults and rapid prototyping tools.

6. Project Structure:

   • Spring Framework: Flexible project structure, which can lead to inconsistencies.
   • Spring Boot: Encourages a standard structure for consistency and best practices.

Example: Setting Up a RESTful Web Service

Traditional Spring Framework

• Dependencies (Maven pom.xml):

  <dependencies>
      <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-webmvc</artifactId>
          <version>5.3.9</version>
      </dependency>
      <!-- Other dependencies -->
  </dependencies>

• Configuration (web.xml):

  <web-app>
      <servlet>
          <servlet-name>dispatcher</servlet-name>
          <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
          <load-on-startup>1</load-on-startup>
      </servlet>
      <servlet-mapping>
          <servlet-name>dispatcher</servlet-name>
          <url-pattern>/</url-pattern>
      </servlet-mapping>
  </web-app>

• Java Configuration:

  @Configuration
  @EnableWebMvc
  public class WebConfig implements WebMvcConfigurer {
      // Configuration beans
  }

• Controller:

  @Controller
  public class MyController {
      @RequestMapping("/hello")
      @ResponseBody
      public String hello() {
          return "Hello, World!";
      }
  }

Spring Boot

• Dependencies (pom.xml):

  <dependencies>
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <!-- Other dependencies -->
  </dependencies>

• Application Entry Point:

  @SpringBootApplication
  public class MyApplication {
      public static void main(String[] args) {
          SpringApplication.run(MyApplication.class, args);
      }
  }

• Controller:

  @RestController
  public class MyController {
      @GetMapping("/hello")
      public String hello() {
          return "Hello, Spring Boot!";
      }
  }

Summary

• Spring Boot: Focuses on simplicity, rapid development, and reducing boilerplate with auto-configuration, embedded servers, and starter POMs.
• Traditional Spring Framework: Offers more flexibility but requires more manual configuration and setup.

Spring Boot streamlines the development process, making it easier to get started with Spring and build production-ready applications quickly.