Spring Boot MVC and RESTful API Development: A Complete Guide

By Souvik Nandi | 👁️50

Every Spring Application Required Files :

A Spring application typically consists of the following required files:

  1. Bean Class (Java POJO) : A Plain Old Java Object (POJO) used to represent data.
  2. Configuration Files :These files define the configuration of the Spring application and can be of the following types:
    • XML-Based Configuration
    • Java-Based Configuration
    • Annotation-Based Configuration
  3. Test-based files

Annotations in Spring :

Annotations play a crucial role in Spring as they help in replacing XML-based configurations.

Key Points about Annotations:
  • They replace XML-based configuration.
  • Annotations avoid the need for metadata configuration.
  • Spring and Spring Boot use annotations for the best and easiest configuration.
  • Annotations in Java were introduced in JDK 1.5.
  • Every annotation is an interface and starts with the @ symbol.

Spring Web MVC Module:

Spring Web MVC is a framework used for developing web-based applications and REST APIs using the Model-View-Controller (MVC) pattern. 

Architecture Overview :

Client → Controller → Service → Repository → Database

  1. Client (Frontend) : Sends HTTP requests. Receives responses in JSON format.
  2. Controller Layer : Handles HTTP requests. Returns DTO (Data Transfer Object).
  3. Service Layer : Implements business logic.
  4. Repository Layer : Handles database operations.
  5. Database : Stores and retrieves data.

Annotated Controllers in Spring Boot :

Spring MVC provides an annotation-based programming model.
Key Annotations:
  • @Controller   : Defines a controller class in Spring MVC.
  • @RestController : Shorthand for @Controller + @ResponseBody. Returns JSON/XML responses directly.
  • @RequestMapping : Maps HTTP requests to specific controller methods.
  • @PathVariable : Extracts dynamic URL parameters. (ex: /employees/123)
  • @RequestParam : Extracts query parameters.(ex: /employees?pid=123)

Introduction to RESTful APIs :

Representational State Transfer (REST)

REST APIs are a set of rules and conventions for building and interacting with web services. 

REST API Methods and Annotations

Spring Boot provides various HTTP methods for performing CRUD operations.


Spring Boot REST API Project Structure :

A typical Spring Boot REST API project follows this directory structure:

Every Spring Boot REST API Application Required Files : 

A Spring Boot REST API requires specific files to function properly.
  • Model Class (Java POJO) :  Used for reading and writing data through objects.
  • Entity Class (Java POJO): 
    • Annotated with:
    @Entity
    @Id
    @Table
    @GeneratedValue
  • Repository Class (MyRepo.java) : Annotated with :@Repository.
  • Service Interface (MyService.java) : Contains abstract methods.
  • Service Implementation Class (MyServiceImpl.java) : Annotated with: @Service.
  • Controller Class (MyController.java): Annotated with: @RestController.
  • Configuration Files (application.properties or application.yaml)
    • Contains database connection details like:
    • Port number
    • Database connection settings
    • JPA dialect settings
  • Main Application Class (Application.java) :  Contains the main() method to run the application.

Setting Up a Spring Boot REST API :

To build a REST API, you need the following dependencies in your pom.xml:


spring-boot-starter-web → Enables Spring Boot web features.
spring-boot-starter-data-jpa → Provides JPA support.
mysql-connector-java → MySQL database connectivity.

Building a REST API in Spring Boot :

1. Defining the Entity :



Spring Boot provides validation annotations :


2. Creating the Repository :


3. Implementing Business Logic (Service Layer) :
    

4. Creating a Controller : 


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