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Spring Boot - REST Example

Last Updated : 05 Sep, 2025
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Modern web applications follow the Client-Server Architecture, where the frontend (client) communicates with the backend (server) using the HTTP protocol. Servers expose services (APIs) that clients can call via HTTP requests. REST (Representational State Transfer) is a set of architectural principles for building these services.

REST uses standard HTTP methods to perform CRUD operations:

  • POST-> Create
  • GET -> Read
  • PUT -> Update
  • DELETE -> Delete

Step-by-Step Guide to Build a RESTful API using SpringBoot

1. Create the Spring Boot project

Using STS (Spring Tool Suite / Eclipse):

  1. File -> New -> Spring Starter Project -> Next.
  2. Enter Name: book-api (Group com.example, Artifact book-api), Java 17, Maven.
  3. Add dependencies: Spring Web, Spring Boot DevTools.
  4. Click Finish.

Step 2: Project Structure

Once the project is created, we will see the following structure

ProjectStructure

pom.xml:

XML 
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>3.4.3</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>book-api</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>book-api</name>
	<description>Demo project for Spring Boot</description>
	<url/>
	<licenses>
		<license/>
	</licenses>
	<developers>
		<developer/>
	</developers>
	<scm>
		<connection/>
		<developerConnection/>
		<tag/>
		<url/>
	</scm>
	<properties>
		<java.version>17</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-devtools</artifactId>
			<scope>runtime</scope>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

Note:

Since we are not using a database in this example, no configuration is needed in application.properties.

Step 3: Create the POJO Class

A POJO class represents the data model. In this case, we’ll create a Book class.

Book.java:

Java 
package com.example.demo.model;

public class Book {
    private int id;
    private String title;
    private String author;

    public Book(int id, String title, String author)
    {
        this.id = id;
        this.title = title;
        this.author = author;
    }
    // Getters and Setters
    public int getId() { return id; }
    public void setId(int id) { this.id = id; }

    public String getTitle() { return title; }
    public void setTitle(String title)
    {
        this.title = title;
    }

    public String getAuthor() { return author; }
    public void setAuthor(String author)
    {
        this.author = author;
    }
}

Step 4: Create the Service Interface and Service Implementation Class

Here, we have created an interface called BookService which contains all the service methods that our application is going to provide to the user. And BookServiceImpl class that implements the BookService interface. 

Java 
package com.example.demo.service;
import com.example.demo.model.Book;

import java.util.List;

public interface BookService {
    List<Book> findAllBooks();
    Book findBookById(int id);
    void deleteAllBooks();
}

Service Implementation Class

Java 
package com.example.demo.service;

import com.example.demo.model.Book;
import org.springframework.stereotype.Service;
import java.util.ArrayList;
import java.util.List;

@Service
public class BookServiceImpl implements BookService {
    private List<Book> books = new ArrayList<>();

    public BookServiceImpl() {
        // Sample data for books
        books.add(new Book(1, "The Great Gatsby", "F. Scott Fitzgerald"));
        books.add(new Book(2, "1984", "George Orwell"));
        books.add(new Book(3, "To Kill a Mockingbird", "Harper Lee"));
    }

    @Override
    public List<Book> findAllBooks() {
        return books;
    }

    @Override
    public Book findBookById(int id) {
        return books.stream().filter(book -> book.getId() == id).findFirst().orElse(null);
    }

    @Override
    public void deleteAllBooks() {
        books.clear();
    }
}

Step 5: Create the REST Controller

The Controller layer exposes the APIs to the client. Create a RestController class to handle HTTP requests.

ExController.java:

Java 
package com.example.demo.controller;

import com.example.demo.model.Book;
import com.example.demo.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api")
public class ExController {
	 @Autowired
	    private BookService bookService;

	    @GetMapping("/")
	    public String home() {
	        return "Welcome to the Book API!";
	    }

	    @GetMapping("/findbyid/{id}")
	    public Book findBookById(@PathVariable int id) {
	        return bookService.findBookById(id);
	    }

	    @GetMapping("/findall")
	    public List<Book> findAllBooks() {
	        return bookService.findAllBooks();
	    }

	    @DeleteMapping("/delete")
	    public String deleteAllBooks() {
	        bookService.deleteAllBooks();
	        return "All books have been deleted.";
	    }
}

Step 6: Run the Application

The main application class, BookApiApplication, is automatically generated by Spring Boot. It contains the main method to run the application.

BookApiApplication.java:

Java 
package com.example.demo;

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

@SpringBootApplication
public class BookApiApplication {

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

Step 7: Test the APIs

API's list

  • http://localhost:8080/->To save the data
  • http://localhost:8080/findbyid/2-> Find Book by id
  • http://localhost:8080/findall-> Find all books
  • http://localhost:8080/delete-> Delete all books

Test the APIs using Postman to verify they work as expected


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