Creating REST APIs Using Spring Boot

Introduction

Spring Boot simplifies Java-based application development. It is widely used to create RESTful APIs due to its auto-configuration, embedded server, and minimal setup. In this article, you'll learn how to build a simple REST API using Spring Boot.

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☑️ What is a REST API?

REST (Representational State Transfer) is an architectural style for designing web services. REST APIs use HTTP methods to perform CRUD operations:

• GET – Read data

• POST – Create new data

• PUT – Update existing data

• DELETE – Remove data

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🛠️ Setting Up Spring Boot Project

1. Using Spring Initializr

Go to https://start.spring.io and select:

• Project: Maven

• Language: Java

• Spring Boot: Latest stable

• Dependencies: Spring Web, Spring Boot DevTools, Spring Data JPA, H2 Database (or MySQL)

Generate the project and unzip it.

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📁 Project Structure

src/
 └── main/
      ├── java/
      │    └── com.example.demo/
      │          ├── controller/
      │          ├── service/
      │          ├── model/
      │          └── repository/
      └── resources/
            └── application.properties

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✍️ Define the Model

// model/Student.java
@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;
    private String email;

    // Getters and Setters
}

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🗃️ Create the Repository

// repository/StudentRepository.java
public interface StudentRepository extends JpaRepository<Student, Long> {
}

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📦 Write the Service Layer

// service/StudentService.java
@Service
public class StudentService {

    @Autowired
    private StudentRepository studentRepository;

    public List<Student> getAllStudents() {
        return studentRepository.findAll();
    }

    public Student getStudent(Long id) {
        return studentRepository.findById(id).orElse(null);
    }

    public Student createStudent(Student student) {
        return studentRepository.save(student);
    }

    public void deleteStudent(Long id) {
        studentRepository.deleteById(id);
    }

    public Student updateStudent(Long id, Student student) {
        student.setId(id);
        return studentRepository.save(student);
    }
}

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🌐 Build the REST Controller

// controller/StudentController.java
@RestController
@RequestMapping("/api/students")
public class StudentController {

    @Autowired
    private StudentService studentService;

    @GetMapping
    public List<Student> getAllStudents() {
        return studentService.getAllStudents();
    }

    @GetMapping("/{id}")
    public Student getStudent(@PathVariable Long id) {
        return studentService.getStudent(id);
    }

    @PostMapping
    public Student createStudent(@RequestBody Student student) {
        return studentService.createStudent(student);
    }

    @PutMapping("/{id}")
    public Student updateStudent(@PathVariable Long id, @RequestBody Student student) {
        return studentService.updateStudent(id, student);
    }

    @DeleteMapping("/{id}")
    public void deleteStudent(@PathVariable Long id) {
        studentService.deleteStudent(id);
    }
}

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⚙️ Configure Application Properties

# application.properties
spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true

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▶️ Run the Application

Run the main class:

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

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🧪 Testing the API

Use Postman, cURL, or any REST client:

• GET /api/students → List all students

• POST /api/students → Add a student

• GET /api/students/{id} → Get a student

• PUT /api/students/{id} → Update a student

• DELETE /api/students/{id} → Delete a student

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📝 Error Handling (Optional)

Add global exception handling using @ControllerAdvice for a cleaner API.

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(EntityNotFoundException.class)
    public ResponseEntity<String> handleNotFound(EntityNotFoundException ex) {
        return new ResponseEntity<>(ex.getMessage(), HttpStatus.NOT_FOUND);
    }
}

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🚀 Deploying Spring Boot APIs

You can deploy to:

• Heroku

• AWS (Elastic Beanstalk or EC2)

• Docker + Cloud Platforms

Package your app using:

mvn clean install
java -jar target/demo-0.0.1-SNAPSHOT.jar

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✅ Conclusion

Spring Boot makes it easy to create RESTful APIs in Java. With minimal configuration and a clean structure, you can build scalable backend services for your web or mobile applications.

Whether you're creating a student app or an enterprise service, Spring Boot is a reliable framework to get your APIs up and running quickly. 

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