REST API Using Spring Boot: Create, Read, Update, Delete (Step-by-Step)

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;    private String name;
    private String email;    // Getters and Setters
}

@RestController
@RequestMapping("/students")
public class StudentController {

    @Autowired
    private StudentRepository repository;

    // CREATE

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

    // READ ALL

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

    // READ BY ID

    @GetMapping("/{id}")
    public ResponseEntity<Student> getStudentById(@PathVariable Long id) {
        return repository.findById(id)
            .map(student -> ResponseEntity.ok(student))
            .orElse(ResponseEntity.notFound().build());
    }

    // UPDATE

    @PutMapping("/{id}")
    public ResponseEntity<Student> updateStudent(@PathVariable Long id, @RequestBody Student updatedStudent) {
        return repository.findById(id)
            .map(student -> {
                student.setName(updatedStudent.getName());
                student.setEmail(updatedStudent.getEmail());
                return ResponseEntity.ok(repository.save(student));
            }).orElse(ResponseEntity.notFound().build());
    }

    // DELETE

    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteStudent(@PathVariable Long id) {
        if (!repository.existsById(id)) {
            return ResponseEntity.notFound().build();
        }
        repository.deleteById(id);
        return ResponseEntity.noContent().build();
    }
}