Creating RESTful web service in SpringBoot

REST api

• REST stands for REpresentational State Transfer. REST is web standards based architecture and uses HTTP Protocol.

• A RESTful web service usually defines a URI, Uniform Resource Identifier a service, provides resource representation such as JSON and set of HTTP Methods.

• @GetMapping,@PostMapping,@PutMapping,DeleteMapping or @RequestMapping(path=“courses”,RequestMethod.Get) : HTTP methods

• @PathVariable: We can use it to dynamically get content from URI. ex -

@GetMapping("/courses/{courseId}") 
public Course getCourse(@PathVariable String courseId){
	// Do stuff with courseId
}

• @RequestBody: When doing post methods, in order to use JSON data in body, we make use of RequestBody. ex -

@PostMapping(path="/courses",consumes="application/json")
	public Course addCourse(@RequestBody Course c) {
		// Do stuff with c
	}

REST api example -

REST endpoints:

• GET /students (Get all students)
• GET /students/{studentsId} (Get specific student)
• POST /students (Add a student)
• PUT /students (Edit a student)
• DELETE /students/{studentId} (Delete specific student)

Student.java

@Entity
public class Course {
	@Id
	private Long id;
	private String name;
	//Getters,Setters & constructors

StudentDao.java

public interface StudentDao extends JpaRepository<Student,Long>{}

StudentService.java : interface

public interface CourseService {
	public List<Student> getAllStudents();
	public Optional<Student> getStudent(long id);
	public Student addStudent(Student s);
	public Student updateStudent(Student s);
	public void deleteStudent(long id);
}

StudentServiceImpl.java

@Service
public class StudentServiceImpl implements StudentService {
	@Autowired
	private StudentDao studentdao;
	
	public StudentServiceImpl() {}

	@Override
	public List<Student> getAllStudents() {	return studentdao.findAll();	}

	@Override
	public Optional<Student> getStudent(long id) {	return studentdao.findById(id);		}
	
	@Override
	public Student addStudent(Student s) {	return studentdao.save(s);	}
	
	@Override
	public Student updateStudent(Student s) {	return studentdao.save(s);	}
	
	@Override
	public void deleteStudent(long id) {	studentdao.deleteById(id);	}
}

StudentController.java

@RestController
public class StudentController {
	@Autowired
	private StudentService studentservice;
	
	@GetMapping("/students")
	public List<Course> getAllStudents(){	return this.studentservice.getAllStudents();	}
	
	@GetMapping("/students/{studentId}")
	public Optional<Course> getStudent(@PathVariable String studentId){ 
		//@PathVariable is used to dynamically get courseId given in URL
		return this.studentservice.getStudent(Long.parseLong(studentId));
	}
	
	@PostMapping(path="/students",consumes="application/json")
	public Course addStudent(@RequestBody Student s) {	return this.studentservice.addStudent(s);	}
	
	@PutMapping("/students")
	public Course updateStudent(@RequestBody Student c) {	return this.studentservice.updateStudent(s);	}
	
	// In this particular function, it is shown how to send HTTP status codes back
	@DeleteMapping("/students/{studentId}")
	public ResponseEntity<HttpStatus> deleteStudent(@PathVariable String studentId) {
		try {
			this.studentservice.deleteStudent(Long.parseLong(studentId));
			return new ResponseEntity<>(HttpStatus.OK);
		} catch(Exception e) {
			return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
		}
	}	
}

application.properties

# can change server port
server.port=8080

# database configs - mysql
spring.datasource.url=jdbc:mysql://localhost:3306/springrest
spring.datasource.username=root
spring.datasource.password=1234
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

# hibernate cofigs
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL57Dialect

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Code Link - Code link

References - Spring Master Class

Article by Arjit Sharma