Annotation #1: @RestController

The @RestController annotation transforms a class into a REST controller, allowing it to manage HTTP requests and generate responses, typically in formats like JSON or XML. While powerful, @RestController works best when paired with other annotations, such as @GetMapping.

For instance, the following code snippet demonstrates a simple API endpoint:

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RestController;

@RestController

public class AppointmentAPI {

@GetMapping("/appointments/hello")

public String hello() {

return "hello from AppointmentAPI!";

}

}

Refer to the video linked below for a detailed demonstration of creating and testing this API.

Annotation #2: @RequestMapping

When dealing with multiple endpoints, specifying the complete path for each can be cumbersome. The @RequestMapping annotation allows you to set a base path for all methods in a class, simplifying your endpoint definitions.

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

@RestController

@RequestMapping("/appointments")

public class AppointmentAPI {

@GetMapping("/hello")

public String hello() {

return "hello from AppointmentAPI!";

}

}

Refer to the video linked below for a detailed demonstration of creating and testing this API.

Annotation #3: @GetMapping and #4: @PathVariable

The @GetMapping annotation is commonly used to retrieve data, such as listing or viewing details. Below is an example of how to implement these functionalities:

@GetMapping("/")

public List<AppointmentDTO> list() {

return this.appointments;

}

@GetMapping("/{id}")

public AppointmentDTO view(@PathVariable("id") Long id) {

return this.appointments.stream()

.filter(a -> a.id.equals(id))

.findFirst()

.orElse(null);

}

Refer to the video linked below for a detailed demonstration of creating and testing this API.

Annotation #5: @PostMapping and #6: @RequestBody

The @PostMapping annotation is utilized to handle HTTP POST requests, allowing you to create new entities such as appointments. The @RequestBody annotation enables automatic extraction of data from the request body.

@PostMapping("/")

public void create(@RequestBody AppointmentDTO appointmentDTO) {

appointmentDTO.id = lastId++;

this.appointments.add(appointmentDTO);

}

Refer to the video linked below for a detailed demonstration of creating and testing this API.

Annotation #7: @PutMapping

The @PutMapping annotation is used for updating existing entities. Typically, you will include an ID in the endpoint to identify the entity being updated.

@PutMapping("/{id}")

public void update(@PathVariable("id") Long id, @RequestBody AppointmentDTO appointmentDTO) {

var existingAppointment = this.appointments.stream()

.filter(a -> a.id.equals(id))

.findFirst()

.orElse(null);

if (existingAppointment != null) {

existingAppointment.title = appointmentDTO.title;

existingAppointment.date = appointmentDTO.date;

}

}

Annotation #8: @DeleteMapping

The @DeleteMapping annotation is used to remove an existing entity, such as canceling an appointment. It generally requires only an ID as a path variable.

@DeleteMapping("/{id}")

public void delete(@PathVariable("id") Long id) {

var existingAppointment = this.appointments.stream()

.filter(a -> a.id.equals(id))

.findFirst()

.orElse(null);

if (existingAppointment != null) {

this.appointments.remove(existingAppointment);

}

}

Annotation #9: @RequestParam

Finally, the @RequestParam annotation is valuable for handling search queries within your API.

@GetMapping("/search")

public List<AppointmentDTO> search(@RequestParam("date") String date) {

return this.appointments.stream()

.filter(a -> a.date.equals(LocalDate.parse(date)))

.collect(Collectors.toList());

}