[Java Spring MVC] @GetMapping, @PostMapping, @PutMapping, @PatchMapping & @DeleteMapping

package com.example.ec.web;

import com.example.ec.domain.Tour;
import com.example.ec.domain.TourRating;
import com.example.ec.domain.TourRatingPk;
import com.example.ec.repo.TourRatingRepository;
import com.example.ec.repo.TourRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.stream.Collectors;

@RestController
@RequestMapping(path = "/tours/{tourId}/ratings")
public class TourRatingController {
    TourRatingRepository tourRatingRepository;
    TourRepository tourRepository;

    @Autowired
    public TourRatingController(TourRatingRepository tourRatingRepository, TourRepository tourRepository) {
        this.tourRatingRepository = tourRatingRepository;
        this.tourRepository = tourRepository;
    }

    protected TourRatingController() {}

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public void createTourRating(@PathVariable(value = "tourId") int tourId, @RequestBody @Validated RatingDto ratingDto) {
        Tour tour = verifyTour(tourId);
        tourRatingRepository.save(new TourRating( new TourRatingPk(tour, ratingDto.getCustomerId()), ratingDto.getScore(), ratingDto.getComment()));
    }

    @GetMapping
    public List<RatingDto> getAllRatingsForTour(@PathVariable(value = "tourId") int tourId) {
        verifyTour(tourId);
        return tourRatingRepository.findByPkTourId(tourId)
                // stream it
                .stream()
                // map to dto
                .map(RatingDto::new)
                // convert to a list
                .collect(Collectors.toList());
    }

    @GetMapping(path = "/average")
    public Map<String, Double> getAverage(@PathVariable(value = "tourId") int tourId) {
        verifyTour(tourId);
        return Map.of("average", tourRatingRepository.findByPkTourId(tourId).stream()
            .mapToInt(TourRating::getScore).average()
            .orElseThrow(() -> new NoSuchElementException("Tour has no Ratings")));
    }

    /**
     * Update score and comment of a Tour Rating
     *
     * @param tourId tour identifier
     * @param ratingDto rating Data Transfer Object
     * @return The modified Rating DTO.
     */
    @PutMapping
    public RatingDto updateWithPut(@PathVariable(value = "tourId") int tourId, @RequestBody @Validated RatingDto ratingDto) {
        TourRating rating = verifyTourRating(tourId, ratingDto.getCustomerId());
        rating.setScore(ratingDto.getScore());
        rating.setComment(ratingDto.getComment());
        return new RatingDto(tourRatingRepository.save(rating));
    }
    /**
     * Update score or comment of a Tour Rating
     *
     * @param tourId tour identifier
     * @param ratingDto rating Data Transfer Object
     * @return The modified Rating DTO.
     */
    @PatchMapping
    public RatingDto updateWithPatch(@PathVariable(value = "tourId") int tourId, @RequestBody @Validated RatingDto ratingDto) {
        TourRating rating = verifyTourRating(tourId, ratingDto.getCustomerId());
        if (ratingDto.getScore() != null) {
            rating.setScore(ratingDto.getScore());
        }
        if (ratingDto.getComment() != null) {
            rating.setComment(ratingDto.getComment());
        }
        return new RatingDto(tourRatingRepository.save(rating));
    }

    /**
     * Delete a Rating of a tour made by a customer
     *
     * @param tourId tour identifier
     * @param customerId customer identifier
     */
    @DeleteMapping(path = "/{customerId}")
    public void delete(@PathVariable(value = "tourId") int tourId, @PathVariable(value = "customerId") int customerId) {
        TourRating rating = verifyTourRating(tourId, customerId);
        tourRatingRepository.delete(rating);
    }

    /**
     * Verify and return the TourRating for a particular tourId and Customer
     * @param tourId tour identifier
     * @param customerId customer identifier
     * @return the found TourRating
     * @throws NoSuchElementException if no TourRating found
     */
    private TourRating verifyTourRating(int tourId, int customerId) throws NoSuchElementException {
        return tourRatingRepository.findByPkTourIdAndPkCustomerId(tourId, customerId).orElseThrow(() ->
                new NoSuchElementException("Tour-Rating pair for request("
                        + tourId + " for customer" + customerId));
    }

    /**
     * Verify and return the Tour given a tourId.
     *
     * @param tourId tour identifier
     * @return the found Tour
     * @throws NoSuchElementException if no Tour found.
     */
    private Tour verifyTour(int tourId) throws NoSuchElementException {
        return tourRepository.findById(tourId).orElseThrow(() ->
                new NoSuchElementException("Tour does not exist " + tourId));
    }

    /**
     * Exception handler if NoSuchElementException is thrown in this Controller
     *
     * @param ex exception
     * @return Error message String.
     */
    @ResponseStatus(HttpStatus.NOT_FOUND)
    @ExceptionHandler(NoSuchElementException.class)
    public String return400(NoSuchElementException ex) {
        return ex.getMessage();

    }
}

DTO:

package com.example.ec.web;
import com.example.ec.domain.TourRating;
import javax.validation.constraints.Max;
import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
/**
 * Data Transfer Object for Rating a Tour
 * */

public class RatingDto {

    @Min(0)
    @Max(5)
    private Integer score;

    @Size(max = 255)
    private String comment;

    @NotNull
    private Integer customerId;

    /**
     * Construct a RatingDto from a fully instantiated TourRating.
     *
     * @param tourRating Tour Rating Object
     */
    public RatingDto(TourRating tourRating) {
        this(tourRating.getScore(), tourRating.getComment(), tourRating.getPk().getCustomerId());
    }
    /**
     * Constructor to fully initialize the RatingDto
     *
     * @param score score 1-5
     * @param comment comment
     * @param customerId customer identifier
     */
    private RatingDto(Integer score, String comment, Integer customerId) {
        this.score = score;
        this.comment = comment;
        this.customerId = customerId;
    }

    protected RatingDto() {}

    public Integer getScore() {
        return score;
    }

    public void setScore(Integer score) {
        this.score = score;
    }

    public String getComment() {
        return comment;
    }

    public void setComment(String comment) {
        this.comment = comment;
    }

    public Integer getCustomerId() {
        return customerId;
    }

    public void setCustomerId(Integer customerId) {
        this.customerId = customerId;
    }
}