[에러해결] HttpMediaTypeNotAcceptableException: Could not find acceptable representation

발생

서비스 계층과 API 계층 연동 복습을 진행하며 계층 분리를 위해 mapstruct를 이용해 mapper를 구현하고, mapper에 필요한 Dto 클래스들을 구현하여 포스트맨으로 테스트를 진행했는데 다음과 같은 에러를 만났다.

Resolved [org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation]

Controller 클래스의 일부 코드(Post 요청에서 에러가 발생하여 Post 메서드 관련)

import com.example.spring.coffee.dto.CoffeePatchDto;
import com.example.spring.coffee.dto.CoffeePostDto;
import com.example.spring.coffee.dto.CoffeeResponseDto;
import com.example.spring.coffee.entity.Coffee;
import com.example.spring.coffee.mapper.CoffeeMapper;
import com.example.spring.coffee.service.CoffeeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;

import javax.validation.Valid;
import javax.validation.constraints.Positive;
import java.util.List;
import java.util.stream.Collectors;

@RestController
@RequestMapping("/coffees")
@Validated
public class CoffeeController {
    CoffeeService coffeeService;
    CoffeeMapper mapper;

    @Autowired
    public CoffeeController(CoffeeService coffeeService, CoffeeMapper mapper) {
        this.coffeeService = coffeeService;
        this.mapper = mapper;
    }

    @PostMapping
    public ResponseEntity postCoffee(@Valid @RequestBody CoffeePostDto coffeePostDto) {
        Coffee coffee = mapper.coffeePostDtoToCoffee(coffeePostDto);
        Coffee response = coffeeService.createCoffee(coffee);

        return new ResponseEntity(mapper.coffeeToCoffeeResponseDto(response), HttpStatus.CREATED);
    }

Mapper 클래스

import com.example.spring.coffee.dto.CoffeePatchDto;
import com.example.spring.coffee.dto.CoffeePostDto;
import com.example.spring.coffee.dto.CoffeeResponseDto;
import com.example.spring.coffee.entity.Coffee;
import org.mapstruct.Mapper;

@Mapper(componentModel = "spring")
public interface CoffeeMapper {

    public Coffee coffeePostDtoToCoffee(CoffeePostDto coffeePostDto);

    public Coffee coffeePatchDtoToCoffee(CoffeePatchDto coffeePatchDto);

    public CoffeeResponseDto coffeeToCoffeeResponseDto(Coffee coffee);
}

mapstruct를 이용한 mapper 구현 코드 (postCoffee() 메서드 관련 코드)

@Component
public class CoffeeMapperImpl implements CoffeeMapper {
    public CoffeeMapperImpl() {
    }

    public Coffee coffeePostDtoToCoffee(CoffeePostDto coffeePostDto) {
        if (coffeePostDto == null) {
            return null;
        } else {
            String korName = null;
            String engName = null;
            int price = false;
            korName = coffeePostDto.getKorName();
            engName = coffeePostDto.getEngName();
            int price = coffeePostDto.getPrice();
            Coffee coffee = new Coffee(korName, engName, price);
            return coffee;
        }
    }
    public CoffeeResponseDto coffeeToCoffeeResponseDto(Coffee coffee) {
        if (coffee == null) {
            return null;
        } else {
            CoffeeResponseDto coffeeResponseDto = new CoffeeResponseDto();
            return coffeeResponseDto;
        }
    }
}

CoffeePatchDto 클래스

import com.example.spring.validator.NotSpace;
import lombok.Getter;
import lombok.Setter;
import org.hibernate.validator.constraints.Range;

import javax.validation.constraints.Pattern;

@Getter
@Setter
public class CoffeePatchDto {

    private long coffeeId;
    @NotSpace
    private String korName;
    @Pattern(regexp = "^([a-zA-Z]+\\s?[a-zA-Z])+$")
    private String engName;
//    @Max(value = 50000)
//    @Min(value = 100)
    @Range(min = 100, max = 50000)
    private int price;
}

CoffeeResponseDto 클래스

public class CoffeeResponseDto {

    private long coffeeId;
    private String korName;
    private String engName;
    private int price;

}

원인

HttpMediaTypeNotAcceptableException 예외는 클라이언트가 요청한 것과 실제로 생성할 수 있는 것이 다를 경우 발생한다고 한다.

즉, 핸들러 메소드가 클라이언트가 요청한 Type으로 응답으로 내려줄 수 없는 것이 원인이였다.

바로 mapper를 구현한 클래스를 먼저 확인했다.(변환 과정에서 문제가 있나 생각이 들어서..)

coffeeToCoffeeResponseDto 메소드의 코드가 변환을 아예 못하고 있었고, CoffeeResponseDto 클래스를 확인하니 Getter가 없는 것을 확인할 수 있었다.

해결

에러 해결을 위해 @Getter과 @AllArgsConstructor 애너테이션을 추가하여 해결하였다. 

import lombok.AllArgsConstructor;
import lombok.Getter;

@Getter
@AllArgsConstructor
@NoArgsConstructor
public class CoffeeResponseDto {

    private long coffeeId;
    private String korName;
    private String engName;
    private int price;
}

Reference

https://stackoverflow.com/questions/28466207/could-not-find-acceptable-representation-using-spring-boot-starter-web

"Could not find acceptable representation" using spring-boot-starter-web

https://memo-the-day.tistory.com/199

Spring MVC의 HttpMediaTypeNotAcceptableException