[Spring] HttpServletResponse 객체로 JSON 데이터 반환하기 / @ResponseBody 로 JSON 데이터 반환하기

@WebServlet(name = "responseJsonServlet", urlPatterns = "/response-json")
public class ResponseJsonServlet extends HttpServlet {

    private ObjectMapper objectMapper = new ObjectMapper();

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // content -type
        response.setContentType("application/json");
        response.setCharacterEncoding("utf-8");

        HelloData helloData = new HelloData();
        helloData.setUsername("won");
        helloData.setAge(20);

        // JSON 형태로 변환하기
        // {"username" : "won", "age" : 20}
        String result = objectMapper.writeValueAsString(helloData);

        response.getWriter().write(result);
    }
}

 

 

Spring에서 제공하는 Controller를 통해서 코드를 작성해보자.

@RestController
public class RequestBodyJsonController {

    // Jackson 라이브러리인 ObjectMapper 를 생성한다
    private ObjectMapper objectMapper = new ObjectMapper();

    @PostMapping("/response-body-json-v1")
    public HelloData responseBodyJsonV1(HttpServletRequest request, HttpServletResponse response) 
    	throws IOException {
        ServletInputStream inputStream = request.getInputStream();
        String messageBody = StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);
    
        HelloData helloData = objectMapper.readValue(messageBody, HelloData.class);
        return helloData;
    }
    
    @PostMapping("/response-body-json-v2")
    public HelloData responseBodyJsonV2(@RequestBody HelloData helloData) throws IOException {
        // helloData 를 바로 사용할 수 있다.
        return helloData;
    }
}