HTTP 요청 데이터 - API 메시지 바디 - JSON

1. HTTP 요청 데이터 - API 메시지 바디 - JSON

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HTTP API에서 주로 사용하는 JSON 형식으로 데이터를 전달해보자.

 

 

 

2. JSON형식 전송

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• POST http://localhost:8080/request-body-json
• content-type: application/json
• message body: {"username": "hello", "age": 20}
• 결과: messageBody = {"username": "hello", "age": 20}

 

 

3. JSON형식 파싱 추가

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• JSON형식으로 파싱할 객체를 생성

@Getter @Setter
public class HelloData {
    
    private String username;
    private int age;

}

 

 

4. JSON 받기.

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@WebServlet(name = "RequestBodyJsonServlet", urlPatterns = "/request-body-json")
public class RequestBodyJsonServlet extends HttpServlet {

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        ServletInputStream inputStream = request.getInputStream();

        String messageBody = StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);

        System.out.println("messageBody = " + messageBody);
    }
}

messageBody = {
    "username": "hello",
    "age": 20
}

 

 

5. json -> 객체

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• JSON 결과를 파싱해서 사용할 수 있는 자바 객체로 변환하려면 Jackson, Gson 같은 라이브러리 필요.
•  스프링 부트로 Spring MVC를 선택하면 기본으로 Jackson 라이브러리( ObjectMapper ) 제공함.
• ObjectMapper를 사용하면 JSON<-->Object 변환 가능

@WebServlet(name = "RequestBodyJsonServlet", urlPatterns = "/request-body-json")
public class RequestBodyJsonServlet extends HttpServlet {

    //json <--> Object
    private ObjectMapper objectMapper = new ObjectMapper();

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        ServletInputStream inputStream = request.getInputStream();

        String messageBody = StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);

        System.out.println("messageBody = " + messageBody);

        HelloData helloData = objectMapper.readValue(messageBody, HelloData.class);
        System.out.println("helloData.username = " + helloData.getUsername());
        System.out.println("helloData.age = " + helloData.getAge());

        response.getWriter().write("ok~");
    }
}

helloData.username = hello
helloData.age = 20

 

6. GitHub : 210908 MessageBody, json

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GitHub - bsh6463/MVC1