HTTP 요청 데이터 - API 메시지 바디 - JSON

이번에는 HTTP API에서 주로 사용하는 JSON 형식으로 데이터를 전달해보자.

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

JSON 형식 파싱 추가
JSON 형식으로 파싱할 수 있게 객체를 하나 생성하자 

 

 

 

hello.servlet.basic.HelloData

 

package hello.servlet.basic;
 
import lombok.Getter;
import lombok.Setter;
 
@Getter @Setter
public class HelloData {
    private String username;
    private  int age;
 
 
    //룸복 라이브러리가 있을경우 @Getter @Setter 적으면 자동으로 만들어짐
/*    public String getUsername() {
        return username;
    }
 
    public void setUsername(String username) {
        this.username = username;
    }
 
    public int getAge() {
        return age;
    }
 
    public void setAge(int age) {
        this.age = age;
    }*/
}
 

 

 

 

package hello.servlet.basic.requset;
 
import com.fasterxml.jackson.databind.ObjectMapper;
import hello.servlet.basic.HelloData;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletInputStream;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.util.StreamUtils;
 
import java.io.IOException;
import java.nio.charset.StandardCharsets;
 
@WebServlet (name = "requestBodyJsonServlet", urlPatterns = "/request-body-json")
public class RequestBodyJsonServlet extends HttpServlet {
 
    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.getUsername() = " + helloData.getUsername());
        System.out.println("helloData.getAge() = " + helloData.getAge());
 
        response.getWriter().write("OK");
    }
}
 

 

 

 

Postman으로 실행해보자.
       POST http://localhost:8080/request-body-json
        content-type: application/json (Body    raw, 가장 오른쪽에서 JSON 선택) 
        message body: {"username": "hello", "age": 20}

출력결과
        messageBody={"username": "hello", "age": 20} 
        data.username=hello
        data.age=20

 

참고
JSON 결과를 파싱해서 사용할 수 있는 자바 객체로 변환하려면 Jackson, Gson 같은 JSON 변환 라이브러리 
를 추가해서 사용해야 한다. 스프링 부트로 Spring MVC를 선택하면 기본으로 Jackson 라이브러리
( ObjectMapper )를 함께 제공한다. 

참고
HTML form 데이터도 메시지 바디를 통해 전송되므로 직접 읽을 수 있다. 하지만 편리한 파리미터 조회 기능 
( request.getParameter(...) )을 이미 제공하기 때문에 파라미터 조회 기능을 사용하면 된다.