HttpServletResponse

황준하·2023년 8월 26일

Spring

SpringMVC

목록 보기

5/19

HttpServletResponse - 기본 사용법

HttpServletResponse 역할
http 응답 메세지 생성

HTTP 응답코드 지정
헤더생성
바디생성

편의기능 제공
contentType, 쿠키, redirect

package hello.servlet.basic.response;

import ...

@WebServlet(name = "responseHeaderServlet", urlPatterns = "/response-header")
public class ResponseHeaderServlet extends HttpServlet {

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //[status-line]
        response.setStatus(HttpServletResponse.SC_OK);

        //[response-headers]
//        response.setHeader("Content-Type", "text/plain;charset=utf-8");
        response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
        response.setHeader("Pragma", "no-cache");
        response.setHeader("my-header", "hello");

        //[Header 편의 메서드]
//        content(response);
//        cookie(response);
        redirect(response);

        //[message body]
        PrintWriter writer = response.getWriter();
        writer.println("ok");

    }

    private void content(HttpServletResponse response) {
        //Content-Type: text/plain;charset=utf-8
        //Content-Length: 2
        //response.setHeader("Content-Type", "text/plain;charset=utf-8");
        response.setContentType("text/plain");
        response.setCharacterEncoding("utf-8");
        //response.setContentLength(2); //(생략시 자동 생성)
    }

    private void cookie(HttpServletResponse response) {
        //Set-Cookie: myCookie=good; Max-Age=600;
        //response.setHeader("Set-Cookie", "myCookie=good; Max-Age=600");
        Cookie cookie = new Cookie("myCookie", "good");
        cookie.setMaxAge(600); //600초
        response.addCookie(cookie);
    }

    private void redirect(HttpServletResponse response) throws IOException {
        //Status Code 302
        //Location: /basic/hello-form.html

//        response.setStatus(HttpServletResponse.SC_FOUND); //302
//        response.setHeader("Location", "/basic/hello-form.html");
        response.sendRedirect("/basic/hello-form.html");
    }
}

HTTP 응답 데이터 - 단순 텍스트, HTML

HTTP 응답 메시지는 주로 다음 내용을 담아서 전달한다.

단순 텍스트 응답
HTML 응답
HTTP API - MessageBody JSON 응답

HttpServletResponse - HTML 응답

package hello.servlet.basic.response;

import...

@WebServlet(name = "responseHtmlServlet", urlPatterns = "/response-html")
public class ResponseHtmlServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //content-Type: text/html;charset=utf-8
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");

        PrintWriter writer = response.getWriter();
        writer.println("<html>");
        writer.println("<body>");
        writer.println("  <div>안녕?<div>");
        writer.println("<html>");
        writer.println("<body>");
    }
}

HTTP 응답으로 HTML을 반환할 때는 content-type을 text/html로 전환해야 한다.

HTTP 응답 데이터 - API JSON

package hello.servlet.basic.response;

import ...

@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: application/json
        response.setContentType("application/json");
        response.setCharacterEncoding("utf-8");

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

        //{"username":"kim", "age":20}
        String result = objectMapper.writeValueAsString(helloData);
        response.getWriter().write(result);
    }
}

HTTP 응답으로 JSON을 반환할 때는 content-type을 application/json으로 지정해야 한다.

Jackson 라이브러리가 제공하는 objectMapper.wrtieValueAsString()를 사용하면 객체를 JSON문자로 변경할 수 있다.

황준하

이전 포스트

HTTP 요청 데이터

다음 포스트