CS/Spring

HttpServletResponse

leah-only 2025. 5. 2. 14:14

HttpServletResponse 역할

  • HTTP 응답 메시지 생성
    • HTTP 응답 코드 지정
    • 헤더 생성
    • 바디 생성
  • 편의 기능 제공
    • Content-Type
    • Cookie
    • Redirect

Header 관련

1. 헤더 정보

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

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

        //응답 코드 setting
        //[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");

        PrintWriter writer = response.getWriter();
        writer.print("ok");  // 단순 text 응답
    }
}

 

2. 헤더 편의 메서드

public void content(HttpServletResponse response) {
        response.setContentType("text/plain");
        response.setCharacterEncoding("utf-8");
//        response.setContentLength(2); //(생략시 자동 생성)        
    }

    public 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);
    }

 

3. Redirect 편의 메서드

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

        response.sendRedirect("/basic/hello-form.html");
    }

HTTP 응답 데이터

1. HTML 응답

@WebServlet(name = "responseHtmlServlet", urlPatterns = "/response-html")
public class ResponseHtmlServlet extends HttpServlet {

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

        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("</body>");
        writer.println("</html>");
    }
}

 

2. API JSON 응답

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

    //json library
    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("uft-8");

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

참고 : https://www.inflearn.com/course/%EC%8A%A4%ED%94%84%EB%A7%81-mvc-1/dashboard