HttpServletRequest

request-header

• 아래 코드는 HttpServletRequest를 통해 HTTP 메시지의 start-line, header 정보 조회 방법이다.

@WebServlet(name = "requestHeaderServlet", urlPatterns = "/request-header")
public class RequestHeaderServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        printStartLine(request);
        printHeaders(request);
        printHeaderUtils(request);
        printEtc(request);
    }

    private static void printStartLine(HttpServletRequest request) {
        System.out.println("--- REQUEST-LINE - start ---");
        System.out.println("request.getMethod() = " + request.getMethod()); //GET
        System.out.println("request.getProtocol() = " + request.getProtocol()); //HTTP/1.1
        System.out.println("request.getScheme() = " + request.getScheme()); //http
        // http://localhost:8080/request-header
        System.out.println("request.getRequestURL() = " + request.getRequestURL());
        // /request-header
        System.out.println("request.getRequestURI() = " + request.getRequestURI());
        //username=hi
        System.out.println("request.getQueryString() = " + request.getQueryString());
        System.out.println("request.isSecure() = " + request.isSecure()); //https 사용유무
        System.out.println("--- REQUEST-LINE - end ---");
        System.out.println();
    }

    private void printHeaders(HttpServletRequest request) {
        System.out.println("--- Headers - start ---");

        /*Enumeration<String> headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            System.out.println(headerName + " : " + headerName);
        }*/

        request.getHeaderNames().asIterator()
                .forEachRemaining(headerName -> System.out.println(headerName + " : " + headerName));

//        String host = request.getHeader("host");
        System.out.println("--- Headers- end ---");
        System.out.println();
    }

    //Header 편리한 조회
    private void printHeaderUtils(HttpServletRequest request) {
        System.out.println("--- Header 편의 조회 start ---"); System.out.println("[Host 편의 조회]"); System.out.println("request.getServerName() = " +
                request.getServerName()); //Host 헤더
         System.out.println("request.getServerPort() = " + request.getServerPort()); //Host 헤더
         System.out.println();
        System.out.println("[Accept-Language 편의 조회]");
        request.getLocales().asIterator()
                .forEachRemaining(locale -> System.out.println("locale = " + locale));
        System.out.println("request.getLocale() = " + request.getLocale());
        System.out.println();
        System.out.println("[cookie 편의 조회]"); if (request.getCookies() != null) {
            for (Cookie cookie : request.getCookies()) {
                System.out.println(cookie.getName() + ": " + cookie.getValue());
            } }
        System.out.println();
        System.out.println("[Content 편의 조회]");
        System.out.println("request.getContentType() = " +
                request.getContentType());
        System.out.println("request.getContentLength() = " +
                request.getContentLength());
        System.out.println("request.getCharacterEncoding() = " +
                request.getCharacterEncoding());
        System.out.println("--- Header 편의 조회 end ---");
        System.out.println();
    }

    //기타 정보
    private void printEtc(HttpServletRequest request) {
        System.out.println("--- 기타 조회 start ---");
        System.out.println("[Remote 정보]");
        System.out.println("request.getRemoteHost() = " +
                request.getRemoteHost()); //

        System.out.println("request.getRemoteAddr() = " +
                request.getRemoteAddr()); //
        System.out.println("request.getRemotePort() = " +
                request.getRemotePort()); //
        System.out.println();
        System.out.println("[Local 정보]"); System.out.println("request.getLocalName() = " + request.getLocalName());
        System.out.println("request.getLocalAddr() = " + request.getLocalAddr());
        System.out.println("request.getLocalPort() = " + request.getLocalPort());
        System.out.println("--- 기타 조회 end ---");
        System.out.println();
    }
}

HTTP 요청 데이터

GET - 쿼리 파라미터

• /url?username=jeong&age=20
• 메시지 바디 없이, URL의 쿼리 파라미터에 데이터를 포함해서 전달
• 검색, 필터, 페이징등에서 많이 사용하는 방식

@WebServlet(name = "requestParamServlet", urlPatterns = "/request-param")
public class RequestParamServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("[전체 파라미터 조회] - start");
        request.getParameterNames().asIterator()
                        .forEachRemaining(paramName -> System.out.println(paramName + " = " + request.getParameter(paramName)));
        System.out.println("[전체 파라미터 조회] - end");
        System.out.println();

        System.out.println("[단일 파라미터 조회] - start");
        String username = request.getParameter("username");
        String age = request.getParameter("age");
        System.out.println("username = " + username);
        System.out.println("age = " + age);
        System.out.println("[단일 파라미터 조회] - end");
        System.out.println();

        System.out.println("[이름이 같은 복수 파라미터 조회] - start");
        String[] usernames = request.getParameterValues("username");
        for (String name : usernames) {
            System.out.println("usernames = " + name);
        }
        System.out.println("[이름이 같은 복수 파라미터 조회] - end");

        response.getWriter().write("OK");
    }
}

POST - HTML Form

• content-type : application/x-www-form-urlencoded
• 메시지 바디에 쿼리 파라미터 형식으로 전달 username=jeong&age=20
• 회원가입, 상품 주문, HTML Form 사용

HTTP message body

• HTTP API에서 주로 사용 (JSON, XML, TEXT)
• 데이터 형식은 주로 JSON 사용
• POST, PUT, PATCH

TEXT

@WebServlet(name = "requestBodyStringServlet", urlPatterns = "/request-body-string")
public class RequestBodyStringServlet 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);

        response.getWriter().write("OK");
    }
}

JSON

@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);

		// JSON 파싱 작업
        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");
    }
}