HttpServletRequest

●HttpServletRequest 역할

HTTP 요청 메시지를 개발자가 직접 파싱해서 사용해도 되지만, 매우 불편하다.

서블릿은 개발자가 HTTP 요청 메시지를 편리하게 사용할 수 있도록 개발자 대신에 HTTP 요청 메시지를 파싱한다.

그리고 그 결과를 "HttpServletRequest" 객체에 담아서 제공한다.

 

HttpServletRequest를 사용하면 다음과 같은 HTTP 요청 메시지를 편리하게 조회할 수 있다.

HTTP 요청 메시지

POST /save HTTP/1.1
Host: localhost:8080
Content-Type: application/x-www-form-urlencoded
username=kim&age=20

● START LINE

  - HTTP 메소드

  - URL

  - 쿼리 스트링

  - 스키마, 프로토콜

● 헤더

  - 헤더 조회

● 바디

  - from 파라미터 형식 조회

  - message body 데이터 직접 조회

HttpServletRequest 객체는 추가로 여러가지 부가기능도 함께 제공한다.

임시 저장소 기능

● 해당 HTTP 요청이 시작부터 끝날 때 까지 유지되는 임시 저장소 기능

  - 저장 

request.setAttribute(name, value)

  - 조회

request.getAttribute(name)

세션 관리 기능

request.getSession(create: true)

중요

HttpServletRequest, HttpServletResponse를 사용할 때 가장 중요한 점은 이 객체들이 HTTP 요청 메시지, HTTP 응답 메시지를 편리하게 사용하도록 도와주는 객체라는 점이다. 따라서 이 기능에 대해서 깊이있는 이해를 하려면 HTTP 스펙이 제공하는 요청, 응답 메시지 자체를 이해해야 한다.

HttpServletRequest - 기본 사용법

HttpServletRequest를 통해서 HTTP 메시지의 여러가지 정보 조회 방법을 실습해보겠다.

RequestHeaderServlet.java ( start line 정보)

package hello.servlet.basic.request;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

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

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

    // start line 정보
    private void printStartLine(HttpServletRequest request) {
        System.out.println("--- REQUEST-LINE - start ---");

        //GET
        System.out.println("request.getMethod() = " + request.getMethod());
        //HTTP/1.1
        System.out.println("request.getProtocol() = " + request.getProtocol());
        //http
        System.out.println("request.getScheme() = " + request.getScheme());
        // 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());
        //https사용 유무
        System.out.println("request.isSecure() = " + request.isSecure());
        System.out.println("--- REQUEST-LINE - end ---");
        System.out.println();
    }



}

Headers정보를 확인하는 방법은 총 2가지 이다. 그 중 첫번째 방법이 아래 예시이다.

RequestHeaderServlet.java ( Headers 정보)

package hello.servlet.basic.request;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.util.Enumeration;

@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));

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

    // start line 정보
    private void printStartLine(HttpServletRequest request) {
        System.out.println("--- REQUEST-LINE - start ---");

        //GET
        System.out.println("request.getMethod() = " + request.getMethod());
        //HTTP/1.1
        System.out.println("request.getProtocol() = " + request.getProtocol());
        //http
        System.out.println("request.getScheme() = " + request.getScheme());
        // 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());
        //https사용 유무
        System.out.println("request.isSecure() = " + request.isSecure());
        System.out.println("--- REQUEST-LINE - end ---");
        System.out.println();
    }

    //Header 모든 정보
    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);
        }

        System.out.println("--- Headers - end ---");
        System.out.println();
    }

}

두번째 방법

package hello.servlet.basic.request;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.util.Enumeration;

@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));

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

    // start line 정보
    private void printStartLine(HttpServletRequest request) {
        System.out.println("--- REQUEST-LINE - start ---");

        //GET
        System.out.println("request.getMethod() = " + request.getMethod());
        //HTTP/1.1
        System.out.println("request.getProtocol() = " + request.getProtocol());
        //http
        System.out.println("request.getScheme() = " + request.getScheme());
        // 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());
        //https사용 유무
        System.out.println("request.isSecure() = " + request.isSecure());
        System.out.println("--- REQUEST-LINE - end ---");
        System.out.println();
    }

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

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

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


        System.out.println("--- Headers - end ---");
        System.out.println();
    }

}

RequestHeaderServlet.java (Header 편리한 조회)

package hello.servlet.basic.request;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.util.Enumeration;

@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);

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

    // start line 정보
    private void printStartLine(HttpServletRequest request) {
        System.out.println("--- REQUEST-LINE - start ---");

        //GET
        System.out.println("request.getMethod() = " + request.getMethod());
        //HTTP/1.1
        System.out.println("request.getProtocol() = " + request.getProtocol());
        //http
        System.out.println("request.getScheme() = " + request.getScheme());
        // 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());
        //https사용 유무
        System.out.println("request.isSecure() = " + request.isSecure());
        System.out.println("--- REQUEST-LINE - end ---");
        System.out.println();
    }

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

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

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


        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();
    }

}

RequestHeaderServlet.java (기타 정보)

package hello.servlet.basic.request;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.util.Enumeration;

@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);

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

    // start line 정보
    private void printStartLine(HttpServletRequest request) {
        System.out.println("--- REQUEST-LINE - start ---");

        //GET
        System.out.println("request.getMethod() = " + request.getMethod());
        //HTTP/1.1
        System.out.println("request.getProtocol() = " + request.getProtocol());
        //http
        System.out.println("request.getScheme() = " + request.getScheme());
        // 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());
        //https사용 유무
        System.out.println("request.isSecure() = " + request.isSecure());
        System.out.println("--- REQUEST-LINE - end ---");
        System.out.println();
    }

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

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

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


        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();
    }

}