[Spring Boot] 4. Request 객체

Mar 20, 2025

Contents

Get Post C - V patton (Controller - View)WEB-INF 폴더(보안폴더) 내의 파일 찾기 Redirection M - C - V patton (Model - Controller - View)

Get

‼️

select (get요청) request의 핵심 method 주소에 붙이는 데이터 -> where에 걸린다

➡ localhost:8080/good.do 의 Request Header에 있는 “User-Agent” 와 “Host” 확인해보기

DemoServlet


package org.example.demo6;

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("*.do")
public class DemoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // select (get요청)
        // request의 핵심 method
        // 주소에 붙이는 데이터 -> where에 걸린다
        String method = req.getHeader("User-Agent");
        System.out.println("User-Agent:" + method);
        String Host = req.getHeader("Host");
        System.out.println("Host:" + Host);

    }

✅ 출력 결과

➡ localhost:8080/demo.do?username=ssar&password=1234 를 입력했을 때

path, method, queryString, username, password 가 어떻게 나오는지 확인해보기

DemoServlet


package org.example.demo6;

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;

// localhost:8080/demo.do?username=ssar&password=1234
@WebServlet("*.do")
public class DemoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // select (get요청)
        // request의 핵심 method
        // 주소에 붙이는 데이터 -> where에 걸린다
        String path = req.getRequestURI();
        System.out.println("path: " + path);

        String method = req.getMethod();
        System.out.println("method: " + method);

        String queryString = req.getQueryString();  // 구체적 질의를 하기 위해 필요 = sql where
        System.out.println("queryString: " + queryString);

        String username = req.getParameter("username"); // 키값을 꺼내서 값을 얻을때
        System.out.println("username: " + username);

        String password = req.getParameter("password"); // 키값을 꺼내서 값을 얻을때
        System.out.println("password: " + password);


    }

✅ 출력 결과

➡ Request에 있는 정보 확인해보기

DemoServlet


package org.example.demo6;

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("*.do")
public class DemoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        Enumeration<String> headerNames = req.getHeaderNames();

        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            String headerValue = req.getHeader(headerName);
            System.out.println(headerName + ": " + headerValue);
        }
    }

✅ 출력 결과

⬇Request 에 들어있는 정보


host: localhost:8080
connection: keep-alive
sec-ch-ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"
upgrade-insecure-requests: 1
user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
sec-fetch-site: none
sec-fetch-mode: navigate
sec-fetch-user: ?1
sec-fetch-dest: document
accept-encoding: gzip, deflate, br, zstd
accept-language: ko-KR,ko;q=0.9,en-US;q=0.8,en;q=0.7

Post

DemoServlet


// insert
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String body = "";

        BufferedReader br = req.getReader();

        while (true) {
            String line = br.readLine();
            if (line == null) break;

            body = body + line;
        }
        System.out.println("body: " + body);


    }
}

➡ Postman에서 text로 입력해보기

✅ 출력 결과

⬇ body에 text가 그대로 담긴다

➡ Postman에서 x-www-formurlencoded로 key, value 넣기

username=ssar 과 password=1234 가 &로 결합되어 ‘username=ssar&password=1234’ 로 전송

➡ ‘username=ssar&password=1234’ 라고 들어오면 getParameter()로 파싱이 가능해짐

✅ 출력 결과

DemoServlet


// insert
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

String username = req.getParameter("username");
        String password = req.getParameter("password");
        System.out.println("username: " + username);
        System.out.println("password: " + password);

index.html


<!DOCTYPE html>
<html lang="ko">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <form action="http://localhost:8080/hello.do" method="post" enctype="application/x-www-form-urlencoded">
        <input type="text" placeholder="Enter username" name="username">
        <input type="text" placeholder="Enter password" name="password">
        <button type="submit">전송</button>
    </form>
</body>

</html>

✅ 출력 결과

HomeServlet


package org.example.demo7;

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("/home.jsp")
public class HomeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setHeader("Content-Type", "text/html");
        String name = "홍길동";
        String body = """
                <html>
                <head>
                    <title>Title</title>
                </head>
                <body>
                <h1>Home Page</h1>
                <hr>
                ${name}
                </body>
                </html>
                """.replace("${name}", name);

        resp.getWriter().println(body);
    }
}

home.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>Home Page</h1>
<hr>
<%
    String name = "홍길동";

%>
<%=name%>
</body>
</html>

C - V patton (Controller - View)

FrontController


package org.example.demo8;

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;

// localhost:8080/hello.do?path=a
@WebServlet("*.do")
public class FrontController extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("common logic");
        String path = req.getParameter("path");
        String name = "ssar";
        if (path.equals("a")) {
            req.setAttribute("name", name);
            req.getRequestDispatcher("a.jsp").forward(req, resp);
        } else if (path.equals("b")) {
            req.setAttribute("name", name);
            req.getRequestDispatcher("b.jsp").forward(req, resp);
        } else if (path.equals("c")) {
            req.setAttribute("name", name);
            req.getRequestDispatcher("c.jsp").forward(req, resp);
        } else {

        }
    }
}

a.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>A view</h1>
<%
    String name = (String) request.getAttribute("name");  // object -> String (다운캐스팅)
%>
<h3>값: <%=name%>
</h3>
</body>
</html>

✅ 출력 결과

b.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>B view</h1>
<h3>${name}</h3>
</body>
</html>

✅ 출력 결과

c.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>C view</h1>
<h3>${name}</h3>
</h3>
</body>

✅ 출력 결과

⚠ But, 파일명으로도 찾는 게 가능하다 → Common Logic을 타지 않음

WEB-INF 폴더(보안폴더) 내의 파일 찾기

‼️

파일을 바로 찾는 것은 불가능 → http://localhost:8080/a.jsp (❌)

무조건 단일진입벽(Controller)을 통해 찾는다 → Common Logic 수행

DemoServlet


package org.example.demo9;

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;

// http://localhost:8080/
@WebServlet("/") // '/' 이후의 형태는 모든 요청이 여기로 몰린다 ex) /, /abc, /a, /b, /c ...
public class DemoServlet extends HttpServlet {

    // http://localhost:8080?path=a     /는 생략가능
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // body -> path=값&name=값
        // queryString -> ?path=값&name=값
        String path = req.getParameter("path");

        if (path.equals("a")) {
            req.setAttribute("name", "ssar");
            req.getRequestDispatcher(ViewResolver.viewName("a")).forward(req, resp);
        } else if (path.equals("b")) {
            req.setAttribute("age", 20);
            req.getRequestDispatcher(ViewResolver.viewName("b")).forward(req, resp);
        }
    }
}

ViewResolver


package org.example.demo9;

public class ViewResolver {
    private static final String prefix = "/WEB-INF/views/";
    private static final String suffix = ".jsp";

    public static String viewName(String filename) {
        return prefix + filename + suffix;
    }
}

a.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>a.jsp</h1>
<h3>내 이름은: ${name}</h3>
</body>
</html>

✅ 출력 결과

b.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>b.jsp</h1>
<h3>내 나이는: ${age}</h3>
</body>
</html>

✅ 출력 결과

DispatcherServlet


package org.example.demo10;

import jakarta.servlet.ServletConfig;
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 org.example.demo10.core.ComponentScan;
import org.example.demo10.core.RequestMapping;
import org.example.demo10.core.ViewResolver;

import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Set;

@WebServlet("*.do")
public class DispatcherServlet extends HttpServlet {

    private Set<Object> controllers;

    @Override
    public void init(ServletConfig config) throws ServletException {
        // 1. 컴포넌트 스캔
        ComponentScan componentScan = new ComponentScan(config.getServletContext());
        controllers = componentScan.scanClass("org.example.demo10.controller");
        //System.out.println(controllers.size());
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // localhost:8080/user.do?path=join
        String path = req.getParameter("path");

        // 2. 라우팅
        String templatePath = route(path);

        // 3. 이동
        if (templatePath == null) {
            resp.setStatus(404);
            resp.getWriter().println("<h1>404 Not Found</h1>");
        } else {
            req.getRequestDispatcher(ViewResolver.viewName(templatePath)).forward(req, resp);
        }


    }

    private String route(String path) {
        for (Object instance : controllers) {
            Method[] methods = instance.getClass().getMethods();

            for (Method method : methods) {
                RequestMapping rm = method.getAnnotation(RequestMapping.class);

                if (rm == null) continue; // 다음 for문으로 바로 넘어감

                if (rm.value().equals(path)) {
                    try {
                        return (String) method.invoke(instance);

                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }
                }
            }
        }
        return null;
    }
}

ComponentScan


package org.example.demo10.core;

import jakarta.servlet.ServletContext;

import java.io.File;
import java.util.HashSet;
import java.util.Set;

public class ComponentScan {
    private final ServletContext servletContext;

    public ComponentScan(ServletContext servletContext) {
        this.servletContext = servletContext;
    }

    // 클래스를 스캔하는 메소드
    public Set<Object> scanClass(String pkg) {
        Set<Object> instances = new HashSet<>();
        try {
            // 톰캣의 webapps 폴더 내 WEB-INF/classes 경로 가져오기
            String classPath = servletContext.getRealPath("/WEB-INF/classes/");

            // C:\Program Files\Apache Software Foundation\Tomcat 11.0\webapps\ROOT\WEB-INF\classes\
            File slashDir = new File(classPath);
            File dotToSlashDir = new File(slashDir, pkg.replace(".", File.separator));

            for (File file : dotToSlashDir.listFiles()) {
                //System.out.println(file.getName());

                String className = pkg + "." + file.getName().replace(".class", "");
                //System.out.println(className);

                try {
                    Class cls = Class.forName(className);
                    if (cls.isAnnotationPresent(Controller.class)) {
                        //System.out.println("Controller 어노테이션");
                        Object instance = cls.getDeclaredConstructor().newInstance();
                        instances.add(instance);
                    }
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            }

            return instances;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

}

ViewResolver


package org.example.demo10.core;

public class ViewResolver {
    private static final String prefix = "/WEB-INF/views/";
    private static final String suffix = ".jsp";

    public static String viewName(String filename) {
        return prefix + filename + suffix;
    }
}

UserController


package org.example.demo10.controller;

import org.example.demo10.core.Controller;
import org.example.demo10.core.RequestMapping;

@Controller
public class UserController {

    @RequestMapping("join")
    public String join() {
        System.out.println("UserController join");
        return "join";
    }

    @RequestMapping("login")
    public String login() {
        System.out.println("UserController login");
        return "login";
    }
}

BoardController


package org.example.demo10.controller;

import org.example.demo10.core.Controller;

@Controller
public class BoardController {
}

Annotation / @Controller


package org.example.demo10.core;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface Controller {
}

Annotation / @RequestMapping


package org.example.demo10.core;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface RequestMapping {
    String value();
}

join.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>join page</h1>
</body>
</html>

✅ 출력 결과

login.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>login page</h1>
</body>
</html>

✅ 출력 결과

templatePath == null

➡ path가 ‘join’ 이나 ‘login’ 이 아니면

resp.setStatus(404);
            resp.getWriter().println("<h1>404 Not Found</h1>");

✅ 출력 결과

Redirection

DispatcherServlet


package org.example.demo10;

import jakarta.servlet.ServletConfig;
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 org.example.demo10.core.ComponentScan;
import org.example.demo10.core.RequestMapping;
import org.example.demo10.core.ViewResolver;

import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Set;

@WebServlet("*.do")
public class DispatcherServlet extends HttpServlet {

    private Set<Object> controllers;

    @Override
    public void init(ServletConfig config) throws ServletException {
        // 1. 컴포넌트 스캔
        ComponentScan componentScan = new ComponentScan(config.getServletContext());
        controllers = componentScan.scanClass("org.example.demo10.controller");
        //System.out.println(controllers.size());
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // localhost:8080/user.do?path=join
        String path = req.getParameter("path");

        // 2. 라우팅
        String templatePath = route(path);

        // 3. redirection
        // localhost:8080/user.do?path=login
        if (templatePath.contains("redirect:")) {
            String redirectPath = templatePath.replace("redirect:", "");  // home
//            resp.setStatus(302);
//            resp.setHeader("Location", "?path=" + redirectPath);
            resp.sendRedirect("?path=" + redirectPath);
            return;  // 밑으로 안 내려가게 여기서 종료
        }

        // 4. 이동
        if (templatePath == null) {
            resp.setStatus(404);
            resp.getWriter().println("<h1>404 Not Found</h1>");
        } else {
            req.getRequestDispatcher(ViewResolver.viewName(templatePath)).forward(req, resp);
        }


    }

    private String route(String path) {
        for (Object instance : controllers) {
            Method[] methods = instance.getClass().getMethods();

            for (Method method : methods) {
                RequestMapping rm = method.getAnnotation(RequestMapping.class);

                if (rm == null) continue; // 다음 for문으로 바로 넘어감

                if (rm.value().equals(path)) {
                    try {
                        return (String) method.invoke(instance);

                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }
                }
            }
        }
        return null;
    }
}

home.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>home page</h1>
</body>
</html>

➡ http://localhost:8080/hello.do?path=login 입력하면?

➡ http://localhost:8080/hello.do?path=home 으로 redirect

BoardController


package org.example.hello.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;


@Controller
public class BoardController {

    // localhost:8080/detail
    @GetMapping("/detail")
    public String detail() {
        return "detail";
    }


    // localhost:8080/home
    @GetMapping("/home")
    public String home() {
        return "home";
        
    }

}

UserController


package org.example.hello.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;

@Controller
public class UserController {

    // 줄게 -> 회원가입 정보
    // localhost:8080/join
    // body : username=ssar
    // header : Content-Type : application/x-www-form-urlencoded
    @PostMapping("/join")
    public String join(String username) {
        // 1. DB insert
        System.out.println("username: " + username);
        // 2. 응답
        return "redirect:/home";
    }

    // 줘 -> 회원가입 페이지
    @GetMapping("/join-form")
    public String joinForm() {
        return "join-form";
    }
}

join-form.mustache


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>회원가입 페이지</h1>
<form action="/join" method="post">
    <input type="text" name="username" placeholder="Enter username">
    <button type="sumit">회원가입</button>
</form>
</body>
</html>

⬇ input tag에 ‘ssar’을 입력하면?

⬇ redirection 되서 home 으로 이동

home.mustache


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>홈 페이지</h1>
</body>
</html>

detail.mustache


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>상세보기 페이지</h1>
</body>
</html>

M - C - V patton (Model - Controller - View)

Contents

Get Post C - V patton (Controller - View)WEB-INF 폴더(보안폴더) 내의 파일 찾기 Redirection M - C - V patton (Model - Controller - View)

Spring Boot

[Spring Boot] 4. Request 객체

김미숙

Mar 20, 2025

Contents

Get Post C - V patton (Controller - View)WEB-INF 폴더(보안폴더) 내의 파일 찾기 Redirection M - C - V patton (Model - Controller - View)

Get

‼️

select (get요청) request의 핵심 method 주소에 붙이는 데이터 -> where에 걸린다

➡ localhost:8080/good.do 의 Request Header에 있는 “User-Agent” 와 “Host” 확인해보기

DemoServlet


package org.example.demo6;

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("*.do")
public class DemoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // select (get요청)
        // request의 핵심 method
        // 주소에 붙이는 데이터 -> where에 걸린다
        String method = req.getHeader("User-Agent");
        System.out.println("User-Agent:" + method);
        String Host = req.getHeader("Host");
        System.out.println("Host:" + Host);

    }

✅ 출력 결과

➡ localhost:8080/demo.do?username=ssar&password=1234 를 입력했을 때

path, method, queryString, username, password 가 어떻게 나오는지 확인해보기

DemoServlet


package org.example.demo6;

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;

// localhost:8080/demo.do?username=ssar&password=1234
@WebServlet("*.do")
public class DemoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // select (get요청)
        // request의 핵심 method
        // 주소에 붙이는 데이터 -> where에 걸린다
        String path = req.getRequestURI();
        System.out.println("path: " + path);

        String method = req.getMethod();
        System.out.println("method: " + method);

        String queryString = req.getQueryString();  // 구체적 질의를 하기 위해 필요 = sql where
        System.out.println("queryString: " + queryString);

        String username = req.getParameter("username"); // 키값을 꺼내서 값을 얻을때
        System.out.println("username: " + username);

        String password = req.getParameter("password"); // 키값을 꺼내서 값을 얻을때
        System.out.println("password: " + password);


    }

✅ 출력 결과

➡ Request에 있는 정보 확인해보기

DemoServlet


package org.example.demo6;

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("*.do")
public class DemoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        Enumeration<String> headerNames = req.getHeaderNames();

        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            String headerValue = req.getHeader(headerName);
            System.out.println(headerName + ": " + headerValue);
        }
    }

✅ 출력 결과

⬇Request 에 들어있는 정보


host: localhost:8080
connection: keep-alive
sec-ch-ua: "Chromium";v="134", "Not:A-Brand";v="24", "Google Chrome";v="134"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"
upgrade-insecure-requests: 1
user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36
accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
sec-fetch-site: none
sec-fetch-mode: navigate
sec-fetch-user: ?1
sec-fetch-dest: document
accept-encoding: gzip, deflate, br, zstd
accept-language: ko-KR,ko;q=0.9,en-US;q=0.8,en;q=0.7

Post

DemoServlet


// insert
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String body = "";

        BufferedReader br = req.getReader();

        while (true) {
            String line = br.readLine();
            if (line == null) break;

            body = body + line;
        }
        System.out.println("body: " + body);


    }
}

➡ Postman에서 text로 입력해보기

✅ 출력 결과

⬇ body에 text가 그대로 담긴다

➡ Postman에서 x-www-formurlencoded로 key, value 넣기

username=ssar 과 password=1234 가 &로 결합되어 ‘username=ssar&password=1234’ 로 전송

➡ ‘username=ssar&password=1234’ 라고 들어오면 getParameter()로 파싱이 가능해짐

✅ 출력 결과

DemoServlet


// insert
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

String username = req.getParameter("username");
        String password = req.getParameter("password");
        System.out.println("username: " + username);
        System.out.println("password: " + password);

index.html


<!DOCTYPE html>
<html lang="ko">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <form action="http://localhost:8080/hello.do" method="post" enctype="application/x-www-form-urlencoded">
        <input type="text" placeholder="Enter username" name="username">
        <input type="text" placeholder="Enter password" name="password">
        <button type="submit">전송</button>
    </form>
</body>

</html>

✅ 출력 결과

HomeServlet


package org.example.demo7;

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("/home.jsp")
public class HomeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setHeader("Content-Type", "text/html");
        String name = "홍길동";
        String body = """
                <html>
                <head>
                    <title>Title</title>
                </head>
                <body>
                <h1>Home Page</h1>
                <hr>
                ${name}
                </body>
                </html>
                """.replace("${name}", name);

        resp.getWriter().println(body);
    }
}

home.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>Home Page</h1>
<hr>
<%
    String name = "홍길동";

%>
<%=name%>
</body>
</html>

C - V patton (Controller - View)

FrontController


package org.example.demo8;

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;

// localhost:8080/hello.do?path=a
@WebServlet("*.do")
public class FrontController extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("common logic");
        String path = req.getParameter("path");
        String name = "ssar";
        if (path.equals("a")) {
            req.setAttribute("name", name);
            req.getRequestDispatcher("a.jsp").forward(req, resp);
        } else if (path.equals("b")) {
            req.setAttribute("name", name);
            req.getRequestDispatcher("b.jsp").forward(req, resp);
        } else if (path.equals("c")) {
            req.setAttribute("name", name);
            req.getRequestDispatcher("c.jsp").forward(req, resp);
        } else {

        }
    }
}

a.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>A view</h1>
<%
    String name = (String) request.getAttribute("name");  // object -> String (다운캐스팅)
%>
<h3>값: <%=name%>
</h3>
</body>
</html>

✅ 출력 결과

b.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>B view</h1>
<h3>${name}</h3>
</body>
</html>

✅ 출력 결과

c.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>C view</h1>
<h3>${name}</h3>
</h3>
</body>

✅ 출력 결과

⚠ But, 파일명으로도 찾는 게 가능하다 → Common Logic을 타지 않음

WEB-INF 폴더(보안폴더) 내의 파일 찾기

‼️

파일을 바로 찾는 것은 불가능 → http://localhost:8080/a.jsp (❌)

무조건 단일진입벽(Controller)을 통해 찾는다 → Common Logic 수행

DemoServlet


package org.example.demo9;

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;

// http://localhost:8080/
@WebServlet("/") // '/' 이후의 형태는 모든 요청이 여기로 몰린다 ex) /, /abc, /a, /b, /c ...
public class DemoServlet extends HttpServlet {

    // http://localhost:8080?path=a     /는 생략가능
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // body -> path=값&name=값
        // queryString -> ?path=값&name=값
        String path = req.getParameter("path");

        if (path.equals("a")) {
            req.setAttribute("name", "ssar");
            req.getRequestDispatcher(ViewResolver.viewName("a")).forward(req, resp);
        } else if (path.equals("b")) {
            req.setAttribute("age", 20);
            req.getRequestDispatcher(ViewResolver.viewName("b")).forward(req, resp);
        }
    }
}

ViewResolver


package org.example.demo9;

public class ViewResolver {
    private static final String prefix = "/WEB-INF/views/";
    private static final String suffix = ".jsp";

    public static String viewName(String filename) {
        return prefix + filename + suffix;
    }
}

a.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>a.jsp</h1>
<h3>내 이름은: ${name}</h3>
</body>
</html>

✅ 출력 결과

b.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>b.jsp</h1>
<h3>내 나이는: ${age}</h3>
</body>
</html>

✅ 출력 결과

DispatcherServlet


package org.example.demo10;

import jakarta.servlet.ServletConfig;
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 org.example.demo10.core.ComponentScan;
import org.example.demo10.core.RequestMapping;
import org.example.demo10.core.ViewResolver;

import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Set;

@WebServlet("*.do")
public class DispatcherServlet extends HttpServlet {

    private Set<Object> controllers;

    @Override
    public void init(ServletConfig config) throws ServletException {
        // 1. 컴포넌트 스캔
        ComponentScan componentScan = new ComponentScan(config.getServletContext());
        controllers = componentScan.scanClass("org.example.demo10.controller");
        //System.out.println(controllers.size());
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // localhost:8080/user.do?path=join
        String path = req.getParameter("path");

        // 2. 라우팅
        String templatePath = route(path);

        // 3. 이동
        if (templatePath == null) {
            resp.setStatus(404);
            resp.getWriter().println("<h1>404 Not Found</h1>");
        } else {
            req.getRequestDispatcher(ViewResolver.viewName(templatePath)).forward(req, resp);
        }


    }

    private String route(String path) {
        for (Object instance : controllers) {
            Method[] methods = instance.getClass().getMethods();

            for (Method method : methods) {
                RequestMapping rm = method.getAnnotation(RequestMapping.class);

                if (rm == null) continue; // 다음 for문으로 바로 넘어감

                if (rm.value().equals(path)) {
                    try {
                        return (String) method.invoke(instance);

                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }
                }
            }
        }
        return null;
    }
}

ComponentScan


package org.example.demo10.core;

import jakarta.servlet.ServletContext;

import java.io.File;
import java.util.HashSet;
import java.util.Set;

public class ComponentScan {
    private final ServletContext servletContext;

    public ComponentScan(ServletContext servletContext) {
        this.servletContext = servletContext;
    }

    // 클래스를 스캔하는 메소드
    public Set<Object> scanClass(String pkg) {
        Set<Object> instances = new HashSet<>();
        try {
            // 톰캣의 webapps 폴더 내 WEB-INF/classes 경로 가져오기
            String classPath = servletContext.getRealPath("/WEB-INF/classes/");

            // C:\Program Files\Apache Software Foundation\Tomcat 11.0\webapps\ROOT\WEB-INF\classes\
            File slashDir = new File(classPath);
            File dotToSlashDir = new File(slashDir, pkg.replace(".", File.separator));

            for (File file : dotToSlashDir.listFiles()) {
                //System.out.println(file.getName());

                String className = pkg + "." + file.getName().replace(".class", "");
                //System.out.println(className);

                try {
                    Class cls = Class.forName(className);
                    if (cls.isAnnotationPresent(Controller.class)) {
                        //System.out.println("Controller 어노테이션");
                        Object instance = cls.getDeclaredConstructor().newInstance();
                        instances.add(instance);
                    }
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            }

            return instances;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

}

ViewResolver


package org.example.demo10.core;

public class ViewResolver {
    private static final String prefix = "/WEB-INF/views/";
    private static final String suffix = ".jsp";

    public static String viewName(String filename) {
        return prefix + filename + suffix;
    }
}

UserController


package org.example.demo10.controller;

import org.example.demo10.core.Controller;
import org.example.demo10.core.RequestMapping;

@Controller
public class UserController {

    @RequestMapping("join")
    public String join() {
        System.out.println("UserController join");
        return "join";
    }

    @RequestMapping("login")
    public String login() {
        System.out.println("UserController login");
        return "login";
    }
}

BoardController


package org.example.demo10.controller;

import org.example.demo10.core.Controller;

@Controller
public class BoardController {
}

Annotation / @Controller


package org.example.demo10.core;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface Controller {
}

Annotation / @RequestMapping


package org.example.demo10.core;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface RequestMapping {
    String value();
}

join.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>join page</h1>
</body>
</html>

✅ 출력 결과

login.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>login page</h1>
</body>
</html>

✅ 출력 결과

templatePath == null

➡ path가 ‘join’ 이나 ‘login’ 이 아니면

resp.setStatus(404);
            resp.getWriter().println("<h1>404 Not Found</h1>");

✅ 출력 결과

Redirection

DispatcherServlet


package org.example.demo10;

import jakarta.servlet.ServletConfig;
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 org.example.demo10.core.ComponentScan;
import org.example.demo10.core.RequestMapping;
import org.example.demo10.core.ViewResolver;

import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Set;

@WebServlet("*.do")
public class DispatcherServlet extends HttpServlet {

    private Set<Object> controllers;

    @Override
    public void init(ServletConfig config) throws ServletException {
        // 1. 컴포넌트 스캔
        ComponentScan componentScan = new ComponentScan(config.getServletContext());
        controllers = componentScan.scanClass("org.example.demo10.controller");
        //System.out.println(controllers.size());
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // localhost:8080/user.do?path=join
        String path = req.getParameter("path");

        // 2. 라우팅
        String templatePath = route(path);

        // 3. redirection
        // localhost:8080/user.do?path=login
        if (templatePath.contains("redirect:")) {
            String redirectPath = templatePath.replace("redirect:", "");  // home
//            resp.setStatus(302);
//            resp.setHeader("Location", "?path=" + redirectPath);
            resp.sendRedirect("?path=" + redirectPath);
            return;  // 밑으로 안 내려가게 여기서 종료
        }

        // 4. 이동
        if (templatePath == null) {
            resp.setStatus(404);
            resp.getWriter().println("<h1>404 Not Found</h1>");
        } else {
            req.getRequestDispatcher(ViewResolver.viewName(templatePath)).forward(req, resp);
        }


    }

    private String route(String path) {
        for (Object instance : controllers) {
            Method[] methods = instance.getClass().getMethods();

            for (Method method : methods) {
                RequestMapping rm = method.getAnnotation(RequestMapping.class);

                if (rm == null) continue; // 다음 for문으로 바로 넘어감

                if (rm.value().equals(path)) {
                    try {
                        return (String) method.invoke(instance);

                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }
                }
            }
        }
        return null;
    }
}

home.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>home page</h1>
</body>
</html>

➡ http://localhost:8080/hello.do?path=login 입력하면?

➡ http://localhost:8080/hello.do?path=home 으로 redirect

BoardController


package org.example.hello.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;


@Controller
public class BoardController {

    // localhost:8080/detail
    @GetMapping("/detail")
    public String detail() {
        return "detail";
    }


    // localhost:8080/home
    @GetMapping("/home")
    public String home() {
        return "home";
        
    }

}

UserController


package org.example.hello.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;

@Controller
public class UserController {

    // 줄게 -> 회원가입 정보
    // localhost:8080/join
    // body : username=ssar
    // header : Content-Type : application/x-www-form-urlencoded
    @PostMapping("/join")
    public String join(String username) {
        // 1. DB insert
        System.out.println("username: " + username);
        // 2. 응답
        return "redirect:/home";
    }

    // 줘 -> 회원가입 페이지
    @GetMapping("/join-form")
    public String joinForm() {
        return "join-form";
    }
}

join-form.mustache


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>회원가입 페이지</h1>
<form action="/join" method="post">
    <input type="text" name="username" placeholder="Enter username">
    <button type="sumit">회원가입</button>
</form>
</body>
</html>

⬇ input tag에 ‘ssar’을 입력하면?

⬇ redirection 되서 home 으로 이동

home.mustache


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>홈 페이지</h1>
</body>
</html>

detail.mustache


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>상세보기 페이지</h1>
</body>
</html>

M - C - V patton (Model - Controller - View)

Contents

Get Post C - V patton (Controller - View)WEB-INF 폴더(보안폴더) 내의 파일 찾기 Redirection M - C - V patton (Model - Controller - View)