[스프링 MVC 1편] #3. 서블릿, JSP, MVC 패턴 (1) #222

chaelink · 2024-05-11T08:32:59Z

chaelink
May 11, 2024

섹션 3. 서블릿, JSP, MVC 패턴 (1)

1. 회원 관리 웹 애플리케이션 요구사항

회원 정보 : 이름 username, 나이 age

기능 요구사항 : 회원 저장, 회원 목록 조회

회원 도메인 모델

public class Member {
    
    private Long id;
    private String username;
    private int age;
    
    public Member() {
    }
    
    public Member(String username, int age) {
        this.username = username;
        this.age = age;
    }
}

회원 저장소

public class MemberRepository {

    private static Map<Long, Member> store = new HashMap<>();

    private static long sequence = 0L; //static 사용

    private static final MemberRepository instance = new MemberRepository();

    public static MemberRepository getInstance() {
        return instance;
    }

    private MemberRepository() {
    }

    public Member save(Member member) {
        member.setId(++sequence);
        store.put(member.getId(), member);
        return member;
    }

    public Member findfById(Long id) {
        return store.get(id);
    }

    public List<Member> findAll() {
        return new ArrayList<>(store.values());
    }

    public void clearStore() {
        store.clear();
    }

}

private 으로 instance를 생성하여 회원 저장소에 싱글톤 패턴 적용 ( 스프링을 사용하면 스프링 빈으로 등록되지만 여기서는 최대한 스프링 없이 구현)

회원 저장소 테스트

class MemberRepositoryTest {

    MemberRepository memberRepository = MemberRepository.getInstance();

    @AfterEach
    void afterEach() {
        memberRepository.clearStore();
    }

    @Test
    void save() {
        //given
        Member member = new Member("hello", 20);

        //when
        Member savedMember = memberRepository.save(member);

        //then
        Member findMember = memberRepository.findfById(savedMember.getId());
        Assertions.assertThat(findMember).isEqualTo(savedMember);

    }

    @Test
    void findAll() {
        //given
        Member member1 = new Member("member1", 20);
        Member member2 = new Member("member2", 30);

        memberRepository.save(member1);
        memberRepository.save(member2);

        //when
        List<Member> result = memberRepository.findAll();

        //then
        Assertions.assertThat(result.size()).isEqualTo(2);
        Assertions.assertThat(result).contains(member1,member2);
    }
}

2. 서블릿으로 회원 관리 웹 애플리케이션 만들기

회원 등록 HTML 폼

@WebServlet(name = "memberFormServlet", urlPatterns = "/servlet/members/new-form")
public class MemberFormServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse
            response)
            throws ServletException, IOException {
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
        PrintWriter w = response.getWriter();
        w.write("<!DOCTYPE html>\n" +
                "<html>\n" +
                "<head>\n" +
                "    <meta charset=\"UTF-8\">\n" +
                "    <title>Title</title>\n" +
                "</head>\n" +
                "<body>\n" +
                "<form action=\"/servlet/members/save\" method=\"post\">\n" +
                "    username: <input type=\"text\" name=\"username\" />\n" +
                "    age:      <input type=\"text\" name=\"age\" />\n" +
                "    <button type=\"submit\">전송</button>\n" +
                "</form>\n" +
                "</body>\n" +
                "</html>\n");
    }
}

단순히 회원 정보를 저장하는 HTML FORM, 전달 받는 서블릿도 별도로 만들어야 한다.

회원 저장 서블릿

@WebServlet(name = "memberSaveServlet", urlPatterns = "/servlet/members/save")
public class MemberSaveServlet extends HttpServlet {

    private MemberRepository memberRepository = MemberRepository.getInstance();

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

        System.out.println("MemberSaveServlet.service");
        String username = request.getParameter("username");
        int age = Integer.parseInt(request.getParameter("age"));
        Member member = new Member(username, age);
        System.out.println("member = " + member);
        memberRepository.save(member);
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
        PrintWriter w = response.getWriter();

        w.write("<html>\n" +
                "<head>\n" +
                "    <meta charset=\"UTF-8\">\n" +
                "</head>\n" +
                "<body>\n" +
                "성공\n" +
                "<ul>\n" +
                "    <li>id="+member.getId()+"</li>\n" +
                "    <li>username="+member.getUsername()+"</li>\n" +
                "    <li>age="+member.getAge()+"</li>\n" +
                "</ul>\n" +
                "<a href=\"/index.html\">메인</a>\n" +
                "</body>\n" +
                "</html>");
    }
}

MemberSaveServlet 동작 순서

파라미터를 조회해서 Member 객체 생성
Member객체를 MemberRepository를 통해서 저장
Member 객체를 사용해서 결과 화면용 HTML 동적 생성, 응답

회원 목록 조회

@WebServlet(name = "memberListServlet", urlPatterns = "/servlet/members")
 public class MemberListServlet extends HttpServlet {
 private MemberRepository memberRepository = MemberRepository.getInstance();
    @Override
 protected void service(HttpServletRequest request, HttpServletResponse 
response)
 throws ServletException, IOException {
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
 List<Member> members = memberRepository.findAll();
 PrintWriter w = response.getWriter();
        w.write("<html>");
        w.write("<head>");
        w.write("    <meta charset=\"UTF-8\">");
        w.write("    <title>Title</title>");
        w.write("</head>");
        w.write("<body>");
        w.write("<a href=\"/index.html\">[메인](https://github.com/%22/index.html/%22)</a>");
        w.write("<table>");
        w.write("    <thead>");
        w.write("    <th>id</th>");
        w.write("    <th>username</th>");
        w.write("    <th>age</th>");
        w.write("    </thead>");
        w.write("    <tbody>");
 /*
        w.write("    <tr>");
        w.write("        <td>1</td>");
        w.write("        <td>userA</td>");
        w.write("        <td>10</td>");
        w.write("    </tr>");
 */
 }
 for (Member member : members) {
            w.write("    <tr>");
            w.write("        <td>" + member.getId() + "</td>");
            w.write("        <td>" + member.getUsername() + "</td>");
            w.write("        <td>" + member.getAge() + "</td>");
            w.write("    </tr>");
        }
        w.write("    </tbody>");
        w.write("</table>");
        w.write("</body>");
        w.write("</html>");
    }

MemberListServlet 동작 순서

memberRepository.findAll()을 통해 모든 회원 조회
회원 목록 HTML을 for 루프를 통해서 회원 수 만큼 동적으로 생성하고 응답

3. JSP로 회원 관리 웹 애플리케이션 만들기

JSP 라이브러리 추가
build.gradle

//JSP 추가 시작
implementation 'org.apache.tomcat.embed:tomcat-embed-jasper'
 implementation 'jakarta.servlet:jakarta.servlet-api' //스프링부트 3.0 이상
implementation 'jakarta.servlet.jsp.jstl:jakarta.servlet.jsp.jstl-api' //스프링부트 
3.0 이상
implementation 'org.glassfish.web:jakarta.servlet.jsp.jstl' //스프링부트 3.0 이상
//JSP 추가 끝

회원 등록 폼 JSP

<%@ page contentType="text/html;charset=UTF-8" language="java" %> //첫 줄은 JSP 문서라는 의미
 <html>
 <head>
    <title>Title</title>
 </head>
 <body>

 <form action="/jsp/members/save.jsp" method="post">
    username: <input type="text" name="username" />
    age:      <input type="text" name="age" />
    <button type="submit">전송</button>
 </form>
 </body>
</html>

첫 줄을 제외하고는 HTML과 완전히 똑같다. JSP는 서버 내부에서 서블릿으로 변환되는데, 우리가 만들었던 MemberFormServlet과 거의 유사하다

회원 저장 JSP

<%@ page import="hello.servlet.domain.member.MemberRepository" %>
 <%@ page import="hello.servlet.domain.member.Member" %>
 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 <%
 //    request, response 사용 가능
    MemberRepository memberRepository = MemberRepository.getInstance();
    System.out.println("save.jsp");
    String username = request.getParameter("username");
    int age = Integer.parseInt(request.getParameter("age"));
    Member member = new Member(username, age);
    System.out.println("member = " + member);
    memberRepository.save(member);
 %>
 <html>
 <head>
    <meta charset="UTF-8">
 </head>
 <body>
성공
<ul>
    <li>id=<%=member.getId()%></li>
    <li>username=<%=member.getUsername()%></li>
    <li>age=<%=member.getAge()%></li>
 </ul>
 <a href="/index.html">[메인](https://github.com/index.html)</a>
 </body>
 </html>

JSP는 자바 코드 그대로 사용 가능

회원 목록 JSP

<html>
<body>
<!--StartFragment--><%@ page import="java.util.List" %>
 <%@ page import="hello.servlet.domain.member.MemberRepository" %>
 <%@ page import="hello.servlet.domain.member.Member" %>
 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 <%
    MemberRepository memberRepository = MemberRepository.getInstance();
    List<Member> members = memberRepository.findAll();
 %>
 <html>
 <head>
    
    <title>Title</title>
 </head>
 <body>
 <a href="/index.html">메인</a>
 
id | username | age
-- | -- | --
" + member.getId() + " | " + member.getUsername() + " | " + member.getAge() + "


 </body>
 </html><!--EndFragment-->
</body>
</html>
<%@ page import="java.util.List" %>
 <%@ page import="hello.servlet.domain.member.MemberRepository" %>
 <%@ page import="hello.servlet.domain.member.Member" %>
 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 <%
    MemberRepository memberRepository = MemberRepository.getInstance();
    List<Member> members = memberRepository.findAll();
 %>
 <html>
 <head>
    <meta charset="UTF-8">
    <title>Title</title>
 </head>
 <body>
 <a href="/index.html">[메인](https://github.com/index.html)</a>
 <table>
    <thead>
    <th>id</th>
    <th>username</th>
    <th>age</th>
    </thead>
    <tbody>
 <%
 %>
    for (Member member : members) {
        out.write("    <tr>");
        out.write("        <td>" + member.getId() + "</td>");
        out.write("        <td>" + member.getUsername() + "</td>");
        out.write("        <td>" + member.getAge() + "</td>");
        out.write("    </tr>");
    }
    </tbody>
 </table>
 </body>
 </html>

회원 리포지토리 먼저 조회 후, 결과 List 사용하여 태그를 반복 출력

서블릿과 JSP의 한계

서블릿 : 뷰(View)화면을 위한 HTML을 만드는 작업이 자바 코드에 섞여 지저분하고 복잡함
JSP : 뷰를 생성하는 HTML 작업을 깔끔하게 가져가고, 중간중간 동적으로 변경이 필요한 부분에만 자
바 코드를 적용. 그런데 이렇게 해도 해결되지 않는 몇가지 고민이 남는다.

코드를 잘 보면, JAVA 코드, 데이터를 조회하는 리포지토리 등등 다양한 코드가 모두 JSP에 노출되어 있다.
JSP가 너무 많은 역할을 한다.

MVC 패턴 등장
비즈니스 로직은 서블릿 처럼 다른곳에서 처리하고,
JSP는 목적에 맞게 HTML로 화면(View)을 그리는 일에 집중하도록 하자.
과거 개발자들도 모두 비슷한 고민이 있었고, 그래서 MVC 패턴이 등장했다. 우리도 직접 MVC 패턴을 적용해
서 프로젝트를 리팩터링 해보자

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[스프링 MVC 1편] #3. 서블릿, JSP, MVC 패턴 (1) #222

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chaelink May 11, 2024

섹션 3. 서블릿, JSP, MVC 패턴 (1)

1. 회원 관리 웹 애플리케이션 요구사항

2. 서블릿으로 회원 관리 웹 애플리케이션 만들기

3. JSP로 회원 관리 웹 애플리케이션 만들기

Replies: 0 comments

chaelink
May 11, 2024