Forwarding

PreviousFrontController패턴 Command 패턴 NextMVC

Last updated 4 years ago

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Forwarding

서블릿 또는 JSP에서 요청을 받은 후에 다른 component로 요청을 위임할 수 있다. 그것을 포워딩이라한다.

포워딩 방법에는 2개의 클래스(RequestDispatcher, HttpServletResponse)를 이용한다.

RequestDispatcher 클래스

요청받은 요청객체(request)를 위임받는 컴포넌트(S2)에 동일하게 전달할 수 있다.

예제

dispatcher.jsp

<%@ page language="java" contentType="text/html; charset=EUC-KR"
    pageEncoding="EUC-KR"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=EUC-KR">
<title>Insert title here</title>
</head>
<body>

        dispacherJsp.jsp
        <hr />

        id : <%= request.getAttribute("id") %> <br />
        pw : <%= request.getAttribute("pw") %>

</body>
</html>

RequestObj.java

package com.javalec.ex;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RequestObj
 */
@WebServlet("/RequestObj")
public class RequestObj extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public RequestObj() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("doGet");
        actionDo(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("doPost");
        actionDo(request, response);
    }

    private void actionDo(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("actionDo");

        request.setAttribute("id", "abcde");
        request.setAttribute("pw", "12345");

        RequestDispatcher dispatcher = request.getRequestDispatcher("/dispacherJsp.jsp");
        dispatcher.forward(request, response);

    }
}

RequestDispatcher dispatcher = request.getRequestDispatcher("/dispacherJsp.jsp");
dispatcher.forward(request, response);

클라이언트가 준 request객체에서 getRequestDispatcher("위임받을 컴포넌트") 로 생성해준다.

dispatcher.forward 로 전달해준다. 두 파일에서 사용하는 파일이 동일한 request라는 것을 확인할 수 있다.

HttpServletResponse 클래스

Request를 위임하는 클래스이다. 하지만 RequestDispatcher 클래스와의 차이점은 요청받은 객체를 위임 받는 컴포넌트에 전달하는 것이 아닌 새로운 객체를 생성한다.

예제

JSP

<%@ page language="java" contentType="text/html; charset=EUC-KR"
    pageEncoding="EUC-KR"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=EUC-KR">
<title>Insert title here</title>
</head>
<body>

        <%
            request.setAttribute("id", "abcde");
            request.setAttribute("pw", "12345");

            response.sendRedirect("RequestObj");
        %>

</body>
</html>

response.sendRedirect("RequestObj"); 가 HttpServletResponse 객체이다.

RequestObj.java

package com.javalec.ex;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RequestObj
 */
@WebServlet("/RequestObj")
public class RequestObj extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public RequestObj() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("doGet");
        actionDo(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("doPost");
        actionDo(request, response);
    }

    private void actionDo(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("actionDo");

        String id = (String)request.getAttribute("id");
        String pw = (String)request.getAttribute("pw");

        response.setContentType("text/jhtml; charset=EUC-KR");
        PrintWriter writer = response.getWriter();
        writer.print("<html><head></head><body>");
        writer.print("RequestObj" + "<hr />");
        writer.print("id : " + id + "<br />");
        writer.print("pw : " + pw);
        writer.print("</body></html>");

    }
}

id: null
pw: null

null값이 뜨는 것을 볼 수 있다. 위임을 한다고 해서 바로 전달되는 것이 아니라 클라이언트가 다시 위임 받은 컴포넌트를 요청한다. 새로운 객체가 생성되어 전달되므로 요청받은 컴포넌트에 setAttribute 해준 값은 위임받은 Component로 전달되지 않는다.

PreviousFrontController패턴 Command 패턴 NextMVC

Last updated 4 years ago

Was this helpful?

서블릿 또는 JSP에서 요청을 받은 후에 다른 component로 요청을 위임할 수 있다. 그것을 포워딩이라한다.

포워딩 방법에는 2개의 클래스(RequestDispatcher, HttpServletResponse)를 이용한다.

RequestDispatcher 클래스

요청받은 요청객체(request)를 위임받는 컴포넌트(S2)에 동일하게 전달할 수 있다.

예제

dispatcher.jsp

<%@ page language="java" contentType="text/html; charset=EUC-KR"
    pageEncoding="EUC-KR"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=EUC-KR">
<title>Insert title here</title>
</head>
<body>

        dispacherJsp.jsp
        <hr />

        id : <%= request.getAttribute("id") %> <br />
        pw : <%= request.getAttribute("pw") %>

</body>
</html>

RequestObj.java

package com.javalec.ex;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RequestObj
 */
@WebServlet("/RequestObj")
public class RequestObj extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public RequestObj() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("doGet");
        actionDo(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("doPost");
        actionDo(request, response);
    }

    private void actionDo(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("actionDo");

        request.setAttribute("id", "abcde");
        request.setAttribute("pw", "12345");

        RequestDispatcher dispatcher = request.getRequestDispatcher("/dispacherJsp.jsp");
        dispatcher.forward(request, response);

    }
}

RequestDispatcher dispatcher = request.getRequestDispatcher("/dispacherJsp.jsp");
dispatcher.forward(request, response);

클라이언트가 준 request객체에서 getRequestDispatcher("위임받을 컴포넌트") 로 생성해준다.

dispatcher.forward 로 전달해준다. 두 파일에서 사용하는 파일이 동일한 request라는 것을 확인할 수 있다.

HttpServletResponse 클래스

예제

JSP

<%@ page language="java" contentType="text/html; charset=EUC-KR"
    pageEncoding="EUC-KR"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=EUC-KR">
<title>Insert title here</title>
</head>
<body>

        <%
            request.setAttribute("id", "abcde");
            request.setAttribute("pw", "12345");

            response.sendRedirect("RequestObj");
        %>

</body>
</html>

response.sendRedirect("RequestObj"); 가 HttpServletResponse 객체이다.

RequestObj.java

package com.javalec.ex;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RequestObj
 */
@WebServlet("/RequestObj")
public class RequestObj extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public RequestObj() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("doGet");
        actionDo(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("doPost");
        actionDo(request, response);
    }

    private void actionDo(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("actionDo");

        String id = (String)request.getAttribute("id");
        String pw = (String)request.getAttribute("pw");

        response.setContentType("text/jhtml; charset=EUC-KR");
        PrintWriter writer = response.getWriter();
        writer.print("<html><head></head><body>");
        writer.print("RequestObj" + "<hr />");
        writer.print("id : " + id + "<br />");
        writer.print("pw : " + pw);
        writer.print("</body></html>");

    }
}

id: null
pw: null