[Servlet] forward, sendRedirect

 

 

 

 forward 

ServletTest1

package servlet;


import java.io.IOException;

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


@WebServlet("/test1")
public class ServletTest extends HttpServlet {
	private static final long serialVersionUID = 1L;


	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		// request
		request.setAttribute("requestData", "dataR");

		// context
		ServletContext context = request.getServletContext();
		context.setAttribute("contextData", "dataC");

		// session
		HttpSession session = request.getSession();
		session.setAttribute("sessionData", "dataS");

		// forwarding 하기
		RequestDispatcher disp = request.getRequestDispatcher("/test2");
		disp.forward(request, response);

		System.out.println(request.getRequestURL());

	}


	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		doGet(request, response);
	}

}

request 을 통해서 forwarding 을 할 수 있습니다.

 

ServletTest2

package servlet;


import java.io.IOException;

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


@WebServlet("/test2")
public class ServletTest2 extends HttpServlet {
	private static final long serialVersionUID = 1L;


	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		// request
		String requestData = (String) request.getAttribute("requestData");

		// context
		ServletContext context = request.getServletContext();
		String contextData = (String) context.getAttribute("contextData");

		// session
		HttpSession session = request.getSession();
		String sessionData = (String) session.getAttribute("sessionData");

		System.out.println(request.getRequestURL());
		response.getWriter().write("requestData: " + requestData);
		response.getWriter().write("\ncontextData: " + contextData);
		response.getWriter().write("\nsessionData: " + sessionData);
	}


	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		doGet(request, response);
	}

}

출력

해당 path 로 url 변경 없이 넘어가게 됩니다. request 데이터를 그대로 담고 넘어갑니다.

 

 

 sendRedirect 

ServletTest1

package servlet;


import java.io.IOException;

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


@WebServlet("/test1")
public class ServletTest extends HttpServlet {
	private static final long serialVersionUID = 1L;


	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		// request
		request.setAttribute("requestData", "dataR");

		// context
		ServletContext context = request.getServletContext();
		context.setAttribute("contextData", "dataC");

		// session
		HttpSession session = request.getSession();
		session.setAttribute("sessionData", "dataS");

		// sendRedirect 하기
		response.sendRedirect(request.getContextPath() + "/test2");

		System.out.println(request.getRequestURL());

	}


	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		doGet(request, response);
	}

}

response.sendRedirect(location) 으로 페이지를 이동시킬 수 있습니다.

path 가 아니라 location 이기 때문에 contextPath 까지 붙여야 이동하고 싶은 앱내  페이지로 이동을 합니다.

 

ServletTest2

package servlet;


import java.io.IOException;

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


@WebServlet("/test2")
public class ServletTest2 extends HttpServlet {
	private static final long serialVersionUID = 1L;


	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		// request
		String requestData = (String) request.getAttribute("requestData");

		// context
		ServletContext context = request.getServletContext();
		String contextData = (String) context.getAttribute("contextData");

		// session
		HttpSession session = request.getSession();
		String sessionData = (String) session.getAttribute("sessionData");

		System.out.println(request.getRequestURL());
		response.getWriter().write("requestData: " + requestData);
		response.getWriter().write("\ncontextData: " + contextData);
		response.getWriter().write("\nsessionData: " + sessionData);
	}


	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		doGet(request, response);
	}

}

출력

response 로 sendRedirect() 하는 것이기 때문에 request 에 세팅한 데이터는 없어지게 됩니다.

왜냐하면 request 는 하나의 response 를 만나면 소멸이 됩니다.

 

 

 

 

 

 

 

 

 

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