JSP - NewLecture - redirection, 계산기프로그램을 이용한 동적페이지 만들기/쿠키삭제하기

31 Mar 2021

🔷 NewLecture - redirection, 계산기프로그램을 이용한 동적페이지 만들기/쿠키삭제하기

✔ redirection

- 서버에서 페이지를 전환해준다

✔ 계산기프로그램을 이용한 동적페이지 만들기/쿠키삭제하기

화면출력 코드

  package newlecture;

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

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

  /**
  * Servlet implementation class add
  */
  @WebServlet("/calcpage")
  public class calcPage extends HttpServlet {
        
      protected void service(HttpServletRequest request, HttpServletResponse response) throws IOException {
            
          //쿠키 배열변수 선언
                  Cookie[] cookies = request.getCookies();	
                    
          // 쿠키 읽어오는 연산식
          String exp="0";	
          if(cookies !=null) { // 쿠키가 null이 아닐경우
              for(Cookie c : cookies) { // 연산식 실행
                  if(c.getName().equals("exp")) {
                      exp =c.getValue();
                      break;
                      }
                  }
          }
            

          response.setCharacterEncoding("UTF-8");
          response.setContentType("text/html; charset=UTF-8");
          PrintWriter out = response.getWriter();

  // 동적으로 만들었다
  out.write("<!DOCTYPE html>");
  out.write("<html>");
  out.write("<head>");
  out.write("<meta charset=\"UTF-8\"> ");
  out.write("<title>calc</title>");
  out.write("<style>");
  out.write("input{");
  out.write("	width : 50px;");
  out.write("	height : 50px;");
  out.write("}");
  out.write(".output{");
  out.write("height : 50px;");
  out.write("background : #e9e9e9;");
  out.write("font-size:24px;");
  out.write("font-weight : bold;");
  out.write("text-align : right;");
  out.write("padding : 0px, 5px;");
  out.write("}");
  out.write("</style>");
  out.write("</head>");
  out.write("<body>");
  out.write("<form action=\"calc3\" method=\"post\">");
  out.write("<table>");
  out.write("<tr>");
  out.printf(		"<td class=\"output\" colspan=\"4\">%s</td>",exp); // exp 출력
  out.write("</tr>");
  out.write("<tr>");
  out.write("<td><input type=\"submit\" name=\"operator\" value=\"CE\" /></td>");
  out.write("<td><input type=\"submit\" name=\"operator\" value=\"C\" /></td>");
  out.write("<td><input type=\"submit\" name=\"operator\" value=\"BS\" /></td>");
  out.write("<td><input type=\"submit\" name=\"operator\" value=\"/\" /></td>");
  out.write("</tr>");
  out.write("<tr>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"7\" /></td>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"8\" /></td>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"9\" /></td>");
  out.write("<td><input type=\"submit\" name=\"operator\" value=\"*\" /></td>");
  out.write("</tr>");
  out.write("<tr>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"4\" /></td>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"5\" /></td>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"6\" /></td>");
  out.write("<td><input type=\"submit\" name=\"operator\" value=\"-\" /></td>");
  out.write("</tr>");
  out.write("<tr>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"1\" /></td>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"2\" /></td>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"3\" /></td>");
  out.write("<td><input type=\"submit\" name=\"operator\" value=\"+\" /></td>");
  out.write("</tr>");
  out.write("<tr>");
  out.write("<td></td>");
  out.write("<td><input type=\"submit\" name=\"value\" value=\"0\" /></td>");
  out.write("<td><input type=\"submit\" name=\"dot\" value=\".\" /></td>");
  out.write("<td><input type=\"submit\" name=\"operator\" value=\"=\" /></td>");
  out.write("</tr>");
  out.write("</table>");
  out.write("</form>");
  out.write("</body>");
  out.write("</html>");
      }

  }

계산코드

  package newlecture;

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

  import javax.script.ScriptEngine;
  import javax.script.ScriptEngineManager;
  import javax.script.ScriptException;
  import javax.servlet.ServletContext;
  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.Cookie;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import javax.servlet.http.HttpSession;

  /**
  * Servlet implementation class add
  */
  @WebServlet("/calc3")
  public class calc3 extends HttpServlet {
      private static final long serialVersionUID = 1L;
        
      /**
      * @see HttpServlet#HttpServlet()
      */
      public calc3() {
          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
          response.getWriter().append("Served at: ").append(request.getContextPath());
      }

      /**
      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
      */
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          //쿠키 배열변수 선언
          Cookie[] cookies = request.getCookies();	
            
          // 사용자가 입력한 값을 가지고
          String value = request.getParameter("value");
          String operator = request.getParameter("operator");
          String dot = request.getParameter("dot");
            
          // 쿠키를 만들어 exp로 전달한다
          String exp ="";
          // 쿠키 읽어오는연산식
          if(cookies !=null) { // 쿠키가 null이 아닐경우
              for(Cookie c : cookies) { // 연산식 실행
                  if(c.getName().equals("exp")) {
                      exp =c.getValue();
                      break;
                      }
                  }
          }
          if(operator !=null && operator.equals("=")) {
                
              // 계산
              // javaScript 구문 실행 객체 생성
              ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
              try {
                  exp = String.valueOf(engine.eval(exp));
              } catch (ScriptException e) {
                  // TODO Auto-generated catch block
                  e.printStackTrace();
              }
          }else if(operator !=null && operator.equals("C")) { // 쿠키 삭제 : C버튼클릭 시 초기화
              exp = "";
          }
          else {
              // 입력값 누적
              exp += (value == null) ? "" : value;
              exp += (operator == null) ? "" : operator;
              exp += (dot == null) ? "" : dot;
          }

            
            
          // 쿠키생성
          Cookie expCookie = new Cookie("exp",exp);
          if(operator !=null && operator.equals("C")) { // 조건에 해당 될 때만
              expCookie.setMaxAge(0); // 쿠키삭제(브라우저에서)
          }
          // 쿠키로 저장
          response.addCookie(expCookie);
            
          // redirection 기능 : 페이지 이동기능 => +,-연산시 빈페이지 전달받지않음
          response.sendRedirect("calcpage");
          }
      }

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