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back-end/서블릿

서블릿 이용 계산기(저장용)

by Ryuuu 2021. 6. 29.

JSP를 학습하기 전 서블릿만 이용해서 계산기를 만들어 보았다.

매우 무식한 방법일지도 모르나 이렇게 하면 JSP사용하는 이유를 나중에 더 알 수 있대서 이렇게 만들었다.

백스페이스나 몇개 귀찮아서 기능 구현 안한거도 있긴하다.

그냥 지울라면 C나 CE누르면 됨

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package com.ryuuu.web;
 
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;
 
import org.graalvm.polyglot.Context;
@WebServlet("/calc_page")
public class calcpage extends HttpServlet{ 
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse rsp) throws ServletException, IOException {
        Cookie[] cookies = req.getCookies();
        PrintWriter out = rsp.getWriter();
         
        //입력 인자들 가지고옴
        String value = req.getParameter("value");
        String op = req.getParameter("oper");
        String dot = req.getParameter("dot");
         
        String exp = "";
         
        //쿠키에 저장한 계산식 가지고옴
        if(cookies != null) {
            for (Cookie c : cookies) {
                if(c.getName().equals("exp")) {
                    exp = c.getValue();
                    break;
                }
            }
        }
         
        // = 누르면 계산
        if(op != null && op.equals("=")) {
            try (Context context = Context.create("js")) {
                exp = String.valueOf(context.eval("js",exp));
            } catch (Exception e) {
                System.err.println();
            }
        }
         
        // = 아니면 계산식에 이어줌
        else {
            exp += (value == null)? "" : value;
            exp += (op == null)? "" : op;
            exp += (dot == null)? "" : dot;
        }
        Cookie expCookie = new Cookie("exp", exp);
        if(op != null &&(op.equals("CE") || op.equals("C"))) {
            expCookie.setMaxAge(0);
        }
        rsp.addCookie(expCookie);
        rsp.sendRedirect("calc_page");
    }
 
@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse rsp) throws ServletException, IOException {
    Cookie[] cookies = req.getCookies();
    String exp = "0";
    //계산식 쿠키 가지고옴
    if(cookies != null) {
        for (Cookie c : cookies) {
            if(c.getName().equals("exp")) {
                exp = c.getValue();
                break;
            }
        }
    }
     
    PrintWriter out = rsp.getWriter();
     
    out.write("<!DOCTYPE html>");
    out.write("<html>");
    out.write("<head>");
    out.write("<meta charset=\"EUC-KR\">");
    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 method=\"post\">");
    out.write("<table>");
    out.write("<tr>");
    out.printf("<td class = \"output\" colspan=\"4\">%s</td>",exp);    
    out.write("</tr>");
    out.write("<tr>");
    out.write("<td><input type=\"submit\" name = \"oper\" value=\"CE\"></td>");
    out.write("<td><input type=\"submit\" name = \"oper\" value=\"C\"></td>");
    out.write("<td><input type=\"submit\" name = \"oper\" value=\"BS\"></td>");
    out.write("<td><input type=\"submit\" name = \"oper\" 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 = \"oper\" 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 = \"oper\" 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 = \"oper\" 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 = \"oper\" value=\"=\"></td>");
    out.write("</tr>");
    out.write("</table>");
    out.write("</form>");
    out.write("</body>");
    out.write("</html>");
     
    }
     
}
저작자표시 비영리 (새창열림)

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