back-end/서블릿
서블릿 이용 계산기(저장용)
Ryuuu
2021. 6. 29. 23:51
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
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>");
}
}