🔷 NewLecture - GET/POST 합치기, MVC model1, MVC model2, EL객체
✔ GET/POST 합치기(계산기 프로그램)
- 코드
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.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; // get,post 합치기 @WebServlet("/calculator") public class calculator extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, 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 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>"); } @Override 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) } expCookie.setPath("/calculator"); // 쿠키로 저장 response.addCookie(expCookie); response.sendRedirect("calculator"); } }
▶ 출력 
✔ MVC model1
- Model : 출력데이터
- Controller : 입력과 제어를 담당 ( 자바코드 )
- View : 출력담당 (HTML 코드)
- 컨트롤러와 뷰가 물리적으로 분리되지 않은 방식이다
✔ MVC model2
- 컨트롤러와 뷰가 물리적으로 분리된 방식
- Dispatcher를 집중화 한 후의 모델
✔ EL(Expression Language)
- 저장 객체에서 값을 추출해서 출력하는 표현식
✔ 저장 객체에서 값을 추출하는 순서
- page -> request -> session -> application (EL을 이용해 객체를 출력할 수 있다)
- 코드(jsp코드)
<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!-- ------------------------------- --> <!DOCTYPE html> <html lang="ko"> <head> <meta charset="UTF-8"> <title>spag</title> </head> <% pageContext.setAttribute("result", "hello"); %> <body> <%=request.getAttribute("result") %> 입니다. ${requestScope.result}<br> ${names[1]}<br> ${notice.title}<br> ${result}<br> ${empty param.n ? '값이 비어 있습니다' : param.n}<br> ${param.n/2 }<br> ${header.accept} </body> </html> - 코드 (자바코드 : 출력 코드)
package newlecture; import java.io.IOException; import java.util.HashMap; import java.util.Map; 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; @WebServlet("/spag") public class spag extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int num = 0; String num_ = request.getParameter("n"); if(num_ != null && !num_.equals("")) num = Integer.parseInt(num_); String result; if(num %2!=0) result = "홀수"; else result = "짝수"; request.setAttribute("result", result); String[] names = {"hyun","ddong"}; request.setAttribute("names",names); Map<String, Object> notice = new HashMap<String, Object>(); notice.put("id", 1); notice.put("title", "EL은 좋아요"); request.setAttribute("notice",notice); // redirect : 현재 작업한것과 상관없이 새로운 요청 // forward : 현재 작업한 내용을 이어갈 수 있도록 공유 RequestDispatcher dispatcher = request.getRequestDispatcher("spag.jsp"); dispatcher.forward(request, response); } }
▶ 출력 화면 