<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
function nn() {
const n = frmsum.nvalue.value;
if(n=='' || n==0){
alert('0보다 큰값을 입력해 주세요!');
frmsum.nvalue.focus();
}else{
frmsum.submit();
}
}
</script>
</head>
<body>
<h2>n까지의 합계 구하기</h2>
<form name="frmsum" action="/jsp01/ex02/20210526_01_forward.jsp">
n값은? <input type="number" name="nvalue" required="required">
<button type="button" onclick="nn()">확인</button>
</form>
<div>
<span>결과</span> <br>
<%
int sum = 0;
if(request.getAttribute("sum")!=null){
sum = (int)request.getAttribute("sum");
}
%>
합계는 <%=sum%>
</div>
</body>
</html>