jsp中使用javabean实现简单运算 纠结ing 求大神！！！！

<html>

<body>

<form action="calculate.jsp" method="get">

第一个参数：<input type="text" name="first">

<br>操作运算符：

<select name="operator">

<option value="+">+</option>

<option value="-">-</option>

<option value="*">*</option>

<option value="/">/</option>

</select><br>

第二个参数：<input type="text" name="second">

<br><input type="submit" value="计算">

</form>

  </body>

</html>

<%@ page language="java" contentType="text/html" pageEncoding="UTF-8" import="java.sql.*"%>

<jsp:useBean id="calculator" scope="request" class=MyBean.SimpleCalculate">

<jsp:setProperty property="*" name="calculator"/>

</jsp:useBean>

<html>

<body>

<hr>

计算结果:<%

try{

calculator.calculate();

out.println(calculator.getfirst()+calculator.getoperator()+calculator.getsecond()+"="+calculator.getresult());

}

catch(Exception e)

{

out.println(e.getMessage());

}

%>

</body>

</html>