使用Servlet+JSP实现简单计算器功能,主要要求如下: Input.jsp:两个数据的输入及运算符的选择,并提交. Calculator.java:根据选择的运算符计算两个数的运算结果,并将结果转发到最终结果页面Result.jsp.使用RequestDispatcher对象实现转发. Result.jsp:显示最终结果. 请按顺序补全以下空格处代码: Input.jsp: + - * / Calculator.java: protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); float num1 = _______________3________________; float num2 =______________ _4________________; String op=_________________5________________; float num3=0; if(op.equals("1")) { num3=num1+num2; }else if(op.equals("2")) { num3=num1-num2; }else if(op.equals("3")) { num3=num1*num2; }else { _________________6_________________; } ServletContext context = _______7_______; RequestDispatcher rd = context._______8_______("/Result.jsp?result="_______9_______); rd._______10_______; }

Input.jsp:

<form action="Calculator" method="post">
  <input type="text" name="num1">
  <select name="op">
    <option value="1">+</option>
    <option value="2">-</option>
    <option value="3">*</option>
    <option value="4">/</option>
  </select>
  <input type="text" name="num2">
  <br>
  <input type="submit" value="Calculate">
</form>

Calculator.java:

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  request.setCharacterEncoding("utf-8");
  float num1 = Float.parseFloat(request.getParameter("num1"));
  float num2 = Float.parseFloat(request.getParameter("num2"));
  String op = request.getParameter("op");
  float num3 = 0;
  if(op.equals("1")) {
    num3 = num1 + num2;
  } else if(op.equals("2")) {
    num3 = num1 - num2;
  } else if(op.equals("3")) {
    num3 = num1 * num2;
  } else {
    if(num2 == 0) {
      response.sendRedirect("error.jsp");
      return;
    } else {
      num3 = num1 / num2;
    }
  }
  ServletContext context = getServletContext();
  RequestDispatcher rd = context.getRequestDispatcher("/Result.jsp?result=" + num3);
  rd.forward(request, response);
}

其中，空格处需要填写的代码如下：

1. `Float.parseFloat(request.getParameter("num1"))`
2. `Float.parseFloat(request.getParameter("num2"))`
3. `request.getParameter("num1")`
4. `request.getParameter("num2")`
5. `request.getParameter("op")`
6. `response.sendRedirect("error.jsp"); return;`
7. `getServletContext()`
8. `getRequestDispatcher`
9. `+ num3`
10. `forward(request, response)`