使用Jsp的单选按钮值为空

Question

    <form action="add.jsp" method="POST">
    <table cellpadding ="10" cellspacing="10">
        <tr>
            <td> <input type="radio"  name="r1" id="add"  > +</td>   
        </tr>
         <tr>
        <td> <input type="radio"  name="r1" id="min" > -</td>

        </tr>
         <tr>
        <td> <input type="radio" name="r1" id="sub"  > *</td>
        </tr>
         <tr>
        <td> <input type="radio" name="r1" id="div" value="div" > %</td>
        </tr>
         <tr>
          <td> Num1 </td>   
          <td> <input type="text" name="num1" id="num1" > </td>
        </tr>
         <tr>
        <td> Num2 </td>   
        <td> <input type="text" name="num2" id="num2" > </td>
        </tr>


           <tr>

        <td> <input type="submit" value="Ok" > </td>
        </tr>
    </table>
 </form>   

<%

        String str = request.getParameter("r1");
        String str1 = request.getParameter("r1"); 
        String str2 = request.getParameter("r1");
        String str3 = request.getParameter("r1");


String final_output="";

   int num1;
   int num2;
   int tot=0;

     num1 = Integer.parseInt(request.getParameter("num1"));
     num2 = Integer.parseInt(request.getParameter("num2"));

        if(str.equals("add"))
        {
            tot = num1 + num2;
        }
        else if(str1.equals("min"))
        {
            tot = num1 - num2;
        }
        else if(str2.equals("sub"))
        {
            tot = num1 * num2;
        }
        else if(str3.equals("div"))
        {
            tot = num1 / num2;
        }

        Integer result = new  Integer(tot);
        out.println(result.toString()); 

%>

我更改为r1，但值是否可以

Answer 1

更改单选按钮，将value放入其中，如下所示：

<input type="radio"  name="r1" id="add" value="add" >

按以下方式处理值：

String str = request.getParameter("r1");
if ("add".equals(str)) {
   ...
} else if("sub".equals(str)){
   ...
}

删除以下所有行：

String str1 = request.getParameter("r1"); 
String str2 = request.getParameter("r1");
String str3 = request.getParameter("r1");