大家帮下!!

<%@ page language="java" contentType="text/html;charset=UTF-8"%>
<html>
<head>
<title>代码段新增</title>
<meta http-equiv="content-type" content="text/html;charset=UTF-8" />
<script type="text/javascript">
function submit_form(){
  document.form1.submit();
}
</script>
<link href="css/code.css" type="text/css" rel="stylesheet" />
</head>
<body>
        <%
                String check1="";
if (request.getParameter("radio_add").equals("add_school")) 
                   check1="checked";
                else
                   check1=""; %>
<form action="add_form.jsp" method="post" name="form1">
<div id="top">
<input type="radio" name="radio_add" value="add_school" <%=check1%>
style="margin-left:2px;" onclick="submit_form();" />
<span id="span1">学校信息</span>
<input type="radio" name="radio_add" value="add_time"
style="margin-left:17px;" onclick="submit_form();" />
<span class="span2">时间段</span>
<input type="radio" name="radio_add" value="add_classno"
style="margin-left:11px;" onclick="submit_form();" />
<span class="span2">班 级</span>
<input type="radio" name="radio_add" value="add_course"
style="margin-left:8px;" onclick="submit_form();" />
<span id="span3">课程名</span>
<input type="radio" name="radio_add" value="add_testtype"
style="margin-left:9px;" onclick="submit_form();" />
<span class="span2">考试类型</span>
</div>
</form>
<div id="center">
<span>请选择所需要的类型!</span>
</div>
<div id="bottom">
<span><a href="#" onclick="javascript:window.close();">关闭窗口</a>
</span>
</div>
</body>
</html>关于上面红色所标志的"check",如何才能实现?
老是报NullPointerException的错误

解决方案 »

  1.   

    可以用javascript实现。
    <script language = "javascript">
        <%
           if (request.getParameter("radio_add").equals("add_school"))  
         %>
         document.all.radio_add.checked='true';
    </script>
      

  2.   

    request.getParameter("radio_add") 可能是这个没拿到吧 request为null所以才报这个错改成这样看看：if ("add_school".equals(request.getParameter("radio_add")))
      

  3.   

          <% 
                    String check1=""; 
    if(request.getParameter("radio_add")!=null){
    if (request.getParameter("radio_add").equals("add_school"))  
                       check1="checked"; 
                    else 
                       check1="";
    }
     %> 
      

  4.   

    request.getParameter("radio_add")这个取出来的是null,所以调用String的equals方法的时候抛出这异常