求救啊 大神们，点击button 删除按钮没任何反应，传不到servlet去

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title><script type="text/javascript">
function del(id){
   var flag=confirm("确认删除吗");
        if(flag){
           document.form1.action="User_Servlet?flag=del&id="+id;
          document.form1.submit();
        }
}
</script>
</head><body>
<form id="form1" name="form1" method="post" action="${pageContext.request.contextPath}/User_Servlet"><input type="button" name="button" id="button" value="删除"  onclick="del('${user.id}')"  class="input-button" >
</body>
</html>光看方法的话貌似没问题阿