将表单单选项值发送到Java servlet，返回null

<form action="servlet-url" method="POST">
  <!-- 单选项 -->
  <input type="radio" name="option" value="value1"> Option 1
  <input type="radio" name="option" value="value2"> Option 2
  <!-- 其他表单元素 -->
  <!-- ... -->
  <input type="submit" value="Submit">
</form>

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  String optionValue = request.getParameter("option");
  // 处理选中的值
  // ...
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  String optionValue = request.getParameter("option");
  // 处理选中的值
  // ...
  
  // 返回null
  response.getWriter().write("null");
}