我有一個包含數據的表。我想添加一條新記錄。但是在某些時候，不可能考慮我引入的內容 控制臺 顯示 null。讀取數據生成空值帖子.jsp <h3 align="left">        <label id="name_form_genre">Добавить должность</label>    </h3>    id Должности:    <input type="text" id="post_id" style="width: 270px;" maxlength="15" value=""/>    Название:    <input type="text" id="post_name" style="width: 270px;" maxlength="15" value=""/>    <div align="left"> <button onclick="add_post()" id="button_form_post">Добавить</button></div>示例.js：function add_post() {var post_id = document.getElementById("post_id");var post_name = document.getElementById("post_name");if(post_id.value.toString().trim()=="" || post_name.value.toString().trim()==""){    alert("Поля не должны быть пустые!")}else {    var xhr = new XMLHttpRequest();    var body = 'action=add' + '&id=' + post_id.value + '&name=' + post_name.value;    xhr.open("POST", "post", false);    xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded; charset=utf-8");    xhr.send(body);    if (xhr.status != 200)        alert(xhr.status);    window.location = "/post";}}郵遞.java：@WebServlet("/post")public class PostServlet extends HttpServlet{private PostService postService = new PostService();public PostServlet() throws SQLException, ClassNotFoundException { }protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    processRequest(request, response);}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    request.getRequestDispatcher("post.jsp").forward(request, response);}有人可以幫助確定問題嗎？提前致謝。