getParamteter在对java servlet的ajax调用中不能处理文本元素

Question

嗨，我有一个名字和pw文本字段与提交按钮。问题是，无论我输入什么值，servlet都不会接收到。我不知道问题是JQUERY试图获取HTML元素值，还是servlet无法从ajax调用中获取值。

<section id="customer_business">
        <div class="container">
            <div class="row">
                <div class="col-sm-6 col-xs-12 customer">
                    <div class="hover ehover3">
                        <img class="img-responsive" src="images/p13.jpg" 
    alt="">
                        <div class="overlay">
                            <div class="row">
                                <div class="col-sm-6 col-xs-12">
                                    <div class="form-group"> 
                                        <input type="text" id="cus_name" 
   class="form-control" maxlength="10" placeholder="Full Name" required>
                                    </div>
                                </div>
                                <div class="col-sm-6 col-xs-12">
                                    <div class="form-group"> 
                                        <input id="cus_password" 
    type="password" class="form-control" maxlength="22" 
    placeholder="Password" required>
                                    </div>
                                </div>
                            </div>

                            <div class="col-sm-2 col-xs-12">

                            </div>

                            <div class="col-sm-8 col-xs-12">
                                <div class="col-sm-6 col-xs-6">
                                    <a href="custreg.html"><button 
    id="cus_register" class="info" type="button">Register</button></a>
                                </div>
                                <div class="col-sm-6 col-xs-6">
                                    <a href="#"><button id="cus_login" 
class="info" type="button">Login</button></a>



                                </div>

$('#cus_login').click(function() {
    $.ajax({
        url: 'LoginServlet',
        type: 'POST',
        contentType: 'application/json',
        dataType: 'json',
        data: JSON.stringify({
            username : $("#cus_name").text(), 
            pw : $("#cus_password").text(), 
            method : "customer"
        }),
        success: function(result) {
            var obj = result;
            if(result.status == true) {
                alert("Success!");
            }
            else{
                alert("Login failure, please check and try again");
            }
        }
    });
});

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    System.out.println("Servlet reached successfully");

    RequestDispatcher custdispatch = 
 request.getRequestDispatcher("CustProfile.html");
    RequestDispatcher busdispatch = 
 request.getRequestDispatcher("BusEntry.html");

    boolean isValid = false;
    String method = request.getParameter("method");
    String username = request.getParameter("username");
    String pw = request.getParameter("pw");
    System.out.println(method + username + pw);

我一直得到3个空值。这一定是ajax和servlet之间的问题。如果查看method属性，它不是从用户输入或任何html元素中获取的，而是硬编码的，但在servlet中返回null。

Answer 1

答：getVal（）确实是正确的选项。问题不是js从HTML中提取。问题是servlet没有从ajax POST中获取数据。原因是因为数据被设置为json，但是servlet不能读取json格式，所以下面的代码：

JsonObject data = new Gson().fromJson(request.getReader(), JsonObject.class);
    String method = data.get("method").getAsString();
    String username = data.get("username").getAsString();
    String pw = data.get("pw").getAsString();

数据变量是将json ajax post参数转换为java对象。