Question

我正在使用多个文件和servlet，并以下列方式将变量作为标志传递：

managerPage.jsp：

<fieldset>
  <legend>To open a new account</legend> 
  <form action="employeeTransaction1">    
      <input type="hidden" name="hdField" value="managerFlagOn" />
      <input type="submit" value="Press here to continue" />
  </form>
</fieldset>

现在我转到 employeeTransaction1 servlet：

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
{


    HttpSession session = request.getSession();
    synchronized(session) 
    {
        String hiddenValue = request.getParameter("hdField");

        // then the redirection was made from a Manager's page
        if (hiddenValue.equals("managerFlagOn") == true) 
        {
            session.setAttribute("managerQuery1", hiddenValue);
        }
        // forwards to the page employeeOpenNewAccount.jsp
        request.getRequestDispatcher("/WEB-INF/results/employeeOpenNewAccount.jsp").forward(request, response);
    }

}

在这里，我抓住隐藏的值并将其放在名称managerQuery1下。

然后我被转发到employeeOpenNewAccount.jsp：

employeeOpenNewAccount.jsp：

<!-- EMPLOYEE OP 1 -  open a new account -->


<!DOCTYPE html>
<html>
<head><title>Employee's transaction page - open a new account</title>
<link rel="stylesheet"
      href="./css/styles.css"
      type="text/css"/>
</head>
<body>


<h1>Employee's transaction page!</h1>
<h1>
Open a new Bank account
</h1>

<!-- from here redirecting to the servelet that's called "employeeOperation1" -->

<fieldset>
  <legend>Please fill the followings</legend>
  <form action="employeeOperation1"> 
    First-name : <input type="text" name="firstName"><br>
    Last-name : <input type="text" name="lastName"><br>
    Address : <input type="text" name="address"><br>
    ID-number : <input type="text" name="idNumber"><br>
    User-name : <input type="text" name="userName"><br>
    Password : <input type="text" name="password"><br>
    <input type="submit" value="Register">
  </form>
</fieldset>

</body></html>

现在我转到employeeOperation1 servlet：

employeeOperation1：

@WebServlet("/employeeOperation1")
public class EmployeeServlet1 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    HttpSession session = request.getSession();
    synchronized(session) 
    {

       String manager = request.getParameter("managerQuery1");   // the value is null
        ...
        ...
    }
}

现在抓取manager后managerQuery1的值为null。

为什么它为空？我认为会话变量应该一直持续到程序结束。

谢谢

Answer 1

您在manager属性中设置managerQuery1，并尝试从请求参数中获取它。

从会话中获取它，你就完成了。

String manager = session.getAttribute("managerQuery1");

Answer 2

String manager = session.getAttribute("managerQuery1");

我认为你需要加入String

String manager =(String) session.getAttribute("managerQuery1");

您可以关注以获得更多想法。

  javax.servlet.http.HttpSession session = request.getSession();

完成后，您可以设置如下会话对象： session.setAttribute（ “姓名”， “值”）;

要检索该值，请执行以下操作：

    String foo = (String) session.getAttribute("name");

Session无法从以前的会话中找到变量

2 个答案: