Java EE：从 POST 获取登录表单的参数

Java EE: Getting parameters from POST for a login form

提问by JF Beaulieu

I am trying to implement a simple login servlet but it's not working properly.

我正在尝试实现一个简单的登录 servlet，但它无法正常工作。

What I wanted to knowis how to pass the parameters using a HTTP POST. It already works with HTTP GET but the username and password are visible from the URL. It would be better to hide them in a POST.

我想知道的是如何使用 HTTP POST 传递参数。它已经适用于 HTTP GET，但用户名和密码可以从 URL 中看到。最好将它们隐藏在 POST 中。

<form method="post" action="home" >
  <input name="username" class="form-login" title="Username" value="" size="30" maxlength="2048" />
  <input name="password" type="password" class="form-login" title="Password" value="" size="30" maxlength="2048" />
  <input type="submit" value="Connect">
</form>

web.xml

网页.xml

  <servlet>
    <servlet-name>home</servlet-name>
    <servlet-class>controller.HomeController</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>home</servlet-name>
    <url-pattern>/home</url-pattern>
  </servlet-mapping>

Servlet:

服务端：

public class HomeController extends HttpServlet {

    private HttpSession session;
    private UserBean userBean;

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        UserBean user = new UserBean();
        String userName = request.getParameter("username");
        String password = request.getParameter("password");

        user.setUsername(userName);
        user.setPassword(password);

        user = UserDAO.login(user);

        dispatch(request, response, ApplicationRessource.getInstance().getHomePage());
    }

    protected void dispatch(HttpServletRequest request,
                HttpServletResponse response, String page)
            throws javax.servlet.ServletException, java.io.IOException {
        RequestDispatcher dispatcher = getServletContext()
                .getRequestDispatcher(page);
        dispatcher.forward(request, response);
    }
}

The problem is that the userNameand passwordstrings are always empty, meaning that the parameters are never fetched from the POST. What am I doing wrong?

问题是userName和password字符串始终为空，这意味着永远不会从 POST 中获取参数。我究竟做错了什么？

采纳答案by Subin Sebastian

it should work, can you check by changing form method to get and trying, you should see parameters in url.

它应该可以工作，您可以通过更改表单方法来检查并尝试，您应该在 url 中看到参数。

回答by Ankit

Please try this

请试试这个

In your doPost(..) method code only doGet(..) and put all your logic in doGet(..) and check if still it is giving blank values.

在您的 doPost(..) 方法中，仅代码 doGet(..) 并将所有逻辑放入 doGet(..) 并检查它是否仍然给出空白值。

Let me know what is the output.

让我知道输出是什么。

Example:-

例子：-

public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
           doGet(request,response);
}

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

        UserBean user = new UserBean();
        String userName = request.getParameter("username");
        String password = request.getParameter("password");

        user.setUsername(userName);
        user.setPassword(password);

        user = UserDAO.login(user);

        dispatch(request, response, ApplicationRessource.getInstance().getHomePage());
    } 

回答by Kshitij

this simple implementation should have worked ..but since its not, there maybe some code which is manipulating the request. The code you have posted is not sufficient to determine that.

这个简单的实现应该有效..但由于它没有，可能有一些代码正在操纵请求。您发布的代码不足以确定这一点。

Some pointers I can give are -

我可以给出的一些指示是——

1. Check your web.xmlto see if there is any filter/interceptor which is manipulating the request.

2. Which web/app server are you using? Have you checked the service(Http...)method implementation of HttpServlet. You can try placing a debug point in service(..) methodto see if the request object here has the required request parameters. If it doesn't, then the problem exists either in some filter or your jsp itself.

3. What does dispatch(request, response, ApplicationRessource.getInstance().getHomePage());do? I know the problem is before this line, but this is not a standard HttpServlet method, so I assume there's lot more custom code then whats been posted in the question above.

1. 检查您web.xml是否有任何过滤器/拦截器正在处理请求。

2. 您使用的是哪个网络/应用程序服务器？你检查过service(Http...)HttpServlet的方法实现了吗？可以try placing a debug point in service(..) method在这里查看请求对象是否有需要的请求参数。如果没有，那么问题要么存在于某个过滤器中，要么存在于您的 jsp 本身。

3. 有什么作用dispatch(request, response, ApplicationRessource.getInstance().getHomePage());？我知道问题在这一行之前，但这不是标准的 HttpServlet 方法，所以我假设有更多的自定义代码然后是上面问题中发布的内容。