java session().getAttribute 返回 null
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session().getAttribute is returning null
提问by user1407668
I have a servlet which calls a jsp page. In the servlet I am retrieving the username provided at the login correctly. But after setting the same in session, when i access the called jsp page, its returning null.
我有一个调用jsp 页面的servlet。在 servlet 中，我正在正确检索登录时提供的用户名。但是在会话中设置相同后，当我访问被调用的jsp页面时，它返回null。
Servlet Code:
服务程序代码：
public class AdminServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = -4244742541587179390L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String userName = request.getParameter("name");
System.out.println("UserName: " + userName); // Here it prints the username properly
request.getSession(true).setAttribute(request.getParameter("name"), userName );
RequestDispatcher rd = request.getRequestDispatcher("upload.jsp");
rd.forward(request, response);
// response.sendRedirect("upload.jsp");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}
}
JSP Code snippet where I am accessing this:
我正在访问的 JSP 代码片段：
<label class="message">Welcome <%= session.getAttribute("userName") %></label>
What am I doing wrong here? Can anyone help please
我在这里做错了什么？任何人都可以帮忙吗
采纳答案by Verdi
I think you inverted the two params. It should be like this:
我认为你颠倒了两个参数。应该是这样的：
request.getSession(true).setAttribute("userName", userName );
回答by Nimesh
you should get session value from the value of
您应该从以下值中获取会话值
request.getParameter("name");
or in servlet you need as follow:
或者在 servlet 中你需要如下：
request.getSession(true).setAttribute("userName",request.getParameter("name") );
request.getSession(true).setAttribute("userName",request.getParameter("name"));
回答by Stefan Beike
this is wrong:
这是错误的：
request.getSession(true).setAttribute(request.getParameter("name"), userName );
I think it should be
我认为应该是
request.getSession(true).setAttribute("userName", userName );
回答by Verdi
Just had a quick look I think this might be a little similar and might help: JSP Session.getAttribute() value return null
快速浏览一下，我认为这可能有点相似，可能会有所帮助：JSP Session.getAttribute() value return null
