If session exist or not
As far as I remember
session.getAttribute("xyz")
returns null if the attribute does not exist...
so your NullPointerException occurs because you try to call equals on null.
I suggest to do a check on your attribute itself before validating its content:
if (session.getAttribute("Username") == null || session.getAttribute("Username").equals(""))
Muaz Usmani
Updated on July 30, 2022Comments
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Muaz Usmani almost 2 years
I am trying to write my first app on
Google App Engine, I was trying to maintain a session, I created a login page on submit, it call to aservlet, servlet validates the user and create a new session using the following code.void createSession(String Username) { getThreadLocalRequest().getSession(true).setAttribute("Username", Username); }login page after calling the servlet redirects to some page i.e.
abc.jsp, myabc.jsppage contains<body><% try { if (request.getSession(false) == null) { } else { %> Welcome to <%=session.getAttribute("Username")%> <% if (session.getAttribute("Username").equals("")) { %> <a href="login.jsp"><b>Login </b></a> <% } else { %> <a href="logout.jsp"><b>Logout</b></a> <% } } } catch (Exception e) { } %></body>it works fine, but when I access
abc.jspwithout creating a session it is throwing an exception at thisif (session.getAttribute("Username").equals(""))line, I dunno why kindly help me. I think it dont detect if session exists. but I have read so many threads like this It gave me this solution, I dunno what I am doing wrong.