Logout Help

feylya

Hopefully someone can help me with this. Kinda Urgent.

My problem is I'm using Java Servlet's to log into a webpage, getting the information for login from a database. The code for logging in is:

LoginBean loginBean = (LoginBean) request.getAttribute("loginBean") ;

HttpSession session = request.getSession(true) ; // creates if does not already exist
String state = (String) session.getAttribute("state") ;

It then searches the database, looking for the login information. If it finds it:

session.setAttribute("member", member) ;
session.setAttribute("state", "Registered") ;
request.setAttribute("message", WELCOME_MEMBER + member.getFirstName() ) ;
page = messagePage ;

That all works perfectly. The problem comes when I try to log out and log back in:

request.setAttribute("memberBean", null);
request.setAttribute("loginBean", null);
request.setAttribute("state", null);
HttpSession session = request.getSession() ;
session.invalidate();
		
session = request.getSession(true);

When I click to log back on, I get this error message:

java.lang.NullPointerException
	at cp3036proj.command.LoginCommand.execute(LoginCommand.java:30)
	at cp3036proj.servlets.FrontController.doGet(FrontController.java:70)

I'm using TomCat. This has completely stumped me. I'd really appreciate any help cos I'm in a rush to get this working

deadl0ck

What's the actual line that's causing the error ?

Put System.out.println("Here 1"); etc. in the code, if the line number (30) doesn't correlate to an actual line of code.

Also - if this line calls a method,what's the method signature ?

feylya

Line 30 seems to be:

if (state.equals("Registered") )

SoP won't work cos I don't have any way of testing this due to the jsp. In other words, I don't know how to :P

This is using a front controller and when I go back to the controller address (/cp3036projapp/controller) instead of a page (/cp3036projapp/controller?command=Login) and then go to the Login page, it works.

deadl0ck

state has been set to null with the line :

request.setAttribute("state", null);

Then you're trying to compare a null string to "Registered" - that's the error

Use :

if (state != null && (state.equals("Registered") ))
{
// Do your stuff
}

feylya

I tried changing it to request.setAttribute("state", ""); and that didn't work. I'll try your way now.

I just made a work around, where after you log out, the only link available is a link back to the controller so the entire session is reset. Not ideal but it'll do if I can't solve this other ways.

feylya

Cheers deadl0ck, worked perfectly.

BTW, request.removeAttribute("") works best

deadl0ck

No problemo

NotMe

feylya wrote:

SoP won't work cos I don't have any way of testing this due to the jsp. In other words, I don't know how to :P

By the way, System.out.println() outputs to a log file in Tomcat/logs. Very handy for debugging.

feylya

I did not know that!