asked on

null pointer exception on HttpServletRequest

hi experts ,

I have a java file and i have a method in it.
it goes like this

public class xyz
{
ArrayList jurisdictionIds = getJuriIds();
public ArrayList getJuriIds()
{
String[] juriIds = new String[1000];

HttpServletRequest request= null;
request=(HttpServletRequest)request.getSession();
HttpSession session= request.getSession();
System.out.println("CHECKER++++");

UserVO usrvo = (UserVO)session.getAttribute("userDetails");
String groupId= usrvo.getGroupId();
call DAO and get collection;

return arraylist;
}

}

The problem is I am creating a session object above, but its throwing a null pointer exception when this method is called.

I am assuming its because i am giving HttpServletRequest request= null;

any ideas how i can correct this problem.
I cannot do HttpServletRequest req= new HttpServletRequest (); because it says HttpServletRequest cannot be instantiated.

any help greatly appreciated,
thanks
J

SOLUTION

Mick Barry

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Mick Barry

if u need the request then it should be passed as a parameter:

public ArrayList getJuriIds(HttpServletRequest request)
{
HttpSession session= request.getSession();
System.out.println("CHECKER++++");

UserVO usrvo = (UserVO)session.getAttribute("userDetails");
String groupId= usrvo.getGroupId();
call DAO and get collection;

return arraylist;
}

Manikandan Thiagarajan

ArrayList jurisdictionIds = getJuriIds(req);

pass that request object here as per object told

jaggernat

ASKER

>>>>what is it u are trying to do?

just trying to create a session in java class because i want to get the object 'userDetails' (session.getAttribute("userDetails");
which is in session.

Mick Barry

then pass the request (or the session) as a parameter

wcleung9

Except the nature of HttpServletRequest and HttpSession classes, I would like to point out some coding error:

First you set the request pointer to be null:
HttpServletRequest request= null;

Then you call its method getSession():
request=(HttpServletRequest)request.getSession();

This will definitely induce a NullPointerException! The request pointer is not pointing to any object. You just set it to null yourselves.

And, even if the request pointer is pointing to a object, this line of code will induce a ClassCastException. Calling request.getSession() will return a HttpSession object. You can't cast it to a HttpServletRequest object. In Java, you can only cast an object to its parent class, or the interface it implements.

wcleung9

>In Java, you can only cast an object to its parent class, or the interface it implements.

Sorry, it should be:
you can only cast an object to its sub class

jaggernat

ASKER

when i do something like this its giving me error

ArrayList jurisdictionIds = getJuriIds(HttpServletRequest request);
public ArrayList getJuriIds(request)

{
HttpSession session= request.getSession();
System.out.println("CHECKER++++");

UserVO usrvo = (UserVO)session.getAttribute("userDetails");
String groupId= usrvo.getGroupId();
call DAO and get collection;

return arraylist;
}

ASKER CERTIFIED SOLUTION

Mayank S

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Leo Eikelman

From what context are you calling this method?

Because the problem is in this line

>>request=(HttpServletRequest)request.getSession();

returning null, which might mean you are calling it from the wrong context because it can not find a session

Leo

Mayank S

Its been corrected in the later code which was posted by jaggernat. Just a compilation error issue which I guess is fixed?

jaggernat

ASKER

thanks.works