NullPointerException

[krishna prasad gunasekaran]

when i call a remote method on ejb, it throws a NullPointerException.
i am passing a VO as an argument.

code:
in Action

somewhere in my Action code...
ArrayList al = (ArrayList) EJBRemote.xyz(VO);

in Remote Interface
public collection EJBRemote.xyz(VO) throws RemoteException;

in Session Bean
public collection EJBRemote.xyz(VO){
Dao.getXYZ(VO);
}

Error code :
java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.ServerException: RuntimeException; nested exception is:
java.lang.NullPointerException

I have checked the code in DAO, there is no way it is going to throw NullPointerException. what could be the reason for NullPointerException?

[Dilip Viswanath]

is your VO serializable?

[Jeanne Boyarsky]

Krisp,
Let's start by trying to narrow down the problem. Does it work if you comment out the call to the DAO? If not, we can rule out the DAO. Does it work if you pass null as the VO? If not, the problem is in the VO.

[krishna prasad gunasekaran]

Jeanne, i did not comment out the call to DAO, instead i used the codes in DAO in my Action. It worked perfectly. when i passed null, instead of VO, no exception was thrown out. the code exection was back on track. so can we rule out the parts of DAO and VO.

what could be the reason