hi every one

i am little bit confused with seam conversaction,
this is my samble code,

@Stateful
@Name("productsearch")
public class ProductListAction  implements Serializable,ProductsList
{

@In(required=false)
@Out(required=false)
Product selectedProduct;

@RequestParameter
Long rowIndex;

@RequestParameter
Long category;

@Out(required=false)
List<Product> productsList;

@Begin(join=true)
public String search()
{
   productsList=em.createQuery("from products p where p.category=:category")
                .setParameter("category",category)
                .getResultList;
   return "/productSearch.xhtml;"
}

public String select()
{
   selectedProduct=productsList.get(rowIndex);
   return "/productSpec.xhtml";
}
@End
public String cancel()
{
   return "/home.xhrml";
}
}

my entity Product also in default scope,
i did not use any scope type.

i am getting the null pointer exception from select method,
while select the product from the list.

because , the list is empty, what is the worng with my code.

i am expect the productsList should be live untill if i am invoke the cancal method.

do i need to cahnge the scope type of the productsList to avoid the null pointer exception.
i need to know which object should be live in between begin and end method invokation.
either productsearch or productsList.