Technically it's fine, but conceptually I'm not sure about passing a
command object to a pager. What does it mean to page a command?
Another option would be to get rid of the Pager altogether. The only
state held in the Pager if you get rid of the Command is the page size
and current index. We could easily stash those on the root DataObject
(even in the static case we will have a containing DataObject created
by the DAS.) Then you could move nextPage(), previousPage(), and
getPage() to Command.
Brent
On 11/8/06, Kevin Williams <[EMAIL PROTECTED]> wrote:
The RDB DAS currently has a simple paging capability that is implemented
by wrapping a Command. Here is a simple example:
// Build command to read all customers
Command readCustomers = das.createCommand("select * from
CUSTOMER order by ID");
// Create a pager with page size 15
Pager pager = new PagerImpl(custCommand, 15);
// Get and work with first page
DataObject root = pager.next();
// Get and work with the second page
root = pager.next();
// First page again
root = pager.previous();
This works well if the client of the page data is on the server but not
so well if the client is not. The reason is that the pager wraps a
command instance which, in turn, references a connection. For a pager
to work in a "disconnected" mode it should probably be serializable and
very lightweight (it might be stored in session for instance) and it
cannot count on the original connection to be available. I think this
could easily be achieved by removing the instance variable from the
pager that references it's command. Instead, the command can be passed
as an argument to the paging methods like this:
DataObject root = pager.next(someReadCommand);
Does this sound reasonable?
--
Kevin
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