> Yea, I can see how that would work. You're just saying to put
> the "black box" in the ListView, right?
There is no black box. The paging that the pagedlist does is no longer
necessary.
> Your DataProvider
> interface is a bit too simple (doesn't allow ordering, and
> EJB and Hibernate2 can't wrap an object in a model with only
> the object itself for reference), but I think it could work
> nicely with some fleshing out.
I am working on example that does both of the above, here are some snippets:
Sorting (I know its not generalized yet, just a working prototype)
public class SortableContactDataProvider extends ContactDataProvider
{
private String sort; // <===== yes later this will be a list of
sortparams
public Iterator iterator(int first, int count)
{
return getContactsDB().find(first, count, sort).iterator();
}
public void setSort(String sort) {
this.sort=sort;
}
public String getSort() {
return sort;
}
}
Model wrapping:
public class DetachableContactModel extends AbstractReadOnlyDetachableModel
{
private long id;
private transient Contact contact;
protected ContactsDatabase getContactsDB() {
return DatabaseLocator.getDatabase();
}
public DetachableContactModel(Contact c) {
this(c.getId()); // <=========== here is the trick
contact=c;
}
public DetachableContactModel(long id) {
if (id==0) throw new IllegalArgumentException();
this.id=id;
}
protected void onAttach()
{
if (contact==null) { // <======== no need to load if ctor
with object used
contact=getContactsDB().get(id);
}
}
...
}
> Returning an Iterator is very nice. If all you need to do is
> iterate, there's no reason to require a List.
What more can you do with a read-only list?
> But because I'm
> implementing a List, there's no way to incorporate that.
> However, returning a list WILL use the cache, just not by
> default. You have to set useQueryCache to true.
I don't think that works the same way, I might be wrong though. If you set
hibernate.use_query_cache=true and then set query.setCachable(true) you will
cache the entire resultset which is not the same. When you call
query.iterate() it uses n+1 queries to retrieve data, that means the first
query gets all the primary keys, and then it retrieves the objects object by
object (the other n queries) so you end up with each object being cached
separately in the cache not as the entire resultset. This gives you a much
higher cache-hit chance when retrieving multiple objects and when retrieving
an object by pk.
-Igor
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