In Hibernate, couldn't you just use get(Class entityClass,
Serializable id) rather than doing the whole uniqueResult() stuff?
On Thu, Apr 17, 2008 at 9:09 AM, Nino Saturnino Martinez Vazquez Wael
<[EMAIL PROTECTED]> wrote:
> Using jpa you can do it this way:
>
> private BaseEntity findById(String table, Long id) {
> Query query = entityManager.createQuery("select p from " + table
> + " p where p.id=" + id);
> return (BaseEntity) query.getSingleResult();
>
> }
>
> private List findBaseEntity(int first, int count, String property,
> boolean ascending, String table) {
> Query query = entityManager.createQuery("select p from " + table
> + " p order by p.:property :sort");
> query.setParameter("property", property);
> if (ascending) {
> query.setParameter("sort", "asc");
> } else {
> query.setParameter("sort", "desc");
> }
> query.setFirstResult(first);
> query.setMaxResults(count);
> return (List<BaseEntity>) query.getResultList();
> }
>
> and this in hibernate:
>
> public Promo findPromo(Long id) {
> Criteria criteria =
> getHibernateSession().createCriteria(Promo.class);
> criteria.add(Restrictions.eq("id", id));
> return (Promo) criteria.uniqueResult();
> }
>
> public List<Promo> findPromo(int first, int count, String property,
> boolean ascending, Company company) {
> Criteria criteria = getHibernateSession().createCriteria(Promo.class)
> .add(Restrictions.eq("company", company));
> criteria.setMaxResults(count);
> criteria.setFirstResult(first);
> if (ascending) {
>
> criteria.addOrder(Order.asc(property));
> } else {
> criteria.addOrder(Order.desc(property));
> }
> return (List<Promo>) criteria.list();
> }
>
> public int promoCount(Company company) {
> Criteria criteria = getHibernateSession().createCriteria(Promo.class)
> .add(Restrictions.eq("company", company));
> criteria.setProjection(Projections.rowCount());
> Object obj = criteria.uniqueResult();
> return (Integer) obj;
> }
>
> gumnaam23 wrote:
>
> > I have done this, and it works quite nicely.
> >
> > Be warned though, the biggest bottle neck in this, is the loading of the
> > data from database.
> > So for best performance, you should read only one page's worth data at a
> > time from your DB
> > (in your case 500).
> >
> > If you load the whole data, and use some thing like a list iterator, you
> > will not get any performance
> > benefit.
> >
> > Unfortunately ANSI SQL has no syntax for pagination of results. So you
> have
> > 2 choices.
> >
> > 1) Keep an open DB cursor , and retrieve as much data as you want per page
> > rendering. But this
> > ties your cursor to the user session. Not a very good idea.
> >
> > 2) Use the vendor specific way to get paginated results. Almost all major
> > vendors support pagination
> > of query results in their own idiosyncratic way.
> >
> > If you go with approach 2, you can even use the
> > AjaxFallbackDefaultDataTable, which will do all the
> > pagination etc for you, and with AJAX to boost.
> > You only need to provide a SortableDataProvider, which implements the
> size()
> > and iterate(int lower, int upper) calls. Your size() call should fetch a
> total count of items. i.e. select count(*) and the iterate(int lower, int
> upper) should retrieve the query results
> > between lower and upper limit.
> > And with sortable data provider, you even get sorting for free. (I mean
> the
> > UI, you do have to write
> > the back end implementation your self).
> >
> > For my case, I use iBatis for DB access, so it is really easy to write DB
> > Vendor specific queries and
> > yet retain the pagination abstraction. If I need to work with another DB ,
> I
> > can easily swap the
> > pagination query part.
> >
> > Hope this has helped.
> >
> >
> >
> > PhilipJohnson wrote:
> >
> >
> > > * Finally, when I am displaying Page 1 containing 500 rows (using
> > > something like PageableListView), I'd like to only populate my model
> with rows 1-500 from
> > > my backing store. Let's say the user then clicks on Page 3: at that
> point, I'd like
> > > to go retrieve rows 1001-1500 from my backing store and populate my
> model for rows
> > > 1001-1500. How would one go about doing this? Would it be possible to
> kind of sketch out the
> > > approach for me?
> > >
> > >
> > >
> >
> >
> >
>
> --
> -Wicket for love
>
> Nino Martinez Wael
> Java Specialist @ Jayway DK
> http://www.jayway.dk
> +45 2936 7684
>
>
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