Bug 257026

"Persistence - JSF Pages from Entity Classes" generates code that issues multiple "SELECT COUNT(.." queries for every page view.  For example, when navigating to the "List" view the "SELCT COUNT(.." query is executed 9 times.  This is incredibly inefficient and makes the UI very sluggish.

One way to remedy this would be to cache the row count in the Abstract Facade, although, there may be better solutions.  When this is the done the UI is 5 to times faster.  Here is an example of how the AbstractFacade could be improved:

public abstract class AbstractFacade<T> {

    private Class<T> entityClass;
    private int cachedCount = -1;

    public AbstractFacade(Class<T> entityClass) {
        this.entityClass = entityClass;
    }

    protected abstract EntityManager getEntityManager();

    public void create(T entity) {
        getEntityManager().persist(entity);
        cachedCount=-1;
    }

    public void edit(T entity) {
        getEntityManager().merge(entity);
    }

    public void remove(T entity) {
        getEntityManager().remove(getEntityManager().merge(entity));
        cachedCount=-1;
    }

    public T find(Object id) {
        return getEntityManager().find(entityClass, id);
    }

    public List<T> findAll() {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        return getEntityManager().createQuery(cq).getResultList();
    }

    public List<T> findRange(int[] range) {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        javax.persistence.Query q = getEntityManager().createQuery(cq);
        q.setMaxResults(range[1] - range[0] + 1);
        q.setFirstResult(range[0]);
        return q.getResultList();
    }

    public int count() {
        if (cachedCount == -1) {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        javax.persistence.criteria.Root<T> rt = cq.from(entityClass);
        cq.select(getEntityManager().getCriteriaBuilder().count(rt));
        javax.persistence.Query q = getEntityManager().createQuery(cq);
        cachedCount = ((Long) q.getSingleResult()).intValue();
        }
        return cachedCount;
    }