Question

Using an EntityManager in an abstract class, I am trying to create a function that returns a list of all the results in a table from the entity class. Each table has its own persistence class that inherits from the abstract class. So far I have:

public abstract class AbstractFacade<T> {
    private Class<T> entityClass;

    ...

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

That works for JPA 2.0 but I just discovered that my server is restricted to JPA 1.0 which doesn’t support getCriteriaBuilder() or createQuery(CriteriaQuery cq)

Is there a way I can re-factor my code to do relatively the same thing with a mechanism that exists in JPA 1.0?

Answer 1

You can use the following approach:

public List<T> findAll() {
    return (List<T>) getEntityManager().createQuery(
        "select e from " + entityClass.getSimpleName() + " e")
        .getResultList();
}

Note that it won’t work if you override logical entity names (@Entity(name = ...)), but it’s not a common case in practice.