Question

You have the EntityManager.find(Class entityClass, Object primaryKey) method to find a specific row with a primary key.

But how do I find a value in a column that just have unique values and is not a primary key?

Answer 1

For example, like this:

List<T> results = em.createQuery("SELECT t FROM TABLE t", T.class)
                        .getResultList();

With parameters:

List<T> results = em.createQuery("SELECT t FROM TABLE t where t.value = :value1")
                        .setParameter("value1", "some value").getResultList();

For single result replace getResultList() with getSingleResult():

T entity = em.createQuery("SELECT t FROM TABLE t where t.uniqueKey = :value1")
                 .setParameter("value1", "KEY1").getSingleResult();

One other way is to use Criteria API.