JPA Criteria API by samples — Part-I

Although examples are pretty much simple it will help you with finalized version of JPA 2.0 API.

For Part II please read JPA Criteria API by samples — Part-II

and in this examples in my opinion building query by programming is not so easy and maintainable but still possible.

PS: I tested it with hibernate 3.5.1

Simple Query

Query query = entityManager.createQuery("from SimpleBean s");
List<SimpleBean> list = query.getResultList();
CriteriaBuilder criteriaBuilder =entityManager.getCriteriaBuilder();
CriteriaQuery<Object> criteriaQuery = criteriaBuilder.createQuery();
Root<SimpleBean> from = criteriaQuery.from(SimpleBean.class);
CriteriaQuery<Object> select = criteriaQuery.select(from);
TypedQuery<Object> typedQuery = entityManager.createQuery(select);
List<Object> resultList = typedQuery.getResultList();
assertEqualsList(list, resultList);

Simple Query with Order

List<SimpleBean> expected= entityManager.createQuery("from SimpleBean s order by s.pbyte asc ,s.pint desc").getResultList();
//...
CriteriaQuery<Object> select = criteriaQuery.select(from);
select.orderBy(criteriaBuilder.asc(from.get("pbyte")),criteriaBuilder.desc(from.get("pint")));
TypedQuery<Object> typedQuery = entityManager.createQuery(select);
//...

Simple Query with selected fields

Query query = entityManager.createQuery("select s.id,s.pbyte from SimpleBean s ");
List listExpected = query.getResultList();
//...
CriteriaQuery<Object> select = criteriaQuery.multiselect(from.get("id"),from.get("pbyte"));

Query with single criteria

int arg1 = 20000;
Query query = entityManager.createQuery("from SimpleBean s where s.pint>=:arg1");
query.setParameter("arg1", arg1);
List<SimpleBean> list = query.getResultList();
//...
CriteriaQuery<Object> select = criteriaQuery.select(from);Predicate predicate = criteriaBuilder.ge(from.get("pint"), arg1);
criteriaQuery.where(predicate);
//...

Query with multiple criterias

int arg1 = 20000;
int arg2 = 50000;
Query query = entityManager.createQuery("from SimpleBean s where s.pint>=:arg1 and s.pint<=:arg2");
query.setParameter("arg1", arg1);
query.setParameter("arg2", arg2);
List<SimpleBean> list = query.getResultList();
//..
Predicate predicate1 = criteriaBuilder.ge(from.get("pint"), arg1);
Predicate predicate2 = criteriaBuilder.le(from.get("pint"), arg2);
criteriaQuery.where(criteriaBuilder.and(predicate1, predicate2));
//..

Query with single literal

String arg1 = "name";
Query query = entityManager.createQuery("from SimpleBean s where upper(s.pstring) like upper(:arg1)");
query.setParameter("arg1", arg1);
List<SimpleBean> list = query.getResultList();
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Object> criteriaQuery = criteriaBuilder.createQuery();
Root from = criteriaQuery.from(SimpleBean.class);
CriteriaQuery<Object> select = criteriaQuery.select(from);
Expression<String> literal = criteriaBuilder.upper(criteriaBuilder.literal((String) arg1));
Predicate predicate = criteriaBuilder.like(criteriaBuilder.upper(from.get("pstring")), literal);
criteriaQuery.where(predicate);
TypedQuery<Object> typedQuery = entityManager.createQuery(select);
List<Object> resultList = typedQuery.getResultList();
assertEqualsList(list, resultList);

Query with summary (min,max,avg)

Query query = entityManager.createQuery("select min(s.pint) from SimpleBean s");
Object minActual = query.getSingleResult();
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Object> criteriaQuery = criteriaBuilder.createQuery();
Root from = criteriaQuery.from(SimpleBean.class);
Expression minExpression = criteriaBuilder.min(from.get("pint"));
CriteriaQuery<Object> select = criteriaQuery.select(minExpression);
TypedQuery<Object> typedQuery = entityManager.createQuery(select);
Object minExpected = typedQuery.getSingleResult();
assertEquals(minActual, minExpected);

Query with aggreation (group by)

Query query = entityManager.createQuery("select min(s.pint),s.pbyte from SimpleBean s group by s.pbyte");
List listExpected = query.getResultList();
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Object> criteriaQuery = criteriaBuilder.createQuery();
Root from = criteriaQuery.from(SimpleBean.class);
Expression minExpression = criteriaBuilder.min(from.get("pint"));
Path pbytePath = from.get("pbyte");
CriteriaQuery<Object> select = criteriaQuery.multiselect(minExpression, pbytePath);
CriteriaQuery<Object> groupBy = select.groupBy(pbytePath);
TypedQuery<Object> typedQuery = entityManager.createQuery(select);
List listActual = typedQuery.getResultList();
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