How to use pagination in JPA queries
Use the firstResult(int startPosition) and setMaxResults(int maxResult) of the JPA Query interface.
The firstResult() method sets the offset value in SQL lexicon, meaning the position of the first result to retrieve.
The setMaxResults() method sets the limit value in SQL lexicon, meaning the maximum number of results to retrieve:
@Stateless
public class PartnerInitialLoadRepository {
@Inject private EntityManager em;
public List<PartnerInitialLoad> getNextUnprocessed(Integer pageSize, Integer offset) {
var jpqlQuery="select p from PartnerInitialLoad p where p.status = 'UNPROCESSED' order by p.partnernumber asc";
var query =
em.createNamedQuery(jpqlQuery, PartnerInitialLoad.class);
query.setFirstResult(offset);
query.setMaxResults(pageSize);
return query.getResultList();
}
}
JPA with Hibernate translates this in the following SQL statement in Oracle dialect which uses offset and limit:
select partnerini0_.PARTNER_NUMBER as PARTNER_1_13_,
partnerini0_.COMPLETED_AT as COMPLETE2_13_,
partnerini0_.STATUS as STATUS3_13_
from T_PARTNER_INITIAL_LOAD partnerini0_
where partnerini0_.STATUS is null
or partnerini0_.STATUS = 'UNPROCESSED'
order by partnerini0_.PARTNER_NUMBER asc
offset ? limit ?;
An alternative would be to use native queries, the major drawback is that you make your code dependent on the underlying RDBMS:
public List<PartnerInitialLoad> getNextUnprocessed(Integer pageSize, Integer offset) {
var sqlNativeString =
String.format(
"select * from T_PARTNER_INITIAL_LOAD where STATUS = 'UNPROCESSED' order by PARTNER_NUMBER asc OFFSET %s LIMIT %s",
offset, pageSize);
var query = em.createNativeQuery(sqlNativeString, PartnerInitialLoad.class);
return query.getResultList();
}
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