How to filter by faculty name? - jpa

Question

I want to implement lazy record loading on a Primefaces DataTable (version 7). I have two entities, one is called Faculties and the other is Careers, which are related. The datatable correctly shows the list of all the races (includes pagination and filtering), the problem I have is that I do not know how to filter the races by the name of a certain faculty, since I do not know how to include the join in the query that I leave then.
Could you guide me on how to solve it please?
Entity Faculties
public class Facultades implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "idfacultad")
private Integer idfacultad;
#Basic(optional = false)
#NotNull
#Size(min = 1, max = 100)
#Column(name = "nombre")
private String nombre;
#Size(max = 20)
#Column(name = "abreviatura")
private String abreviatura;
#OneToMany(cascade = CascadeType.ALL, mappedBy = "idfacultad")
private List<Carreras> carrerasList;}
Entity Carreras
public class Carreras implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "idcarrera")
private Integer idcarrera;
#Basic(optional = false)
#NotNull
#Size(min = 1, max = 150)
#Column(name = "nombre")
private String nombre;
#Basic(optional = false)
#NotNull
#Column(name = "tipo")
private int tipo;
#JoinColumn(name = "idfacultad", referencedColumnName = "idfacultad")
#ManyToOne(optional = false)
private Facultades idfacultad;}
Query findByParams
public List<Carreras> findByParams(int start, int size, String sortField, SortOrder sortOrder, Map<String, Object> filters) {
CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
CriteriaQuery<Carreras> criteriaQuery = criteriaBuilder.createQuery(Carreras.class);
Root<Carreras> root = criteriaQuery.from(Carreras.class);
CriteriaQuery<Carreras> select = criteriaQuery.select(root);
Join<Carreras, Facultades> facultad = root.join("idfacultad");
if (sortField != null) {
criteriaQuery.orderBy(sortOrder == SortOrder.DESCENDING ? criteriaBuilder.asc(root.get(sortField)) : criteriaBuilder.desc(root.get(sortField)));
}
if (filters != null && filters.size() > 0) {
List<Predicate> predicados = new ArrayList<>();
filters.entrySet().forEach((entry) -> {
String key = entry.getKey();
Object val = entry.getValue();
if (!(val == null)) {
// Construimos la expresion con los predicados que si existan
Expression<String> expresion = root.get(key).as(String.class);
Predicate predicado = criteriaBuilder.like(criteriaBuilder.lower(expresion), "%" + val.toString().toLowerCase() + "%");
predicados.add(predicado);
}
});
if (predicados.size() > 0) {
criteriaQuery.where(criteriaBuilder.and(predicados.toArray(new Predicate[predicados.size()])));
}
}
// Creamos la consulta
TypedQuery<Carreras> consulta = em.createQuery(select);
consulta.setFirstResult(start);
consulta.setMaxResults(size);
return consulta.getResultList();
}

Answer 1

You need to manually check if the filter key equals the Facultades object, and in that case create a predicate on the joined expression that you have already created:
if (key.equals("Facultad")) {
expresion = facultad.get("nombre").as(String.class);
} else {
expresion = root.get(key).as(String.class);
}