Java using filtering at different models before and after the projection

Question

Consider the following JAVA model for hibernate:

@Entity
@Table
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Long id;

    @Column
    public String firstName;

    @Column
    public String lastName;

    @Column
    public Boolean active;
}

and the following model for API serialization (using spring boot rest controller):

public class PersonVO {
    public Long id;
    public String fullName;
}

What i want is to:

• Have some filtering applied at the Person (statically defined)
• Have some filtering applied at the PersonVO (get from @RequestParam)

In C# .NET i could make like:

IQueryable<Person> personsQuery = entityFrameworkDbContext.Persons;
// FIRST POINT - Here i could make some predefined filtering like 'only active', 'from the same city'... at the database model
personsQueryWithPreDefinedFilters = personsQuery.Where(person => person.active == true);


IQueryable<PersonVO> personsProjectedToVO = personsQueryWithPreDefinedFilters.Select(person => new PersonVO()
{
    id = person.id,
    fullName = person.firstName + " " + person.lastName
});
// SECOND POINT - At this point i could add more filtering based at PersonVO model
if (!String.IsNullOrWhiteSpace(fullNameRequestParameter)) {
    personsProjectedToVO = personsProjectedToVO.Where(personVO => personVO.FullName == fullNameRequestParameter);
}

// The generated SQL at database is with both where (before and after projection)
List<PersonVO> personsToReturn = personsProjectedToVO.ToList();

What i got in Java is:

CriteriaBuilder cb = this.entityManager.getCriteriaBuilder();
CriteriaQuery<PersonVO> cq = cb.createQuery(PersonVO.class);
Root<Person> root = cq.from(Person.class);
// FIRST POINT - Here i could make some predefined filtering like 'only active', 'from the same city'... at the database model
cq.where(cb.equal(root.get(Person_.active), true));         

Expression<String> fullName = cb.concat(root.get(Person_.firstName), root.get(Person_.lastName));
cq.select(cb.construct(
        PersonVO.class,
        root.get(Person_.id),
        fullName
        ));
// SECOND POINT - At this point i could add more filtering based at PersonVO model??? HOW???
if (fullNameRequestParameter != null) {
    cq.where(cb.equal(fullName, fullNameRequestParameter));
// i only could use based at the fullName expression used, but could i make a Predicate based only on PersonVO model without knowing or having the expression?
}

I want to have separated the "projection to the VO model" from the "where expression" applied to it, but have it indirectly applied if used a projected column (like fullName).

Is this possible in Java? Using what? Criteria? Querydsl? Stream? (don't get necessarily stick to the java sample)

Answer 1

Using this http://www.jinq.org/ library i could do it and get applied to the hibernate (and consequently database).

JinqJPAStreamProvider jinqJPAStreamProvider = new JinqJPAStreamProvider(this.entityManager.getMetamodel());

JPAJinqStream<Person> personStream = jinqJPAStreamProvider.streamAll(this.entityManager, Person.class);
personStream = personStream.where(person -> person.getFirstName().equals("Joao"));

// The only trouble is that we have to register the Model we want to project to (i believe it could be solved with reflection)
jinqJPAStreamProvider.registerCustomTupleConstructor(PersonVO.class.getConstructor(Long.class, String.class), PersonVO.class.getMethod("getId"), PersonVO.class.getMethod("getFullName"));

JPAJinqStream<PersonVO> personVOStream = personStream.select(person -> new PersonVO(person.getId(), person.getFirstName() + person.getLastName()));
personVOStream = personVOStream.where(person -> person.getFullName().equals("JoaoCarmo"));

List<PersonVO> resultList = personVOStream.toList();

Thanks all for the help!