Spring-data, Oliver Gierke's excellent library, has something called a Specification (org.springframework.data.jpa.domain.Specification). With it you can generate several predicates to narrow your criteria for searching.
Can someone provide an example of using a Subquery from within a Specification?
I have an object graph and the search criteria can get pretty hairy. I would like to use a Specification to help with the narrowing of the search, but I need to use a Subquery to see if some of the sub-elements (within a collection) in the object graph meet the needs of my search.
Thanks in advance.
String projectName = "project1";
List<Employee> result = employeeRepository.findAll(
new Specification<Employee>() {
#Override
public Predicate toPredicate(Root<Employee> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
Subquery<Employee> sq = query.subquery(Employee.class);
Root<Project> project = sq.from(Project.class);
Join<Project, Employee> sqEmp = project.join("employees");
sq.select(sqEmp).where(cb.equal(project.get("name"),
cb.parameter(String.class, projectName)));
return cb.in(root).value(sq);
}
}
);
is the equivalent of the following jpql query:
SELECT e FROM Employee e WHERE e IN (
SELECT emp FROM Project p JOIN p.employees emp WHERE p.name = :projectName
)
Related
I've been researching a while about how can I implement an Inner Join using CriteriaBuilder, but the thing is that one of the arguments which both tables have in commons is located inside a jsonb column, so the question is:
How can I INNER JOIN 2 tables by an argument that is located inside a jsonb column called "data" with criteria?
I'll drop down the example code of what I currently have.
public final CriteriaQuery<TutenBookingMacarena> createRatedBookings(
MacarenaBookingSearchFilter filters,
Integer page,
Integer pageSize,
Security security
) {
final CriteriaBuilder builder = entityManager.getCriteriaBuilder();
final CriteriaQuery<TutenBookingMacarena> criteria = builder.createQuery(TutenBookingMacarena.class);
final Root<TutenBookingMacarena> root_Booking = criteria.from(TutenBookingMacarena.class);
Join<TutenBookingMacarena, TutenCaseMacarena> rootJoin = root_Booking.join(String.valueOf(
builder.function("jsonb_extract_path_text",
String.class,
root_Booking.<String>get("data"),
builder.literal("caseId")
)
));
...
}
But when executing those lines of code I get an error message that says the named attribute can not be found. Any idea what's wrong here?
I want to use criteriaUpdate to create an update query like this:
UPDATE <SOME TABLE>
SET SELECTED = !SELECTED
WHERE
[DYNAMIC QUERY HERE]
The closest I could get was with the code:
public <T> Query createRevertSelectionQuery(Class<T> clazz, EntityManager em, Specification<T> s) {
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaUpdate<T> criteriaUpdate = cb.createCriteriaUpdate(clazz);
Root<T> root = criteriaUpdate.from(clazz);
Predicate p = cb.and(new Predicate[] {s.toPredicate(root, null, cb)});
Expression<Boolean> e =cb.not((root.get("selected").as(Boolean.class)));
Path<Boolean> selected = root.get("selected");
criteriaUpdate.set(selected, e);
criteriaUpdate.where(p);
Query q = em.createQuery(criteriaUpdate);
return q;
}
but it fails because I get the following query:
update com.redknee.suspense.mgt.model.Moc as generatedAlias0
set generatedAlias0.selected = generatedAlias0.selected <> true
where
[dynamic query]
giving me the error
org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected token: <> near line 1, column 118
Anyone can help please?
I am not sure if this is a bug or if it is just not meant to be used this way .
In where-clause NOT and any other operands work like a charm. But, no matter what you try Hibernate query builder seems always to optimize those parenthesis away (in my opinion it might still be a good habit to always use parenthesis but its only an opinion).
One way to force parenthesis is to use JPA Subquery. See below example. Note that i have slightly altered the JPA object names by my own taste and not included the Specification because it is not relevant to this solution:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaUpdate<T> update = cb.createCriteriaUpdate(clazz);
Root<T> from = update.from(clazz);
Path<Boolean> selected = from.get("selected");
// Subquery just "joins back" to the same row and
// returns a negated boolean value of "selected" from the original row
Subquery<Boolean> subSelect = update.subquery(Boolean.class);
Root<T> subFrom = subSelect.from(clazz);
subSelect.select(cb.not(selected));
subSelect.where(cb.equal(from.get("id"), subFrom.get("id")));
update.set(selected, subSelect);
I have following issue. I am using Jquery Datatable serverside and I am now implementing the search box. But I have an issue there in special case, when a dataset has an attribute, what is "null". So the dataset will not be found although it should found cos it matches on one attibute.
The situtation in beginning is like follows. You see there is a dataset with apprentice Fabio Bartels, who has not Fachrichtung. And a dataset with Viktoria.
Now when I search for Viktoria, the filter works as expected:
When I search for Fabio, then Dataset is not found:
=====
The problem I have is, that I don't know how to handle the filter, that a attribute will only be validated against the search string when the attribute is not null.
=====
Serverside Java Classes see like follows:
QueryClass:
class ContractSearchQuery {
private static QContract contract = QContract.contract;
static BooleanExpression getPredicate(final ContractSearch filter) {
BooleanExpression predicate;
if (filter == null || filter.isEmpty()) {
// SHOW ALL PREDICATE ...
} else {
final String search = filter.getSearch();
final List<BooleanExpression> expressions = new ArrayList<BooleanExpression>();
// EXPRESSIONS CURRENTLY ONLY ON AUSZUBILDENDER AND FACHRICHTUNG
// FOR SHOWCASE
expressions.add(containsApprenticeName(search)); // AUSZUBILDENDER
expressions.add(containsSpecialisation(search)); // FACHRICHTUNG
BooleanExpression expression = expressions.get(INTEGER_ZERO);
for (int i = 1; i < expressions.size(); i++) {
expression = expression.or(expressions.get(i));
}
predicate = expression;
}
return predicate;
}
private static BooleanExpression containsApprenticeName(final String search) {
final BooleanExpression expLastName = contract.apprentice.lastName.containsIgnoreCase(search);
final BooleanExpression expFirstName = contract.apprentice.firstName.containsIgnoreCase(search);
return expLastName.or(expFirstName);
}
private static BooleanExpression containsSpecialisation(final String search) {
return contract.companyOccupationCombination.occupationCombination.specialisation.name.containsIgnoreCase(search);
}
}
Spring-Data-Repository Call:
final PageRequest pageRequest = new PageRequest(firstResult / maxResults, maxResults, orderSort);
final Page<Contract> page = contractRepository.findAll(predicate, pageRequest);
return page.getContent();
=======
Database:
By the way I recognized when I do direct request against my db with joining Specialisation Table, then I only get Fabio as record, when not joining Specialisation, I get all three persons. Maybe somethings to do with my issue:
select a.first_name, a.last_name from contract c
join company_occupation_combination coc on c.company_occupation_combination = coc.id
join occupation_combination oc on coc.occupation_combination = oc.id
join apprentice a on c.apprentice = a.id
Result:
"Fabio";"Bartels"
"Viktoria";"Kruczek"
"Lina";"Ehleiter"
With Join:
select a.first_name, a.last_name from contract c
join company_occupation_combination coc on c.company_occupation_combination = coc.id
join occupation_combination oc on coc.occupation_combination = oc.id
join specialisation s on oc.specialisation = s.id
join apprentice a on c.apprentice = a.id
Result: "Viktoria";"Kruczek"
====
EDIT:
Okay, on db site I found out (with Hibernate and JPA I start forgetting SQL-Basices ;-)), that I need a left join for the nullable relation, so my query should result to an sql like:
select a.first_name, a.last_name from contract c
join company_occupation_combination coc on c.company_occupation_combination = coc.id
join occupation_combination oc on coc.occupation_combination = oc.id
left join specialisation s on oc.specialisation = s.id
join apprentice a on c.apprentice = a.id
====
So my question is, how can I manage left Join when I have a Query-Class using QueryDSL and Spring-Data-Repository like mentioned above?
If you really need left join, you can't achieve that via predicate (instead it is possible via sub-query)
To be able to do left-join, you will need JPAQuery.
Assuming you have already configured repositories, and able to use EntitiManager, implement ContractRepositoryCustom , so that in your implementation you can have
#PersistenceContext(unitName = "unitname")
protected EntityManager entityManager;
public List<Contract> findAllContracts() {
return new JPAQuery(entityManager, HQLTemplates.DEFAULT)
.from(QContract.contract)
.join(QContract.contract.companyOccupationCombination, QCompanyOccupationCombination.companyOccupationCombination)
.join(QCompanyOccupationCombination.companyOccupationCombination.occupationCombination, QOccupationCombination.occupationCombination)
.leftJoin(QOccupationCombination.occupationCombination.specialization, QSpecialization.specialization)
.join(QSpecialization.specialization.apprentice, QApprentice.apprentice)
.list(QContract.contract);
}
And for pagination you always apply limit(maxResults) and offset(firstResult)
I really like working with Spring-Data and Query-DSL, cos it makes my code really tidy. But I am really suprised, that for the case of nullable references there seems no solution. Sure you can use another solution like #vtorosyan mentioned and thank you again for that solution, but when you project is builded up with combination of QueryDSL and Spring-Data, you really don't want to bring a second style in your application.
But I needed a solution, so I did now the follows.
The point of the issue was, that when I used data from a nullable entity, a join has been executed what hided the datasets, who had a null reference on it, see examples above. What I now did and I hope I will not get another issue then with that solution on later time of that project. I did the null references to not null and defined something like null-record.
Example I added a record for specialisation like
ID NAME
0 Keine
Instead of null I now use that record what has until now following effects:
First my table shows now "Keine" (engl. "None") for all attributes what are not set. It looks more consistent when having a textoutput then empty string.
Now I can explicitly search for "Keine", when I am interested for data records what have no specialisation set.
And my searchbox works as expected for records, which have no speciafication set. (THAT WAS MY ISSUE FROM BEGINNING WHAT I WANTED TO SOLVE):
Additional to that searchbox I use a modal dialog for filtering. Now I can explicitly filter "Keine" for "nullable" records:
If you think there is another good solution for that issue without rebuild code using Spring-Data and QueryDSL konsequently, don't hesitate to post ;-)
is this valid HQL?
If not (i assume not since im getting wrong result back). How/can i achieve this generic slect transaction?
String hql = "SELECT * from users Where :searchCriteria = :searchString";
List q = session.createSQLQuery(hql).addEntity(Users.class)
.setParameter("searchField", searchCriteria)
.setParameter("searchString", searchString).list();
Try this hql,
Criteria cr= session.createCriteria(Users.class);
cr.add(Restrictions.eq("searchField", searchCriteria);
cr.add(Restrictions.eq("searchString", searchString);
List<Users> user_data=(List<Users>)cr.list();
I am using this query:
return from oi in NHibernateSession.Current.Query<BlaInteraction>()
select new BlaViewModel
{
...
NoPublications = oi.Publications.Count(),
...
};
BlaInteraction contains an IList of publications (i.e. entities). To determine the number of publications one does not really need to do all the joins for a publication. Can I prevent nhibernate from using joins in the generated sql (e.g. using projection???) somehow?
Thanks.
Christian
PS:
This is what NH produces (slightly adapted):
select cast(count(*) as INT) from RelationshipStatementPublications publicatio21_, Publication publicatio22_ inner join Statements publicatio22_1_ on publicatio22_.StatementId=publicatio22_1_.DBId where publicatio21_.StatementId = 22762181 and publicatio21_.PublicationId=publicatio22_.StatementId
This is what would be sufficient:
select cast(count(*) as INT) from RelationshipStatementPublications publicatio21_ where publicatio21_.StatementId = 22762181
Why can't you just create another query ?
Session.QueryOver<Publication>().Where(x => x.BlaInteractionId == idSentAsParameter).Select(Projections.RowCount()).SingleOrDefault<int>();
I think that's will work
return from oi in NHibernateSession.Current.Query<BlaInteraction>()
select new BlaViewModel
{
...
NoPublications = Session.QueryOver<Publication>().Where(x => x.BlaInteractionId == oi.Id).Select(Projections.RowCount()).SingleOrDefault<int>();
...
};
Another edit, have you tried lazy="extra" ?
Ok the best solution I have found so far is to use a FNH Formula:
mapping.Map(x => x.NOPublications).Formula("(select count(distinct RelationshipStatementPublications.PublicationId) from RelationshipStatementPublications where RelationshipStatementPublications.StatementId = DBId)");
public virtual int NOPublications {get; private set;}
when I map from the domain to the view model I use:
NoPublications = oi.NOPublications,
Christian