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Hibernate and Criteria Api generates wrong Join condition

I got following tables. Lets ignore the fact that the relation is done wrong here. I cannot change that.
Each company can have multiple employes and each employe belongs to only one company.
Table: Company
ID
EMPLOYE_ID
10
100
Table: Employe
ID
NAME
100 (Same as EMPLOYE_ID)
John
Now i want to create a relation #OneToMany between Company -> Employe . My entities look as follow
class Company {
#Id
#Column(name = "id", unique = true, nullable = false)
private String id;
#OneToMany(fetch = FetchType.LAZY)
#JoinColumn(name = "EMPLOYE_ID", referencedColumnName = "ID")
private Set<Employe> employees;
}
No matter if i try to create a uniderectional, or biderection relationship by adding also #ManyToOne on my Employe class, when using Criteria api to select all Company entities and their Employes i always end up with a wrong generated SQL query at the point where it joines the tables. The above relation for example creates following:
FROM company company0
INNER JOIN employe employe0 ON company0.id = employe0.employe_id
I tried several approaches, but i end up almost with the same error. It tries either to access a column which does not exist on the table, or joins wrong columns (e.g. id = id). Or by the following exception
Caused by: org.hibernate.MappingException: Repeated column in mapping
for entity: com.Employe column: id (should be mapped with
insert="false" update="false")"}}
What is a simple approach to create a bidrectional relation with the above table structure?
Note: I finally ended up changing the DB schema. Still, it would be interesting if someone could provide an answer for such a case, even if it is based on a not well formed

The central problem is that the described table structures do not allow a 1:n relationship from Company to Employee. According to the table design (especially the design of PKs) above, a company can only have one employee.
However, if the DB design cannot be changed, the following approach using the JoinColumnOrFormula annotation may lead to partial success.
The #JoinColumnOrFormula annotation is used to customize the join between a child Foreign Key and a parent row Primary Key when we need to take into consideration a column value as well as a #JoinFormula.
See https://docs.jboss.org/hibernate/stable/orm/userguide/html_single/Hibernate_User_Guide.html#associations-JoinColumnOrFormula for details.
More concretely with these Entities
#Entity
#Table(name="t_company")
public class Company {
#Id
#Column(name="id")
private Integer id;
#Column(name="employee_id")
private Integer employeeId;
#OneToMany(mappedBy = "company")
private List<Employee> employees;
// ..
}
#Entity
#Table(name = "t_employee")
public class Employee {
#Id
#Column(name = "id")
private Integer id;
#Column(name = "name")
private String name;
#ManyToOne
#JoinColumnOrFormula( column =
#JoinColumn(
name = "id",
referencedColumnName = "employee_id",
insertable = false,
updatable = false
)
)
private Company company;
// ..
}
and this custom repository
#Repository
public class EmployeeRepository {
#Autowired
EntityManager entityManager;
List<Employee> findAll() {
CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Employee> cq = cb.createQuery(Employee.class);
Root<Employee> root = cq.from(Employee.class);
Join<Employee, Company> joinCompany = root.join("company");
TypedQuery<Employee> query = entityManager.createQuery(cq);
return query.getResultList();
}
}
you get the following query:
select
employee0_.id as id1_1_,
employee0_.name as name2_1_
from t_employee employee0_
inner join t_company company1_ on employee0_.id=company1_.employee

Create Hibernat Query with CriteriaBuilder including Join, Group By and Count in Java

In my Java programm I got two entities Invoice and Category (like insurance, salary, car,...). Each Invoice belongs to exactly one Category. Now I want to display a table which lists all existing categories and the number if times they are actually used for an invoice. Like this:
The SQL would look like this:
select categories.name, categories.id, count(invoice.id) as usages
from categories
left join invoice on categories.id = invoice.category_id
group by categories.id
As I'm pretty new to Hibernate I studied the official documentation, but the documentation does only show examples based on a Person and Address relationship. However in my case Category does not have a direct linking to Invoice (it is the other way around: each invoice has a category id). So I played around with the code and came up with the following source code. Which obviously has one serious drawback as I do not get the categories without invoices:
CriteriaBuilder criteriaBuilder = session.getCriteriaBuilder();
CriteriaQuery<CategoryWrapper> criteria = criteriaBuilder.createQuery(CategoryWrapper.class);
Root<Invoice> invoiceRoot = criteria.from(Invoice.class);
Join<Invoice, Category> invoiceJoin = invoiceRoot.join(Invoice_.category);
criteria.select(
criteriaBuilder.construct(
CategoryWrapper.class,
invoiceJoin.get(Category_.id),
invoiceJoin.get(Category_.name),
criteriaBuilder.count(invoiceRoot.get(Invoice_.id))
)
);
criteria.groupBy(invoiceJoin.get(Category_.id));
return session.createQuery(criteria).getResultList();
My question is: How can I get all categories with the number of usages even if no invoice exists for a specific category?
Entities
#Entity
#Table(name = "categories")
public class Category {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private int id;
#Column(name = "name")
private String name;
[... getter and setter ]
}
#Entity
#Table(name = "invoice")
public class Invoice {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private int id;
#Column(name = "date")
private Date date;
#ManyToOne
#JoinColumn(name = "category_id")
private Category category;
#Column(name = "description")
private String description;
#Column(name = "amount")
private String amount;
#Column(name = "income", columnDefinition = "BOOLEAN")
private boolean income;
[...getter and setter...]
}
EDIT1
updated the SQL to use a left join. However using a LEFT join in the java code does not work.
Join<Invoice, Category> invoiceJoin = invoiceRoot.join(Invoice_.category, JoinType.LEFT);
I only get the categories with invoices (as shown in the image above). But in the database more categories are available:
EDIT2
As invoices is the left table and categories is the right table I tried to use RIGHT join
Join<Invoice, Category> invoiceJoin = invoiceRoot.join(Invoice_.category, JoinType.RIGHT);
but that did not work
Caused by: java.lang.UnsupportedOperationException: RIGHT JOIN not
supported
EDIT3
I checked the console output: even if I use a JoinType.LEFT (as shown in EDIT1) the programm will still use a INNER join:
select category1_.id as col_0_0_, category1_.name as col_1_0_, count(invoice0_.id) as col_2_0_ from invoice invoice0_ inner join categories category1_ on invoice0_.category_id=category1_.id group by category1_.id
But why?

How to filter select from table by another table by exclusion principle

My application under Spring Boot v1.5.7
I have 3 entities (schematically):
#Entity
public class Word {
#Id
#GeneratedValue
private Integer id
...
}
#Entity
public class UserWordList {
#Id
#GeneratedValue
private Integer id
#ManyToOne
#JoinColumn(name = "user_id")
private User user;
#ManyToOne
#JoinColumn(name = "word_id")
private Word word;
}
#Entity
public class UserAnotherWordList {
#Id
#GeneratedValue
private Integer id
#ManyToOne
#JoinColumn(name = "user_id")
private User user;
#ManyToOne
#JoinColumn(name = "word_id")
private Word word;
}
And now I need to select all Words for User, but exclude Words placed in user's lists
Native SQL for user_id=1 is
select *
from Word w
left join UserWordList uwl
on w.id = uwl.word_id and uwl.user_id = 1
left join UserAnotherWordList uawl
on w.id = uawl.word_id and uawl.user_id = 1
where uwl.word_id is NULL
and uawl.word_id is NULL
What is a best way to do it? Ideally I would like to use Spring Data features or HQL, but I don't understand how...
UPD
I solve my problem with native query:
#Entity
#NamedNativeQuery(
name = "User.getWordsToProcess",
resultClass = Word.class,
query = "<...native query to select Words...>"
)
public class User {...}
...
public interface UserRepository extends CrudRepository<User, Integer> {
List<Word> getWordsToProcess(Integer userId);
}

Fastest answer is Criteria api (but that is deprecated in hibernate 5.2 and above.)
So you can use Hql :
getSession().createQuery(" select * from UserWordList u left join fetch u.word
left join fetch u.user").list()
And you can use union or create another query to fetch UserAnotherWordList.
Also you can set any restrictions in Hql like below:
Query query = getSession().createQuery(" select * from UserWordList u left join fetch u.word left join fetch u.user us where us.user = :sample").list();
query.setParameter("sample",value);
query.list();

JPA Criteria multiselect with fetch

I have following model:
#Entity
#Table(name = "SAMPLE_TABLE")
#Audited
public class SampleModel implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID")
private Long id;
#Column(name = "NAME", nullable = false)
#NotEmpty
private String name;
#Column(name = "SHORT_NAME", nullable = true)
private String shortName;
#ManyToOne(fetch = FetchType.LAZY, optional = true)
#JoinColumn(name = "MENTOR_ID")
private User mentor;
//other fields here
//omitted getters/setters
}
Now I would like to query only columns: id, name, shortName and mentor which referes to User entity (not complete entity, because it has many other properties and I would like to have best performance).
When I write query:
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<SampleModel> query = builder.createQuery(SampleModel.class);
Root<SampleModel> root = query.from(SampleModel.class);
query.select(root).distinct(true);
root.fetch(SampleModel_.mentor, JoinType.LEFT);
query.multiselect(root.get(SampleModel_.id), root.get(SampleModel_.name), root.get(SampleModel_.shortName), root.get(SampleModel_.mentor));
query.orderBy(builder.asc(root.get(SampleModel_.name)));
TypedQuery<SampleModel> allQuery = em.createQuery(query);
return allQuery.getResultList();
I have following exception:
Caused by: org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list [FromElement{explicit,not a collection join,fetch join,fetch non-lazy properties,classAlias=generatedAlias1,role=com.sample.SampleModel.model.SampleModel.mentor,tableName=USER_,tableAlias=user1_,origin=SampleModel SampleModel0_,columns={SampleModel0_.MENTOR_ID ,className=com.sample.credential.model.User}}]
at org.hibernate.hql.internal.ast.tree.SelectClause.initializeExplicitSelectClause(SelectClause.java:214)
at org.hibernate.hql.internal.ast.HqlSqlWalker.useSelectClause(HqlSqlWalker.java:991)
at org.hibernate.hql.internal.ast.HqlSqlWalker.processQuery(HqlSqlWalker.java:759)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:675)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:311)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:259)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:262)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:190)
... 138 more
Query before exception:
SELECT DISTINCT NEW com.sample.SampleModel.model.SampleModel(generatedAlias0.id, generatedAlias0.name, generatedAlias0.shortName, generatedAlias0.mentor)
FROM com.sample.SampleModel.model.SampleModel AS generatedAlias0
LEFT JOIN FETCH generatedAlias0.mentor AS generatedAlias1
ORDER BY generatedAlias0.name ASC
I know that I can replace fetch with join but then I will have N+1 problem. Also I do not have back reference from User to SampleModel and I do not want to have..

I ran into this same issue, and found that I was able to work around it by using:
CriteriaQuery<Tuple> crit = builder.createTupleQuery();
instead of
CriteriaQuery<X> crit = builder.createQuery(X.class);
A little extra work has to be done to produce the end result, e.g. in your case:
return allQuery.getResultList().stream()
map(tuple -> {
return new SampleModel(tuple.get(0, ...), ...));
})
.collect(toList());

It's been a long time since the question was asked. But I wish some other guys would benefit from my solution:
The trick is to use subquery.
Let's assume you have Applicant in your Application entity (one-to-one):
#Entity
public class Application {
private long id;
private Date date;
#OneToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "some_id")
private Applicant applicant;
// Other fields
public Application() {}
public Application(long id, Date date, Applicant applicant) {
// Setters
}
}
//...............
CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Application> cbQuery = cb.createQuery(Application.class);
Root<Application> root = cbQuery.from(Application.class);
Subquery<Applicant> subquery = cbQuery.subquery(Applicant.class);
Root subRoot = subquery.from(Applicant.class);
subquery.select(subRoot).where(cb.equal(root.get("applicant"), subRoot));
cbQuery.multiselect(root.get("id"), root.get("date"), subquery.getSelection());
This code will generate a select statement for Application, and select statements for Applicant per each Application.
Note that you have to define an appropriate constructor corresponding to your multiselect.

I got the same problem using EclipseLink as the JPA provider : I just wanted to return the id of a mapped entity («User» in Gazeciarz's example).
This can be achieved quite simply by replacing (in the query.multiselect clause)
root.get(SampleModel_.mentor)
with something like
root.get(SampleModel_.mentor).get(User_.id)
Then, instead of returning all the fields of User, the request will only return the its id.
I also used a tuple query but, in my case, it was because my query was returning fileds from more than one entity.

Hibernate: separate sql query for every collection

I have a Person class that has a collection of Contacts. Everything works ok, I get the list of persons with their contacts. However, in log I see that a separate query is made to read collection of every person. That is too bad.
How to make hibernate make a join to read all the data in one query? I use JPA.
This is the person class:
#Entity
#Table(name = "tbl1")
public class PersonItem implements Serializable{
#Id
#Column(name="col1")
private String guid;
.....
#ElementCollection(targetClass = ContactItem.class,fetch=FetchType.EAGER)
#CollectionTable(name="tbl2",joinColumns=#JoinColumn(name="col2"))
private List<ContactItem> contacts;
....
}
This is the contact class
#Embeddable
#Table(name = "tbl2")
public class ContactItem implements Serializable {
#Column(name="col1")
private String guid;
#Column(name="col3")
private String info;
}
This is the way I get the list of persons:
Query query = em.createQuery("Select p from PersonItem p WHERE p.guid IN (:guids)");
query.setParameter("guids", guids);
List<PersonItem> list=query.getResultList();
And this what I see in log (I have three persons in DB):
Hibernate: select personitem0_.col1 as col1_0_, personitem0_.col4 as col2_0_, personitem0_.col2 as col3_0_, personitem0_.col3 as col4_0_ from tbl1 personitem0_ where personitem0_.col1 in (? , ? , ?)
Hibernate: select contacts0_.col2 as col1_1_0_, contacts0_.col1 as col2_1_0_, contacts0_.col3 as col3_1_0_ from tbl2 contacts0_ where contacts0_.col2=?
Hibernate: select contacts0_.col2 as col1_1_0_, contacts0_.col1 as col2_1_0_, contacts0_.col3 as col3_1_0_ from tbl2 contacts0_ where contacts0_.col2=?
Hibernate: select contacts0_.col2 as col1_1_0_, contacts0_.col1 as col2_1_0_, contacts0_.col3 as col3_1_0_ from tbl2 contacts0_ where contacts0_.col2=?

Please, begin from a more simple mapping. Use plural names, and column prefixes.
#Entity
#Table(name = "persons")
public class Person {
#Id
#Column(name = "f_guid")
private String guid;
#OneToMany(mappedBy = "person", fetch = FetchType.EAGER)
private List<Contact> contacts;
}
#Entity
#Table(name = "contacts")
public class Contact {
#Id
#Column(name = "f_guid")
private String guid;
#Column(name = "f_info")
private String info;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "fk_person")
private Person person;
}
Person is associated to contacts by a foreign key fk_person in the contacts table.
Update
Looks like JPQL overrides a default fetching strategy. You need to specify a fetch explicitly
select p from PersonItem p left join fetch p.contacts WHERE p.guid IN (:guids)
If you have duplicates, cause of joins, you can use distinct
select distinct p from PersonItem p left join fetch p.contacts WHERE p.guid IN (:guids)

Try #Fetch on your relation.
Also i would suggest to use #OneToMany relation int this case
#OneToMany(mappedBy = "person", fetch = FetchType.EAGER)
#Fetch(FetchMode.JOIN) //You can use SUBSELECT as well
private List<ContactItem> contacts;
You can read more about fetching strategies here
fetch-“join” = Disable the lazy loading, always load all the collections and entities.
fetch-“select” (default) = Lazy load all the collections and entities.
batch-size=”N” = Fetching up to ‘N’ collections or entities, Not record.
fetch-“subselect” = Group its collection into a sub select statement.