I have the following relevant JPA annotated classes in a Spring-Boot JPA enabled project (All Groovy Code):
#Entity
abstract class Character {
#Id
String id;
String name;
#ElementCollection(targetClass = Episode)
#Enumerated(EnumType.ORDINAL)
Collection<Episode> appearsIn;
}
#Entity(name = "Human")
public class Human extends Character {
String homePlanet;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "favorite_droid_id")
Droid favoriteDroid;
}
public enum Episode {
PHANTOM_MENACE,
ATTACK_OF_THE_CLONES,
REVENGE_OF_THE_SITH,
A_NEW_HOPE,
EMPIRE_STRIKES_BACK,
RETURN_OF_THE_JEDI,
THE_FORCE_AWAKENS
}
When I attempt to execute the following JPA Query:
def query = em.createQuery("from Human h where h.appearsIn in (:episodes)");
query.setParameter("episodes", EnumSet.of(Episode.THE_FORCE_AWAKENS));
def result = query.getResultList();
The generated SQL statement does not seem to have the alias to the Character table or the column name for appears_in:
select human0_.id as id2_0_, human0_.name as name3_0_, human0_.favorite_droid_id as favorite6_0_, human0_.home_planet as home_pla5_0_
from character human0_
cross join character_appears_in appearsin1_
where human0_.dtype='Human' and human0_.id=appearsin1_.character_id and (. in (?))
I have also tried using equals instead of in, with the same behavior:
from Human h where h.appearsIn = :episode
Produces the following SQL:
select human0_.id as id2_0_, human0_.name as name3_0_, human0_.favorite_droid_id as favorite6_0_, human0_.home_planet as home_pla5_0_
from character human0_
cross join character_appears_in appearsin1_
where human0_.dtype='Human' and human0_.id=appearsin1_.character_id and .=?
Any help is greatly appreciated.
Your query is invalid - as #Neil Stockton pointed out, by writing h.appearsIn in (:episodes) you are saying "collection in collection" which does not make sense.
You should rather declare a "collection member variable" like this:
select distinct h
from Human h
join h.appearsIn ai
where ai in (:episodes)
ai represents a single element of appearsIn (like an iterator).
Related
I have a entity class
public class Hex {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY, generator = "native")
#Column(name = "hex_id")
private Long hexId;
#Column(name = "class")
String vehicleClass;
#Column(name = "manufacturer")
String manufacturer;
}
I need distinct manufacturer on basis of Vehicleclass, I am using below function
List<Hex> findManufacturerDistinctByVehicleClass(String classId);
But this return Distinct Hex objects on the basis of vehicle ID ,I observed the query in console and it was fetching results based on distinct primary key and applying a where clause on class
select
distinct hex0_.hex_id as hex_id1_1_,
hex0_.Manufacturer as manufact2_1_,
hex0_.class as class3_1_
from
hex hex0_
where
hex0_.class=?
I can do it by using #Query but I am looking for a derived query solution and if cannot be done then why
It seems this is how derived queries work:
Anything between find and By is skipped, except for the Distinct keyword
Distinct will apply the distinct keyword to the select clause of the SQL query
Everything after By is used in the where clause as a filter (it won't affect the select clause)
I think you already know this but I guess you have two options:
The #Query annotation:
#Query("select distinct manufacturer from Hex where ...")
List<String> findManufacturerDistinctByVehicleClass(String classId);
Projections:
interface ManufacturerProjection {
String getManufacturer();
}
List<ManufacturerProjection> findManufacturerDistinctByVehicleClass(String classId);
I have the following 2 classes using JTA transaction type with openjpa & a derby embedded db. What I want is to get the parent Organisation & the requested WSpace in one query when I only have the WSpace id. I am quite new to JPA so am learning as I go and have been struggling with 'q2' query. I have been using queries 'q0' & 'q1' to debug and check the items do exist in the db. 'q0' returns 1 object as does 'q1', whereas 'q2' returns 0 objects
I have tried a variety of entity setups and different queries but nothing has worked yet.
Orignally the WSpace class did not have an Organisation field as it didn't seem necessary for persisting or selecting, but I added it (along with the mappedby parameter) incase it was needed for the query to work, but nothing has changed.
back to the original question how can I get this to work so it returns the parent object with the single child being requested
SELECT o FROM Organisation o JOIN FETCH o.spaces w WHERE w.id = :id
Here are my classes
#Entity
public class Organisation implements MyObjects
{
#Id
#NotNull
private Integer id;
private String name;
#OneToMany( mappedBy = "organisation",
cascade = { CascadeType.PERSIST, CascadeType.MERGE } )
private List<WSpace> spaces;
//getters/setter below
}
And
#Entity
public class WSpace implements MyObjects
{
#Id
#NotNull
private Integer id;
private String name;
#ManyToOne
private Organisation organisation;
#OneToMany
private List<Application> apps;
//getters/setter below
}
class DAO
{
...
public void foo( Integer id )
{
....
String q0 = "SELECT o FROM Organisation o WHERE o.id = 49068";
List<Organisation> res0 = em.createQuery( q0, Organisation.class ).getResultList();
String q1 = "SELECT w FROM WSpace w WHERE w.id = " + id;
List<WSpace> res1 = em.createQuery( q1, WSpace.class ).getResultList();
String q2 = "SELECT o FROM Organisation o "
+ "JOIN FETCH o.spaces w WHERE w.id = " + id;
List<Organisation> res2 = em.createQuery( q2, Organisation.class ).getResultList();
...
}
}
Have you tried to look in the logs for output of your q2 query?
I am learning JPA too and was dealing with Criteria and QL queries quite recently.
So after having pretty same problems with joins, I started checking logs and it was pretty clear, what the issues were, since logs showed up translated to SQL queries.
Another thing to look, how are you generating your Entities? I used Netbeans generating it for me. Also, many to many relations mignt have helper class generated too, I saw it in one of the projects.
Hope it helps..
The query you're looking for is probably this:
SELECT w FROM WSpace w LEFT JOIN FETCH w.organisation where w.id=:id
with query.setParameter("id", id); to bind the id parameter to the query. This effectively tells the persistence provider to fetch the WSpace.organisation relation while querying for WSpace entities in the same query. Using the LEFT [OUTER] keword (OUTER being optional) in front of the JOIN FETCH keywords tells your persistence provider to select WSpace objects even if there are no matching Organisation records for your WSpace.organisation relation.
I am trying to find the maximum value of a Date column in mySQL DB using hibernate query language with join
#Query("select o.techid, CAST(MAX(o.last_modified) AS DATE)
from com.dw.model.user.User as u
left join com.dw.model.order.Order as o
on u.username=o.techid group by o.techid")
List<User> findUsers();
Model class =
#Entity(name = "orders")
#Scope("prototype")
#Component
#JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class)
public class Order {
#Id
private long orderNumber;
private Date last_modified;
I am getting this error :-
Caused by: java.lang.IllegalStateException: DOT node with no left-hand-side!
Can anyone please help me out by telling me how to write this in Hibernate?
Remove your package names. An entity is defined by its name only. Dots are used for properties and links between tables (when defined as a #ManyToOne* property).
select o.techid, CAST(MAX(o.last_modified) AS DATE)
from User as u
left join Order as o
on u.username=o.techid group by o.techid
Think Classes and Properties, not columns, when you write HQL.
Try following solution, this should work
SELECT o.techid, CAST(MAX(o.last_modified) AS DATE)
FROM User u LEFT JOIN u.order o GROUP BY o.techid
Say I want to get all rows of the MyEntity that have an id lower than 10. This entity contains a list of Another entity. I would like this list to be fetched only by a subset of the listAnother. This subset containing only Another where the user contained in it is a specific one.
Basically in SQL it would be like this :
SELECT * FROM myentity m
LEFT JOIN another a
ON m.idTable=a.my_entity
AND a.user = "test1"
WHERE m.idTable < 10;
I didn't manage however to translate this query to jpql.
My entities being like this :
#Entity
public class MyEntity implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int idTable;
#OneToMany(mappedBy = "myEntity")
private List<Another> listAnother;
}
#Entity
public class Another implements Serializable {
#Id
private int idAnother;
// bi-directional many-to-one association to Thethread
#ManyToOne(fetch = FetchType.LAZY)
private MyEntity myEntity;
#ManyToOne(fetch = FetchType.LAZY)
private User user;
}
#Entity
public class User implements Serializable {
#Id
private String username;
}
In jpa I could do this :
SELECT m FROM MyEntity where m.idTable < 10;
And then for each entity I get from this list call this:
SELECT a FROM Another Where a.user.username=:'test' AND a.myEntity=:entity;
However I would like to do it all at once in one query. Can I do this with criteria ? I didn't take the time to learn it but if it's possible then I will.
JPQL and Critaria API are equal in terms of what you can express with them. What is possible with JPQL is possible with Criteria and vice versa.
With JPQL, you can simply combine your 2 queries into one in this way:
SELECT a FROM Another a Where a.user.username=:test AND a.myEntity.idTable < 10
You can use dot notation (.) to join multiple entities in the query, provided that the relationship is X-to-one. If you have X-to-many relationship, you need to use JPQL JOIN, which is not very complicated. Example with (LEFT) JOIN:
SELECT m FROM MyEntity m LEFT JOIN m.listAnother a Where a.user.username=:test AND m.idTable < 10
The result is of course not equal - in first case you will get list of Another entities and you can get MyEntity by a.myEntity, in the second case you will get list of MyEntity, which all have at least one Another entity with given user
In hibernate you can use Filters and FilterJoinTable. Here you can read how to do that. Similar problem was solved here.
You need to extend the logic which you applied to check the username (a.user.username=:'test') which was for many-to-one relation between anything and user by taking it one level up to myEntity and then using it for one-to-many relation as well -
SELECT m FROM MyEntity where m.idTable < 10 and (m.listAnother.user.username=:'test')
The join condition "m.listAnother.myEntity=:entity" wouldn't be needed now as in our query we have started from the specific myEntity and then moved down to listAnother.user.username .
I don't have the table definitions to try this query myself, exact SQL may require some tweaks - but logically it should work like the way I showed above, i.e. just the way you joined Another with User, the same way you can join MyEntity with Another by just traversing down the child listAnother.
When performing a hibernate query in HQL using a join and subsequently calling query.list to return the list of matched objects, I am ending up with a list of actual Object instances (i.e. query.list().get(0).getClass() == Object.getClass()) instead of instances of the expected object.
Running the query without the join returns objects of the expected type correctly and they can be cast and used appropriately.
So far my searches have not turned up anything about what could be causing this. Is there something else I need to do when using a join in hql to ensure the object is mapped correctly?
Edit: Added code excerpts below. I had to change all the names and attempt to extract only the relevant portions (the real code is not really about cars).
Working query:
from Car car where car.name like :name
Non-working query:
from Car car left join car.occupants occupant where car.name like :name OR (occupant.name like :oname)
Car entity:
#Entity
#Table(uniqueConstraints = {#UniqueConstraint(columnNames = {"someId"}),
#UniqueConstraint(columnNames = {"someOtherId"})})
public class Car extends SomeParentEntity
{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(nullable = false, length = 64)
private String someId;
#Column(length = 64)
private String name;
// ... Many columns and mappings removed ...
#OneToMany(mappedBy = "car", fetch = FetchType.LAZY)
private List<Occupant> occupants;
// ...
}
Occupant entity:
#Entity(name = "car.Occupant")
#Table(uniqueConstraints = {#UniqueConstraint(columnNames = { "name" }) })
public class User extends SomeParentEntity
{
#ManyToOne
#JoinColumn(name = "carId", nullable = false)
private Car car;
#Column(length = 64, nullable = false)
private String name;
// ... Many mappings / columns removed ...
}
Your JOIN in the HQL is making Hibernate retrieve two types of objects. You can see this if you activate the SQL logging.
Assuming you have a X-to-X relation in your entity, the problem should go away if you change the query to use
... JOIN FETCH entity.relation ...
Why are you using explicit left join btw.
from Car car left join car.occupants occupant where car.name like :name OR (occupant.name like :oname)
I think we can simple use:
from Car car where car.name like :name or car.occupant.name like :oname
Then the query.list should give you List of object which should be casted back to List of car
+1's all around to the other answerers for your help, it is much appreciated.
However, the solution turned out to be very simple. The query just needed to have the select specified at the beginning for the join case in order to narrow the field (I assume).
So the non-working query:
from Car car left join car.occupants occupant where car.name like :name OR (occupant.name like :oname)
Becomes:
select car from Car car left join car.occupants occupant where car.name like :name OR (occupant.name like :oname)