I cannot get the below OneToMany mappings to work properly, even though they are supposedly validated (by hibernate.ddl-auto=validate). I can insert all entities in the application with no problems, but while doing a findAll or findById, the queries Hibernate generates for me are wrong and result in exceptions. This is very likely due to a problem with my OneToMany mappings, or lack of a ManyToOne mapping but I don't see how to make it work.
Currently, the following tables exist in my postgres12 database:
CREATE TABLE battlegroups (
id uuid,
gameworld_id uuid,
name varchar(255),
PRIMARY KEY(id)
);
CREATE TABLE battlegroup_players (
id uuid,
battlegroup_id uuid,
player_id integer,
name varchar(255),
tribe varchar(255),
PRIMARY KEY (id)
);
CREATE TABLE battlegroup_player_villages(
battlegroup_id uuid,
player_id integer,
village_id integer,
x integer,
y integer,
village_name varchar(255),
tribe varchar(255),
PRIMARY KEY(battlegroup_id, player_id, village_id, x, y)
);
These are mapped to the following entities in Kotlin:
#Entity
#Table(name = "battlegroups")
class BattlegroupEntity(
#Id
val id: UUID,
#Column(name = "gameworld_id")
val gameworldId: UUID,
val name: String? = "",
#OneToMany(mappedBy = "battlegroupId", cascade = [CascadeType.ALL],fetch = FetchType.EAGER)
private val players: MutableList<BattlegroupPlayerEntity>)
#Entity
#Table(name = "battlegroup_players")
class BattlegroupPlayerEntity(#Id
val id: UUID,
#Column(name = "battlegroup_id")
val battlegroupId: UUID,
#Column(name = "player_id")
val playerId: Int,
val name: String,
#Enumerated(EnumType.STRING)
val tribe: Tribe,
#OneToMany(mappedBy= "id.playerId" , cascade = [CascadeType.ALL], fetch = FetchType.EAGER)
val battlegroupPlayerVillages: MutableList<BattlegroupPlayerVillageEntity>)
#Entity
#Table(name = "battlegroup_player_villages")
class BattlegroupPlayerVillageEntity(
#EmbeddedId
val id: BattlegroupPlayerVillageId,
#Column(name ="village_name")
val villageName: String,
#Enumerated(EnumType.STRING)
val tribe: Tribe)
#Embeddable
data class BattlegroupPlayerVillageId(
#Column(name = "battlegroup_id")
val battlegroupId: UUID,
#Column(name = "player_id")
val playerId: Int,
#Column(name = "village_id")
val villageId: Int,
val x: Int,
val y: Int
): Serializable
This is the SQL hibernate generates when I do a findAll/findById on a battlegroup:
select
battlegrou0_.id as id1_2_0_,
battlegrou0_.gameworld_id as gameworl2_2_0_,
battlegrou0_.name as name3_2_0_,
players1_.battlegroup_id as battlegr2_1_1_,
players1_.id as id1_1_1_,
players1_.id as id1_1_2_,
players1_.battlegroup_id as battlegr2_1_2_,
players1_.name as name3_1_2_,
players1_.player_id as player_i4_1_2_,
players1_.tribe as tribe5_1_2_,
battlegrou2_.player_id as player_i2_0_3_,
battlegrou2_.battlegroup_id as battlegr1_0_3_,
battlegrou2_.village_id as village_3_0_3_,
battlegrou2_.x as x4_0_3_,
battlegrou2_.y as y5_0_3_,
battlegrou2_.battlegroup_id as battlegr1_0_4_,
battlegrou2_.player_id as player_i2_0_4_,
battlegrou2_.village_id as village_3_0_4_,
battlegrou2_.x as x4_0_4_,
battlegrou2_.y as y5_0_4_,
battlegrou2_.tribe as tribe6_0_4_,
battlegrou2_.village_name as village_7_0_4_
from
battlegroups battlegrou0_
left outer join
battlegroup_players players1_
on battlegrou0_.id=players1_.battlegroup_id
left outer join
battlegroup_player_villages battlegrou2_
on players1_.id=battlegrou2_.player_id -- ERROR: comparing integer to uuid
where
battlegrou0_.id=?
This results in an exception:
PSQLException: ERROR: operator does not exist: integer = uuid
Which makes perfect sense, since it is comparing the battlegroup_players id, which is a uuid, to the battlegroup_player_villages player_id, which is an integer. It should instead be comparing/joining on the battlegroup_player's player_id to the battlegroup_player_village's player_id.
If I change the sql to reflect that and manually execute the above query with the error line replaced:
on players1_.player_id=battlegrou2_.player_id
I get exactly the results I want. How can I change the OneToMany mappings so that it does exactly that?
Is it possible to do this without having a BattlegroupPlayerEntity object in my BattlegroupPlayerVillageEntity class?
Bonus points if you can get the left outer joins to become regular inner joins.
EDIT:
I tried the current answer, had to slightly adjust my embedded id because my code could not compile otherwise, should be the same thing:
#Embeddable
data class BattlegroupPlayerVillageId(
#Column(name = "battlegroup_id")
val battlegroupId: UUID,
#Column(name = "village_id")
val villageId: Int,
val x: Int,
val y: Int
): Serializable {
#ManyToOne
#JoinColumn(name = "player_id")
var player: BattlegroupPlayerEntity? = null
}
Using this still results in a comparison between int and uuid, for some reason.
Schema-validation: wrong column type encountered in column [player_id] in table [battlegroup_player_villages]; found [int4 (Types#INTEGER)], but expecting [uuid (Types#OTHER)]
Interestingly, if I try to put a referencedColumnName = "player_id" in there, I get a stackoverflow error instead.
I did some digging and found some issues with the mapping as well as classes, I will try to explain as much as possible.
WARNING!!! TL;DR
I will use Java for code, I hope that should not be a problem converting to kotlin.
There are some issues with classes also(hint: Serializable), so classes must implements Serializable.
Used lombok to reduce the boilerplate
Here is the changed BattleGroupPlayer entity:
#Entity
#Getter
#NoArgsConstructor
#Table(name = "battle_group")
public class BattleGroup implements Serializable {
private static final long serialVersionUID = 6396336405158170608L;
#Id
private UUID id;
private String name;
#OneToMany(mappedBy = "battleGroupId", cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.LAZY)
private List<BattleGroupPlayer> players = new ArrayList();
public BattleGroup(UUID id, String name) {
this.id = id;
this.name = name;
}
public void addPlayer(BattleGroupPlayer player) {
players.add(player);
}
}
and BattleGroupVillage and BattleGroupVillageId entity
#AllArgsConstructor
#Entity
#Getter
#NoArgsConstructor
#Table(name = "battle_group_village")
public class BattleGroupVillage implements Serializable {
private static final long serialVersionUID = -4928557296423893476L;
#EmbeddedId
private BattleGroupVillageId id;
private String name;
}
#Embeddable
#EqualsAndHashCode
#Getter
#NoArgsConstructor
public class BattleGroupVillageId implements Serializable {
private static final long serialVersionUID = -6375405007868923427L;
#Column(name = "battle_group_id")
private UUID battleGroupId;
#Column(name = "player_id")
private Integer playerId;
#Column(name = "village_id")
private Integer villageId;
public BattleGroupVillageId(UUID battleGroupId, Integer playerId, Integer villageId) {
this.battleGroupId = battleGroupId;
this.villageId = villageId;
this.playerId = playerId;
}
}
Now, Serializable needs to be implemented in every class as we have used #EmbeddedId which requires the container class to be Serializable as well, hence every parent class must implement serializable, otherwise it would give error.
Now, we can solve the problem using #JoinColumn annotation like below:
#OneToMany(cascade = CasacadeType.ALL, fetch =EAGER)
#JoinColumn(name = "player_id", referencedColumnName = "player_id")
private List<BattleGroupVillage> villages = new ArrayList<>();
name -> field in child table and referenceColumnName -> field in parent table.
This will join the column player_id column in both entities.
SELECT
battlegrou0_.id AS id1_0_0_,
battlegrou0_.name AS name2_0_0_,
players1_.battle_group_id AS battle_g2_1_1_,
players1_.id AS id1_1_1_,
players1_.id AS id1_1_2_,
players1_.battle_group_id AS battle_g2_1_2_,
players1_.player_id AS player_i3_1_2_,
villages2_.player_id AS player_i4_2_3_,
villages2_.battle_group_id AS battle_g1_2_3_,
villages2_.village_id AS village_2_2_3_,
villages2_.battle_group_id AS battle_g1_2_4_,
villages2_.player_id AS player_i4_2_4_,
villages2_.village_id AS village_2_2_4_,
villages2_.name AS name3_2_4_
FROM
battle_group battlegrou0_
LEFT OUTER JOIN
battle_group_player players1_ ON battlegrou0_.id = players1_.battle_group_id
LEFT OUTER JOIN
battle_group_village villages2_ ON players1_.player_id = villages2_.player_id
WHERE
battlegrou0_.id = 1;
But this would give 2 players if you check the BattleGroup#getPlayers() method, below is the test case to verify.
UUID battleGroupId = UUID.randomUUID();
doInTransaction( em -> {
BattleGroupPlayer player = new BattleGroupPlayer(UUID.randomUUID(), battleGroupId, 1);
BattleGroupVillageId villageId1 = new BattleGroupVillageId(
battleGroupId,
1,
1
);
BattleGroupVillageId villageId2 = new BattleGroupVillageId(
battleGroupId,
1,
2
);
BattleGroupVillage village1 = new BattleGroupVillage(villageId1, "Village 1");
BattleGroupVillage village2 = new BattleGroupVillage(villageId2, "Village 2");
player.addVillage(village1);
player.addVillage(village2);
BattleGroup battleGroup = new BattleGroup(battleGroupId, "Takeshi Castle");
battleGroup.addPlayer(player);
em.persist(battleGroup);
});
doInTransaction( em -> {
BattleGroup battleGroup = em.find(BattleGroup.class, battleGroupId);
assertNotNull(battleGroup);
assertEquals(2, battleGroup.getPlayers().size());
BattleGroupPlayer player = battleGroup.getPlayers().get(0);
assertEquals(2, player.getVillages().size());
});
If your use case was to get the single player from BattleGroup then you would have to use FETCH.LAZY, which is btw good for performance as well.
Why LAZY works?
Because LAZY loading will issue separate select statement when you really access them. EAGER will load whole graph, wherever you have it. It means, it will try to load all relationship mapped with this type, hence it will perform outer join (which may result in 2 rows for players as your criteria is unique because of villageId, which you cannot know before querying).
If you have more than 1 such fields i.e want join on battleGroupId as well, you would need this
#JoinColumns({
#JoinColumn(name = "player_id", referencedColumnName = "player_id"),
#JoinColumn(name = "battle_group_id", referencedColumnName = "battle_group_id")
}
)
NOTE: Used h2 in memory db for test case
I am trying to fetch with one query list of objects and its associations, unfortuantely, either I cause N+1 requests to database, or get hit with exception "org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list".
Please let me walk you through my case.
Below is my Data Model:
#Table(name = "first_table")
public class FirstObject {
#Id
#Column(nullable = false, name = "first_id")
private Long id;
#Column(nullable = false, name = "first_param")
private String param1;
#ManyToOne
#JoinColumn(nullable = false, name = "second_id")
private SecondObject second;
...other columns...
}
#Table(name = "second_table")
public class SecondObject {
#Id
#Column(nullable = false, name = "second_id")
private Long id;
#Column(nullable = false, name = "second_param")
private Long param2;
#ManyToOne
#JoinColumn(nullable = false, name = "third_id")
private ThirdObject third;
...other columns...
}
#Table(name = "third_table")
public class ThirdObject {
#Id
#Column(nullable = false, name = "third_id")
private Long id;
...other columns...
}
It is true to database relations, also exactly how I want it on FE.
All I am trying to achieve is to fetch all the associations with one query, giving 2 conditions:
ConditionBuilder condition = new ConditionBuilder()
.and(FirstObject.second.param2.eq(some_number))
.and(FirstObject.param1.eq(some_string));
return from(FirstObject)
.join(FirstObject.second).fetchJoin()
.join(FirstObject.second.third).fetchJoin()
.where(condition.generate())
.fetch();
Unfortunately this code throws exception:
org.hibernate.QueryException: query specified join fetching, but the
owner of the fetched association was not present in the select list
I can make it work, but with N+1 queries, but it is acceptable only for development phase, as will cause performance issue.
...
.join(FirstObject.second).fetchJoin()
.join(FirstObject.second.third)
...
same here:
...
.join(FirstObject.second)
.join(FirstObject.second.third)
...
What I am trying to figure out is how to make hibernate to create one simple query like that:
select
*
from
first_table table1
inner join
second_table table2
on table1.second_id=table2.second_id
inner join
third_table table3
on table2.third_id=table3.third_id
where
table1.first_param="some_string"
table2.second_param=some_number
All the help is very much appreciated, I've been fighting this for some time now, and really counting on community. Thank you very much.
You should be mapping both sides of the entity relationship:
for instance, in FirstObject you have this:
#ManyToOne
#JoinColumn(nullable = false, name = "second_id")
private SecondObject second;
So in SecondObject you should have this:
#OneToMany(mappedBy = "second") // this is the name of the field in the class that defines the join relationship
Collection<FirstObject> firstObjects;
In ThirdObject you should have this:
#OneToMany(mappedBy = "third") // this is the name of the field in the class that defines the join relationship
Collection<SecondObject> secondObjects;
I am trying to get the last EmergencyJob carried out by each Employee (i.e. the one with the max endTime).
I have the following entities
EmergencyJob
#Entity
#Table(name = "emergencyjobs", schema = "simulator")
public class EmergencyJob {
#Id
private String jobId;
private LocalDate dateLogged;
private LocalTime timeLogged;
private double easting;
private double northing;
private String priority;
private Point location;
#ManyToOne
private Engineer assignedEngineer;
private LocalTime startTime;
private LocalTime endTime;
...
}
Engineer
#Entity
#Table(name = "engineer", schema = "simulator")
public class Engineer {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private int engineerId;
private Point homeLocation;
...
}
With the tables are generated by Hibernate I can do what I need in the database using the following query:
SELECT e.*
FROM simulator.emergencyjobs AS e
INNER JOIN (
SELECT
assigned_engineer_engineer_id,
max(end_time) as end_time
FROM simulator.emergencyjobs
GROUP BY assigned_engineer_engineer_id
) AS ee
ON e.assigned_engineer_engineer_id = ee.assigned_engineer_engineer_id
AND e.end_time = ee.end_time
But I can't figure out how to use this to retrieve a list of EmergencyJob entities in Hibernate.
Any help would be appreciated!
This should do the trick (fetch is optional):
select ej
from emergencyJob ej
inner join fetch ej.assignedEngineer e
where ej.endTime = (select max(distinct sej.endTime)
from emergencyJob sej
where sej.assignedEngineer = e)
Also remember to define the join column on EmergencyJob entity:
#ManyToOne
#JoinColumn(name = "assigned_engineer_engineer_id")
private Engineer assignedEngineer;
Help me plz with one moment. I read about 10 articles already, but don't understand join moment. I have 2 tables:
public class News implements Serializable {
#Id
#GeneratedValue (generator = "increment")
#GenericGenerator (name = "increment", strategy = "increment")
private int id;
#Column
private String name;
#Column
private Date created;
#Column
private String data;
#ManyToOne (cascade = CascadeType.ALL, fetch = FetchType.LAZY)
#JoinColumn (name = "category_id")
private NewsCategoryDict category;
// getters, setters
}
and
public class NewsCategoryDict implements Serializable {
#Id
#GeneratedValue (generator = "increment")
#GenericGenerator (name = "increment", strategy = "increment")
private int id;
#Column
private String name;
#OneToMany (mappedBy = "category", cascade = CascadeType.ALL)
private List<News> news = new ArrayList<>();
}
I want a query works like
SELECT * FROM news, categorynews WHERE news.category_id = categorynews.id;
And then get the result in jsp with
<div id="list_news">
<c:forEach items="${news}" var="news">
<h5>${news.id} : ${news.name} - ${news.created} ; ${news.data} (${news.category.name})</h5>
</c:forEach>
</div>
And I just can't understand this JOIN with Criteria API. Can you help me ?
Try to use this snippet, but get a error
public List<News> getAll() {
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<News> cq = cb.createQuery(News.class);
Root<News> rootFromNews = cq.from(News.class);
Join<NewsCategoryDict, News> join = rootFromNews.join("category");
cq.select(join);
return em.createQuery(cq).getResultList();
}
PropertyNotFoundException: Property 'created' not found on type ru.r1k0.spring.model.NewsCategoryDict
Assuming you want to return an instance of News associated to an instance of NewsCategoryDict, your criteria query should look as follows:
public List<News> getAll() {
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<News> cq = cb.createQuery(News.class);
Root<News> rootFromNews = cq.from(News.class);
Join<News, NewsCategoryDict> join = rootFromNews.join("category"); // #1
cq.select(rootFromNews); // #2
return em.createQuery(cq).getResultList();
}
The modified lines are marked with #1 and #2 comments.
The query should return all News which have a matching NewsCategoryDict; but News records which are not associated to aNewsCategoryDict record will not be returned.
Your error has nothing to do with the join! What is actually happening is that in the JSP fragment you are trying to access ${news.created} which does not exist in the NewsCategoryDict. I believe the error is in the JSP fragment, not in the Criteria query.
The way I understand it is that you want to list the News object, but in the query you are selecting the NewsCategoryDict and this is why at the end you end up with missing attribute because the NewsCategoryDict does not contain ${news.created}
Learning how to write JPA query. Please advise me whether it possible to write the below queries more efficiently, may be in a single select statement. May be a join, but not sure how to do it.
class Relationship {
#ManyToOne
public String relationshipType; //can be MANAGER, CUSTOMER etc
#ManyToOne
public Party partyFrom; // a person who has a relation
#ManyToOne
public Party partyTo; // a group a person relate to
}
Queries:
String sql = "";
sql = "select rel.partyTo";
sql += " from Relationship rel";
sql += " where rel.partyFrom = :partyFrom";
sql += " and rel.relationshipType= :typeName";
Query query = Organization.em().createQuery(sql);
query.setParameter("partyFrom", mgr1);
query.setParameter("typeName", "MANAGER");
List<Party> orgList = query.getResultList();
String sql2 = "";
sql2 = "select rel.partyFrom";
sql2 += " from Relationship rel";
sql2 += " where rel.partyTo = :partyToList";
sql2 += " and rel.relationshipType = :typeName2";
Query query2 = Organization.em().createQuery(sql2);
query2.setParameter("partyToList", orgList);
query2.setParameter("typeName2", "CUSTOMER");
List<Party> personList2 = query2.getResultList();
Both the queries work. Query 1 returns a list of groups, where the person (mgr1) has a relation MANAGER with. Query 2 returns all the Persons they are CUSTOMER to the groups returned by query 1. In effect, I get a list of Person they are belong to (customer) the same group where the Person (mgr1) has a relation MANAGER with.
Is it possible to combine them into single sql statement so possibly only one db access?
You literally nest one query inside the other, and use a "where in" clause to specify that the outer query should fetch customers from the inner query.
select rel2.partyFrom
from Relationship rel2
where rel2.relationshipType = :typeName2 /* customer */
and rel2.partyTo.id in
(select rel.partyTo.id
from Relationship rel
where rel.partyFrom = :partyFrom
and rel.relationshipType = :typeName)
Your calling code passes typeName, typeName2, and partyFrom parameters as before. PartyTo parameter is not needed, since the data comes from the subselect (inner query.)
You can achieve the same thing using a self join, with a where clause that filters managers on the left side, and customers on the right side, but using an 'in' clause is semantically clearer.
EDIT: I addded .id to the subselect, which I think is needed.
This is not answer to question but helping other folks in case if someone looking into #OneToMany relation in Spring Data JPA using JPQL, because the question is related to JPA so thought to share my 2-cents, apologize in advance
#Entity
#Table(name = "MY_CAR")
public class MyCar {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name = "DESCRIPTION")
private String description;
#Column(name = "MY_CAR_NUMBER")
private String myCarNumber;
#Column(name = "RELEASE_DATE")
private Date releaseDate;
#OneToMany(cascade = { CascadeType.ALL })
#JoinTable(name = "MY_CAR_VEHICLE_SERIES", joinColumns = #JoinColumn(name = "MY_CAR_ID "), inverseJoinColumns = #JoinColumn(name = "VEHICLE_SERIES_ID"))
private Set<VehicleSeries> vehicleSeries;
public MyCar() {
super();
vehicleSeries = new HashSet<VehicleSeries>();
}
// set and get method goes here
#Entity
#Table(name = "VEHICLE_SERIES ")
public class VehicleSeries {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name = "SERIES_NUMBER")
private String seriesNumber;
#OneToMany(cascade = { CascadeType.ALL })
#JoinTable(name = "VEHICLE_SERIES_BODY_TYPE", joinColumns = #JoinColumn(name = "VEHICLE_SERIES_ID"), inverseJoinColumns = #JoinColumn(name = "BODY_TYPE_ID"))
private Set<BodyType> bodyTypes;
public VehicleSeries() {
super();
bodyTypes = new HashSet<BodyType>();
}
// set and get method goes here
#Entity
#Table(name = "BODY_TYPE ")
public class BodyType implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name = "NAME")
private String name;
// set and get method goes here
public interface MyCarRepository extends JpaRepository<MyCar, Long> {
public Set<MyCar> findAllByOrderByIdAsc();
#Query(value = "select distinct myCar from MyCar myCar "
+ "join myCar.vehicleSeries as vs join vs.bodyTypes as bt where vs.seriesNumber like %:searchMyCar% "
+ "or lower(bt.name) like lower(:searchMyCar) or myCar.bulletinId like %:searchMyCar% "
+ "or lower(myCar.description) like lower(:searchMyCar) "
+ "or myCar.bulletinNumber like %:searchMyCar% order by myCar.id asc")
public Set<MyCar> searchByMyCar(#Param("searchMyCar") String searchMyCar);
}
Some data in tables like
Select * from Vehicle_Series
ID SERIES_NUMBER
1 Yaris
2 Corolla
Select * from Body_Type
ID NAME
1 Compact
2 Convertible
3 Sedan