Is it possible to join two entity cross schema with JPA.
Example:
#Entity
#Table(schema="department")
public class Department{
#Id
Integer departmentId;
String departmentName;
}
#Entity
#Table(schema="student")
public class Student{
#Id
Integer studentId;
String studentName;
#OneToOne
#MapsId("departmentId")
#JoinColumn(name = "departmentId")
Department department;
}
Please advise me how can I do that.
Thank you!
Related
I have a couple of related entities in a relational DB:
#Entity
public class A {
#Id
#Column(name = "id" ...)
private UUID id;
#OneToMany(mappedBy = "a")
private Set<B> bs;
}
and
#Entity
public class B {
#Id
#Column(name = "id" ...)
private UUID id;
#ManyToOne
#JoinColumn(name = "a_id")
private A a;
}
So I have a B Repository
#Repository
public interface BRepository extends JpaRepository<B, UUID> {
List<B> findByA(A a);
}
And id like to have a query by which I obtain the all Bs with the same A. I'm used to have an a_id column in B, not the whole entity. I don't know how to manage this, nor with a JPA query nor with a NamedQuery.
Many thanks in advance!
Luis
As already answered, the proposed code should already work but it didn't... The fix that worked for me was
List<B> findByA_Id(UUID id);
Table_Field references field field to table Table.
I'm trying to have Spring Data JPA issue one query using joins to eagerly get a graph of entities:
#Entity
#NamedEntityGraph(name = "PositionKey.all",
attributeNodes = {#NamedAttributeNode("positionKey.account"),
#NamedAttributeNode("positionKey.product")
})
#Data
public class Position {
#EmbeddedId
private PositionKey positionKey;
}
#Embeddable
#Data
public class PositionKey implements Serializable {
#ManyToOne
#JoinColumn(name = "accountId")
private Account account;
#ManyToOne
#JoinColumn(name = "productId")
private Product product;
}
Here's my Spring Data repo:
public interface PositionRepository extends JpaRepository<Position, PositionKey> {
#EntityGraph(value = "PositionKey.all", type = EntityGraphType.LOAD)
List<Position> findByPositionKeyAccountIn(Set<Account> accounts);
}
This produces the following exception:
java.lang.IllegalArgumentException: Unable to locate Attribute with the the given name [positionKey.account] on this ManagedType
I want all of the accounts and products to be retrieved in one join statement with the positions. How can I do this / reference the embedded ID properties?
I would suggest refactoring the entity this way if it possible
#Entity
#NamedEntityGraph(name = "PositionKey.all",
attributeNodes = {#NamedAttributeNode("account"),
#NamedAttributeNode("product")
})
#Data
public class Position {
#EmbeddedId
private PositionKey positionKey;
#MapsId("accountId")
#ManyToOne
#JoinColumn(name = "accountId")
private Account account;
#MapsId("productId")
#ManyToOne
#JoinColumn(name = "productId")
private Product product;
}
#Embeddable
#Data
public class PositionKey implements Serializable {
#Column(name = "accountId")
private Long accountId;
#Column(name = "productId")
private Long productId;
}
Such an EmbeddedId is much easier to use. For instance, when you are trying to get an entity by id, you do not need to create a complex key containing two entities.
I have a table structure like this
Good Assignments Entity
#Embeddable
public class GoodAssignmentId {
String clientId,
String assignmentNumber;
LocalDate effectiveDate;
// Getters and setters
}
#Entity
#IdClass(GoodAssignmentId.class)
class GoodAssignment {
#id
String clientId;
#Id
String assignmentNumber;
#Id
LocalDate effectiveDate;
#OneToMany(mappedBy = "parentKey")
Set<GoodTasks> children;
String description;
// getters and setters goes below
}
Bad Assignments Entity
#Entity
#IdClass(BadAssignmentId.class)
class BadAssignment {
#id
String clientId;
#Id
String assignementNumber;
#Id
LocalDate effectiveDate;
String description;
// Getters and setters goes below
}
Child entities
#Entity
#IdClass(ParentTasksId.class)
#DiscriminatorColumn(name = "fieldD", discriminatorType = DiscriminatorType.STRING)
class ParentTasks {
#Id
String clientId;
#Id
String assignmentNumber;
#Id
String taskNumber;
}
#Entity
#DiscriminatorValue("G")
class GoodTasks extends ParentTasks {
#ManyToOne
#JoinColumns({
#JoinColumn(name = "clientId", referencedColumName = "clientId"),
#JoinColumn(name = "assignmentNumber", referencedColumName = "assignmentNumber")
})
GoodAssignments parentKey;
other fields....
}
This shows the error referencedColumnNames(fieldA, fieldB) of .... not mapped to a single property.
Unfortunately I cannot change the table structure. TableA has 3 columns as primary key, but only two of them forms the primary key in table B along with another field (fieldD via #DiscriminatorValue used by multiple classes). How can I map this relationship to get list of TableB items in TableA?
Example Class Diagram:
Effective date in the assignments tables is not part of tasks. So this is not a perfect relationship in JPA terms. It's a legacy design which cannot be changed for some reasons.
I had entities User, BlockUnit, Block and Unit as Follows.
User has ManyToMany relation with blockunit.
#Entity
public class User {
#ManyToMany
private Set<BlockUnit> blockUnits;
}
#Entity
public class BlockUnit {
#Id
private Long id;
#OneToOne(targetEntity = Block.class)
#JoinColumn(name = "block_id")
private Block block;
#OneToOne(targetEntity = Unit.class)
#JoinColumn(name = "unit_id")
private Unit unit;
#ManyToMany(fetch = FetchType.LAZY)
private Set<User> users = new HashSet<>();
}
BlockUnit has OneToOne relation with Block and Unit.
#Entity
public class Block {
#Id
private Long id;
}
#Entity
public class Unit {
#Id
private Long id;
}
How should I create the JPA criteria specification for above in order to select user's having Block ID and Unit ID?
Thank you very much in advance!
i have first entity :
#Entity
#Table(name="TABLE_ONE")
public class TableOne implements Serializable {
#Id
#Column(name="ID")
private Integer id;
#ManyToOne
#JoinColumn(name="TABLE_TWO_ID", nullable = false)
private TableTwo tableTwoId;
and the second table entity :
#Entity
#Table(name="TABLE_TWO")
public class TableTwo{
#Id
#Column(name="ID")
private Integer id;
, but then after i compile , the result is :
ERROR: column "table_two_id" does not exist
I want to get ID from TableTwo.
Joincolumn annotation tells hibernate the foreign key join column name, in this case I guess it's ID.