I have an entity, that i'd like to join OneToOne with a table with a composite key (Omitting getters/setters):
#Entity
#Table(name = "parent")
public class Parent {
#Id
private String parentId;
#Column(name = "data")
private String data;
#OneToOne
private Child child;
}
And:
#Entity
#IdClass(ChildKey.class)
#Table(name = "child")
public class Child{
#Id
private String parentId;
#Id
private String username;
#Column(name = "data")
private String childData;
}
public class ChildKey implements Serializable {
private String parentId;
private String username;
}
Parent does not have a notion of the 'username' field in the Child entity. I need to pass this in as criteria. In the DB, the primary key of child is on parentId and username.
If I don't specify a JoinColumn, hibernate attempts to map using fields child_username and child_parentId. If I specify only one Joincolumn, I get a broken mapping. If I specify both JoinColumns, I have no column on parent to specify.
How can I map this class and pass in the username as criteria? (it is coming from authentication data) Or how can I do this in a different way if I'm off track.
You might be able to use a Derived Identity.
The Parent class would remain the same; but you would specify a #OneToOne mapping back to the child's parent and the Child and ChildKey classes would look like this:
#Entity
#IdClass(ChildKey.class)
#Table(name = "child")
public class Child{
#Id
#OneToOne(mappedBy="child")
private Parent parent;
#Id
private String username;
#Column(name = "data")
private String childData;
}
public class ChildKey implements Serializable {
private String parent; // name matches name of the #Id field and type matches type of Parent #Id field
private String username; // name and type match those of the #Id field
}
Derived identity is discussed in JPA 2.1 spec, section 2.4.1.
What I ended up doing was defining a #Filter on the Child class, like so:
#Entity
#IdClass(ChildKey.class)
#Table(name = "child")
#FilterDef(name = "usernameFilter", parameters = {
#ParamDef( name = "username", type="string")
})
public class Child { ... }
On the Parent class, I annotated the collection with a reference to the filter:
#OneToMany(fetch = FetchType.EAGER)
#JoinColumn(name = "parentId")
#Filter(name="usernameFilter", condition = "username = :username")
private List<Child> children;
Finally, in my DAO, I parameterized the filter by name like so:
Filter filter = currentSession().enableFilter("usernameFilter");
filter.setParameter("username", user.getUsername());
Doing this resulted in the exact SQL I had in mind, which is an additional clause in the JOIN criteria with a variable:
SELECT
...
FROM
parent this_
LEFT OUTER JOIN
child child_ ON this_.parentId = child_.parentId
AND child_.username = ?
I might not have been clear about what end result I was looking for in my original question. Posting this answer in case it helps someone else.
Related
I have a doubt about how the modeling of my entity would be. Come on, I have a table in the database that serves to save documents from my system, this table has the columns id, fk_id (element foreign key), fk_table (entity name) and file_name (stores the name of my file) .
I did a lot of research before posting my question here, but I didn't find anything related to it, what would my entities, user, patient and doctor?
DB:
id
fk_id
fk_table
file_name
1
21
user
test1.jpg
2
32
doctor
test2.pdf
3
61
user
test10.pdf
4
100
patient
test5.jpg
Class:
public class User{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String firstName;
private String LastName;
// What would a one-to-many relationship look like?
}
public class patient{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String firstName;
private String lastName;
// What would a one-to-many relationship look like?
}
You can use #Where. But be aware that #Where is a Hibernate annotation. It's not in the JPA standard.
For example in the User entity: (I assume that your table is mapped to an entity called Document)
#Where( clause = "fk_table = 'user'")
#JoinColumn(name = "fk_id")
#OneToMany
private List<Document> documents = new ArrayList<>( );
The following is based only on standard JPA annotations. The idea is to create an inheritance hierarchy for the documents table. The base is:
#Entity
#Table(name = "XX_DOCUMENT")
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorColumn(name = "fk_table")
public abstract class BaseDocument {
#Id
#GeneratedValue(strategy=SEQUENCE)
private Long id;
#Column(name = "file_name")
private String fileName;
}
Here we define that all entities extending this will go to the same table, with the fk_table column to discriminate. The entities extending it are defined as follows:
#Entity
#DiscriminatorValue("doctor")
public class DoctorDocument extends BaseDocument {
#ManyToOne
#JoinColumn(name = "fk_id")
private Doctor doctor;
}
#Entity
#DiscriminatorValue("patient")
public class PatientDocument extends BaseDocument {
#ManyToOne
#JoinColumn(name = "fk_id")
private Patient patient;
}
// and so on
The interesting thing is that we are reusing the column fk_id to point to the right table. From a small experiment, Hibernate seems to not have problems with it. I would suggest that you manage the DB creation another way just to be safe.
The Doctor, Patient etc need not have a common base class, e.g.:
#Entity
#Table(name = "XX_DOCTOR")
public class Doctor {
#Id
#GeneratedValue(strategy=SEQUENCE)
private Long id;
#OneToMany(mappedBy = "doctor")
private Collection<DoctorDocument> documents = new ArrayList<>();
// any doctor-specific fields
}
#Entity
#Table(name = "XX_PATIENT")
public class Patient {
#Id
#GeneratedValue(strategy=SEQUENCE)
private Long id;
#OneToMany(mappedBy = "patient")
private Collection<PatientDocument> documents = new ArrayList<>();
// any patient-specific fields
}
// and so on
You can read a (doctor, patient, ...)'s documents from the relevant collection. You can even query BaseDocument instances based on any criteria.
You can even go ahead and do more fabcy stuff with the Java code. E.g. define an interface HasDocuments:
public interface HasDocuments<D extends BaseDocument> {
Collection<D> getDocuments();
}
Doctor, Patient, ..., implements this, so they can all be treated the same way.
I have main entity:
#Entity
#Table(name = "partners")
public class Partner {
#ElementCollection
#CollectionTable(
name = "external_login",
joinColumns = #JoinColumn(name = "partner_id")
)
private List<ExternalLogin> externalLogins;
...
}
And ExternalLogin is embeded entity
#Embeddable
public class ExternalLogin {
#Column(name = "type")
#Enumerated(value = EnumType.STRING)
private ExternalLoginType type;
#Column(name = "login")
private String login;
#Column(name = "password_value")
private String passwordValue;
}
public enum ExternalLoginType {
ABC;
}
#Column and #Enumerated not works in ExternalLogin entity.
For example in query will be external_login.passwordValue instead of external_login.password_value.
#Enumerated(value = EnumType.STRING) doesn't work too. Hibernate is trying to get int value of filed instead string.
Can anyone help me?
You misuse annotation #Embeddable. See description in oracle docs https://docs.oracle.com/javaee/6/api/javax/persistence/Embeddable.html
Defines a class whose instances are stored as an intrinsic part of an owning entity and share the identity of the entity. Each of the persistent properties or fields of the embedded object is mapped to the database table for the entit
#Embeddable annotation makes sense only for singular assotiation fields. Annotating list fields as #Embeddable is wrong.
Just replace
#Embeddable
public class ExternalLogin {
to
#Entity
public class ExternalLogin {
I had exactly the same issue just now.
The solution for me ended up being adding
#Access(FIELD)
To the Embeddable object.
How i can add based and descendant class in one table with Hibernate?
Based class
public class Id{
protected int id
}
Descendant class
public classs User exetends Id{
public String username;
public String password;
}
In one table USERS with properties: id, username, password.
From what i understood.
You want to have a Base entity. And that Base entity should be extended by other Descendant entities. In other words the Descendant should be having all the properties from the Base entity. One use case for this design is to have common properties(id, createdDate, updatedDate) for all Descendant class in a Base entity class.
One way to go with this is:
BaseEntity(Base Class)
#MappedSuperclass
public class BaseEntity {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
//..setter and getters
}
User(Descendant Class)
#Entity
#Table(name = "user")
public class User extends BaseEntity {
#Column(name = "name")
private String name; //User specific properties
//..setters and getters here
}
Firstly you need to mark them with #Entity to show that they are tables, then in the top level set the table name with #Table. To use inheritance, you need to select a strategy: for this instance you want SINGLE_TABLE. Then in order to select the correct type a #DiscriminatorColumn is required, setting the column name and the type of discriminator - in this case I have chosen INTEGER. You'll need to also add to the type annotation updatable = false and insertable = false so they cannot be modified.
#Entity
#Table(name = "TABLE_NAME")
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorColumn(name = "TYPE",discriminatorType = DiscriminatorType.INTEGER)
public class Id {
#Column(name="TYPE", insertable=false, updatable=false)
private Integer type;
}
On your sub classes you need to mark them with #Entity and a #DiscriminatorValue (in this case 1).
#Entity
#DiscriminatorValue(value = "1")
public classs User exetends Id{
public String username;
public String password;
}
I am designing two entities, one called Country and one called CountryDetail. From the perspective of tables, the COUNTRY table will be the parent table, and the COUNTRY_DETAIL table will be the child table. In the COUNTRY table, there will be a unique attribute called COUNTRY_CODE (note this is not a primary key; the primary key will be a numeric sequence based value). This code will be a foreign key to connect to the child table, and in this child table, each COUNTRY_CODE from the parent table will have 3 entries to represent the name of the country in 3 different languages. Following are the entity classes:
Country.java
#Entity
public class Country
{
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "COUNTRY_ID")
private long id;
#Column(name="COUNTRY_CODE", nullable = false, unique = true)
private String countryCode;
/*public getters*/
}
CountryDetail.java
#Entity
public class CountryDetail
{
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "COUNTRY_DETAIL_ID")
private long id;
#ManyToOne
#JoinColumn(name="COUNTRY_CODE", referencedColumnName = "COUNTRY_CODE")
private Country country;
#Column(nullable = false)
private String languageCode;
#Column(nullable = false, unique = true)
private String countryNameInLanguage;
/*public getters*/
}
My question is, how can I write a custom "findBy..." interface method inside an extension of JpaRepository that is typed to a Country that would return me a collection of CountryDetail elements that match an input parameter for the languageCode attribute of the CountryDetail class?
public interface CountryRepository extends JpaRepository<Country, Long>
I know how to do it if the repository was typed to CountryDetail instead of Country, but I would like to know how to do it going via the parent entity rather than via the child entity directly, even though the input parameter (languageCode) exists only in the child entity.
Thank you.
It is possible but complicated : Please see an example below :
Parent :
#Entity
#Table(name="PARENT")
public class Parent {
#Id
#Column(name="PARENT_ID")
private int parentId;
#Column(name="PARENT_NAME")
private String parentName;
#OneToOne(cascade=CascadeType.ALL,fetch=FetchType.EAGER)
private Child child;
}
Child :
#Entity
#Table(name="CHILD")
public class Child {
#Id
#Column(name="CHILD_ID")
private int childId;
#Column(name="CHILD_NAME")
private String childName;
#OneToOne(cascade=CascadeType.ALL,fetch=FetchType.EAGER)
private Parent parent;
}
Define an interface to load child entity from parent repository :
ChildEntity:
public interface ChildEntity {
#Value("#{target.child.childId}")
int getChildId() ;
#Value("#{target.child.childName}")
String getChildName();
}
Parent Repository :
public interface ParentRepository extends JpaRepository<Parent, Integer> {
public ChildEntity findByParentName(String parentName);
}
Test class:
ChildEntity chi=rep.findByParentName("<<NAME>>");
System.out.println(chi.getChildId()+" "+chi.getChildName());
Output:
CHILD ID 1000 CHILD NAME child1
I've ran into problem with composite primary key handling by Hibernate as a JPA provider.
My entities look like below
// Entity class
#Entity
#IdClass(ExternalMatchPK.class)
#Table(name = "external_match")
public class ExternalMatch {
#Id
#Column(name = "place_id")
private Integer placeId;
#Id
#Column(name = "external_object_id")
private Integer externalObjectId;
// ... Other stuff here
}
// Key class
public class ExternalMatchPK implements Serializable {
private Integer placeId;
private Integer externalObjectId;
}
Looks pretty simple yet no matter what I do I keep getting the following exception (lines are splitted for readability):
org.hibernate.MappingException:
Repeated column in mapping for entity: ExternalMatch
column: external_object_id (should be mapped with insert="false" update="false")
I've tried placing annotation on entity class fields and key class fields together as well as separately, moving all annotations from fields to getters on each one of the classes, using key calss as #Embeddable and putting it into the entity class with #EmbeddedId. Nothing seems to work.
This case seems trivial so maybe it's something wrong with our setup but I can't even imagine where to look for the issue.
Any advice is much appreciated.
It appears that I shot myself in the foot with this.
The issue was that I had a biderectional mapping between ExternalMatch and ExternalObject I forgot about trying to replace the actual entity with its integer id.
So changing
// Entity class
#Entity
#IdClass(ExternalMatchPK.class)
#Table(name = "external_match")
public class ExternalMatch {
#Id
#Column(name = "place_id")
private Integer placeId;
#Id
#Column(name = "external_object_id")
private Integer externalObjectId;
// ... Other stuff here
}
// Key class
public class ExternalMatchPK implements Serializable {
private Integer placeId;
private Integer externalObjectId;
}
// Related entity class
#Entity
#Table(name = "external_object")
public class ExternalObject extends AbstractNameableEntity {
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
#JoinColumn(name = "external_object_id", nullable = false)
private List<ExternalMatch> matches;
// ...
}
to reprsent actual mappings like this
// Entity class
#Entity
#IdClass(ExternalMatchPK.class)
#Table(name = "external_match")
public class ExternalMatch {
#Id
#ManyToOne
#JoinColumn(name = "external_object_id", referencedColumnName = "id")
private ExternalObject externalObject;
#Id
#ManyToOne
#JoinColumn(name = "place_id")
private Poi place;
// ... Other stuff here
}
// Key class
public class ExternalMatchPK implements Serializable {
private Poi place;
private ExternalObject externalObject;
}
// Related entity class
#Entity
#Table(name = "external_object")
public class ExternalObject extends AbstractNameableEntity {
#OneToMany(cascade = CascadeType.ALL, mappedBy = "externalObject")
private List<ExternalMatch> matches;
// ...
}
resolved the repeated mapping issue yet leaving us with all the familiar troubles a biderectional mapping creates :)