@ManyToOne
Creates a child, parent association with a foreign key in child.
@Entity(name = "Person")
public static class Person {
@Id
@GeneratedValue
private Long id;
}
@Entity(name = "Phone")
public static class Phone {
@Id
@GeneratedValue
private Long id;
@Column(name = "`number`")
private String number;
@ManyToOne
@JoinColumn(name = "person_id",
foreignKey = @ForeignKey(name = "PERSON_ID_FK")
)
private Person person;
}@OneToMany
Created an association between an parent and one or more child entities. It can be bidirectional by using an @ManyToOne declaration in the child.
Unidirectional
In a unidirectional association a link table will be used to join both entities.
@Entity(name = "Person")
public static class Person {
@Id
@GeneratedValue
private Long id;
@OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
private List<Phone> phones = new ArrayList<>();
}
@Entity(name = "Phone")
public static class Phone {
@Id
@GeneratedValue
private Long id;
@Column(name = "`number`")
private String number;
}Bidirectional
The bidirectional association requires a @ManyToOne association on the child side, only a foreign key in child is used, the developer must ensure synchronization between the parties.
@Entity(name = "Person")
public static class Person {
@Id
@GeneratedValue
private Long id;
@OneToMany(mappedBy = "person", cascade = CascadeType.ALL, orphanRemoval = true)
private List<Phone> phones = new ArrayList<>();
public void addPhone(Phone phone) {
phones.add(phone);
phone.setPerson(this);
}
public void removePhone(Phone phone) {
phones.remove(phone);
phone.setPerson(null);
}
}
@Entity(name = "Phone")
public static class Phone {
@Id
@GeneratedValue
private Long id;
@NaturalId
@Column(name = "`number`", unique = true)
private String number;
@ManyToOne
private Person person;
}@OneToOne
Relation between a parent and a child, can be unidirectional or bidirectional.
Unidirectional
The parent will have a foreign key from the child, unusual solution.
@Entity(name = "Phone")
public static class Phone {
@Id
@GeneratedValue
private Long id;
@Column(name = "`number`")
private String number;
@OneToOne
@JoinColumn(name = "details_id")
private PhoneDetails details;
}
@Entity(name = "PhoneDetails")
public static class PhoneDetails {
@Id
@GeneratedValue
private Long id;
private String provider;
private String technology;
}Bidirectional
Creates foreign key in child.
@Entity(name = "Phone")
public static class Phone {
@Id
@GeneratedValue
private Long id;
@Column(name = "`number`")
private String number;
@OneToOne(
mappedBy = "phone",
cascade = CascadeType.ALL,
orphanRemoval = true,
fetch = FetchType.LAZY
)
private PhoneDetails details;
public void addDetails(PhoneDetails details) {
details.setPhone(this);
this.details = details;
}
public void removeDetails() {
if (details != null) {
details.setPhone(null);
this.details = null;
}
}
}
@Entity(name = "PhoneDetails")
public static class PhoneDetails {
@Id
@GeneratedValue
private Long id;
private String provider;
private String technology;
@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "phone_id")
private Phone phone;
}@ManyToMany
Creates associations by the use of a link table, it can unidirectional or bidirectional.
Unidirectional
Child had no reference for father.
@Entity(name = "Person")
public static class Person {
@Id
@GeneratedValue
private Long id;
@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
private List<Address> addresses = new ArrayList<>();
}
@Entity(name = "Address")
public static class Address {
@Id
@GeneratedValue
private Long id;
private String street;
@Column(name = "`number`")
private String number;
}Bidirectional
@Entity(name = "Person")
public static class Person {
@Id
@GeneratedValue
private Long id;
@NaturalId
private String registrationNumber;
@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
private List<Address> addresses = new ArrayList<>();
//Getters and setters are omitted for brevity
public void addAddress(Address address) {
addresses.add(address);
address.getOwners().add(this);
}
public void removeAddress(Address address) {
addresses.remove(address);
address.getOwners().remove(this);
}
}
@Entity(name = "Address")
public static class Address {
@Id
@GeneratedValue
private Long id;
private String street;
@Column(name = "`number`")
private String number;
private String postalCode;
@ManyToMany(mappedBy = "addresses")
private List<Person> owners = new ArrayList<>();
}Bidirectional
@Entity(name = "Person")
public static class Person {
@Id
@GeneratedValue
private Long id;
@NaturalId
private String registrationNumber;
@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
private List<Address> addresses = new ArrayList<>();
//Getters and setters are omitted for brevity
public void addAddress(Address address) {
addresses.add(address);
address.getOwners().add(this);
}
public void removeAddress(Address address) {
addresses.remove(address);
address.getOwners().remove(this);
}
}
@Entity(name = "Address")
public static class Address {
@Id
@GeneratedValue
private Long id;
private String street;
@Column(name = "`number`")
private String number;
private String postalCode;
@ManyToMany(mappedBy = "addresses")
private List<Person> owners = new ArrayList<>();
}Bidirectional many-to-many with link entity
@Entity(name = "Person")
public static class Person implements Serializable {
@Id
@GeneratedValue
private Long id;
@NaturalId
private String registrationNumber;
@OneToMany(
mappedBy = "person",
cascade = CascadeType.ALL,
orphanRemoval = true
)
private List<PersonAddress> addresses = new ArrayList<>();
public void addAddress(Address address) {
PersonAddress personAddress = new PersonAddress(this, address);
addresses.add(personAddress);
address.getOwners().add(personAddress);
}
public void removeAddress(Address address) {
PersonAddress personAddress = new PersonAddress(this, address);
address.getOwners().remove(personAddress);
addresses.remove(personAddress);
personAddress.setPerson(null);
personAddress.setAddress(null);
}
}
@Entity(name = "PersonAddress")
public static class PersonAddress implements Serializable {
@Id
@ManyToOne
private Person person;
@Id
@ManyToOne
private Address address;
}
@Entity(name = "Address")
public static class Address implements Serializable {
@Id
@GeneratedValue
private Long id;
private String street;
@Column(name = "`number`")
private String number;
private String postalCode;
@OneToMany(
mappedBy = "address",
cascade = CascadeType.ALL,
orphanRemoval = true
)
private List<PersonAddress> owners = new ArrayList<>();
}