How to define composite foreign key mapping in hibernate? - mysql

Question

I have two tables: users and userdetails as follows:
package com.example.easynotes.model;
import javax.persistence.*;
import java.io.Serializable;
#Entity
#Table(name = "users")
#IdClass(UserID.class)
public class User implements Serializable {
#Id
int id;
#Id
String name;
String department;
//getters and setters
}
The userdetails classes will be this:
public class UserDetails implements Serializable{
int id;
String name;
String address;
String otherFields;
//getters and setters
}
id and name in users is a composite primary and I want the same fields in userdetails to be the foreign key. How can I achieve this in hibernate ?

Answer 1

We need to put both key in #Embeddable to detach compound key thenafter, put it in User Entity using #EmbeddedId and map both primary key using Hibernate Relational Mapping...
There are two option to Composite Primary Key:
Using #EmbeddedId
Using #IdClass()
Here down is example:
----------------------------------- Using EmbeddedId -----------------------------------
Compound primary key:
#Embeddable
public class UserIdName implements Serializable {
int id;
String name;
// getter and setter
}
User:
#Entity
#Table(name = "users")
public class USER{
#EmbeddedId
private UserIdName id;
String department;
#OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
private Set<Userdetail> userdetail;
// getter and setter
}
UserDetails:
#Entity
#Table(name = "Userdetail")
public class Userdetail {
#Id
private int detail_id;
#ManyToOne
#JoinColumns({ #JoinColumn(name = "id", referencedColumnName = "id"),
#JoinColumn(name = "name", referencedColumnName = "name") })
private USER user;
String address;
String otherFields;
// getter setter
}
----------------------------------- Using IdClass -----------------------------------
Compound primary key:
public class UserIdName implements Serializable {
int id;
String name;
// getter and setter
}
User:
#Entity
#Table(name = "users")
#IdClass(UserIdName.class)
public class USER{
#Id
int id;
#Id
String name;
String department;
#OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
private Set<Userdetail> userdetail;
// getter and setter
}
UserDetails:
#Entity
#Table(name = "Userdetail")
public class Userdetail {
#Id
private int detail_id;
#ManyToOne
#JoinColumns({ #JoinColumn(name = "id", referencedColumnName = "id"),
#JoinColumn(name = "name", referencedColumnName = "name") })
private USER user;
String address;
String otherFields;
// getter setter
}
-> If you wanna insert both foreign key manually try below code
Put this code in UserDetails
#ManyToOne
#JoinColumn(name = "id", referencedColumnName = "id", insertable = false, updatable = false)
#JoinColumn(name = "name", referencedColumnName = "name", insertable = false, updatable = false)
private USER user;
#Column(name="id")
private int id;
#Column(name="name")
private String name
// don't forget to put getter setter
User Table:
User Detail Table: