The following sections show how to set the join column for one to one map in JPA.
We use the @JoinColumn
annotation to
set the join column.
@OneToOne @JoinColumn(name="DEPT_ID") private Department department;
The following code is from Department.java.
package com.java2s.common; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.OneToOne; @Entity public class Department { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private long id; private String name; @OneToOne(mappedBy="department") private Person person; public Person getPerson() { return person; } public void setPerson(Person person) { this.person = person; } public long getId() { return id; } public void setId(long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "Department [id=" + id + ", name=" + name + ", person=" + person + "]"; } }
The following code is from Person.java.
package com.java2s.common; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.OneToOne; @Entity public class Person { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private long id; private String name; @OneToOne @JoinColumn(name="DEPT_ID") private Department department; public Person() {} public Person(String name) { this.name = name; } public Department getDepartment() { return department; } public void setDepartment(Department department) { this.department = department; } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "Person [id=" + id + ", name=" + name + "]"; } }
The following code is from PersonDaoImpl.java.
package com.java2s.common; import java.util.List; import javax.persistence.EntityManager; import javax.persistence.PersistenceContext; import javax.persistence.Query; import org.springframework.transaction.annotation.Transactional; @Transactional public class PersonDaoImpl { public void test(){ Person p1 = new Person("Tom"); p1.setName("Tom"); Department d = new Department(); d.setName("Design"); p1.setDepartment(d); d.setPerson(p1); em.persist(p1); em.persist(d); Query query = em.createQuery("SELECT e FROM Person e"); List<Person> list = (List<Person>) query.getResultList(); System.out.println(list.get(0).getDepartment()); } @PersistenceContext private EntityManager em; }
The following is the database dump.
Table Name: DEPARTMENT Row: Column Name: ID, Column Type: BIGINT: Column Value: 1 Column Name: NAME, Column Type: VARCHAR: Column Value: Design Table Name: PERSON Row: Column Name: ID, Column Type: BIGINT: Column Value: 1 Column Name: NAME, Column Type: VARCHAR: Column Value: Tom Column Name: DEPT_ID, Column Type: BIGINT: Column Value: 1