This example demonstrates how to use @MappedSuperclass with @OneToMany relationship.
Example
@MappedSuperclass
public class Employee {
@Id
@GeneratedValue
private long id;
private String name;
@OneToMany(cascade = CascadeType.ALL)
private List<Phone> phones;
.............
}
@Entity
public class Phone {
@Id
@GeneratedValue
private long id;
private String type;
private String number;
.............
}
@Entity
@Table(name = "FULL_TIME_EMP")
@AttributeOverrides({
@AttributeOverride(name = "name", column = @Column(name = "FULL_TIME_EMP_NAME"))
})
public class FullTimeEmployee extends Employee {
private int salary;
.............
}
@Entity
@Table(name = "PART_TIME_EMP")
public class PartTimeEmployee extends Employee {
private int hourlyRate;
.............
}
public class ExampleMain {
public static void main(String[] args) {
EntityManagerFactory emf =
Persistence.createEntityManagerFactory("example-unit");
try {
EntityManager em = emf.createEntityManager();
nativeQuery(em, "SHOW TABLES");
nativeQuery(em, "SHOW COLUMNS from FULL_TIME_EMP");
nativeQuery(em, "SHOW COLUMNS from PART_TIME_EMP");
nativeQuery(em, "SHOW COLUMNS from PHONE");
} finally {
emf.close();
}
}
public static void nativeQuery(EntityManager em, String s) {
System.out.printf("'%s'%n", s);
Query query = em.createNativeQuery(s);
List list = query.getResultList();
for (Object o : list) {
if (o instanceof Object[]) {
System.out.println(Arrays.toString((Object[]) o));
} else {
System.out.println(o);
}
}
}
} 'SHOW TABLES' [FULL_TIME_EMP, PUBLIC] [FULL_TIME_EMP_PHONE, PUBLIC] [PART_TIME_EMP, PUBLIC] [PART_TIME_EMP_PHONE, PUBLIC] [PHONE, PUBLIC] 'SHOW COLUMNS from FULL_TIME_EMP' [ID, BIGINT(19), NO, PRI, NULL] [FULL_TIME_EMP_NAME, VARCHAR(255), YES, , NULL] [SALARY, INTEGER(10), NO, , NULL] 'SHOW COLUMNS from PART_TIME_EMP' [ID, BIGINT(19), NO, PRI, NULL] [NAME, VARCHAR(255), YES, , NULL] [HOURLYRATE, INTEGER(10), NO, , NULL] 'SHOW COLUMNS from PHONE' [ID, BIGINT(19), NO, PRI, NULL] [NUMBER, VARCHAR(255), YES, , NULL] [TYPE, VARCHAR(255), YES, , NULL]
Persisting and loading data
public class ExampleMain2 {
public static void main(String[] args) throws Exception {
EntityManagerFactory emf =
Persistence.createEntityManagerFactory("example-unit");
try {
persistEntities(emf);
runNativeQueries(emf);
loadEntities(emf);
} finally {
emf.close();
}
}
private static void persistEntities(EntityManagerFactory emf) throws Exception {
System.out.println("-- Persisting entities --");
EntityManager em = emf.createEntityManager();
FullTimeEmployee e1 = new FullTimeEmployee();
e1.setName("Sara");
e1.setSalary(100000);
Phone p1 = new Phone();
p1.setType("cell");
p1.setNumber("111-222-3232");
Phone p2 = new Phone();
p2.setType("home");
p2.setNumber("212-222-3232");
e1.setPhones(Arrays.asList(p1, p2));
System.out.println(e1);
PartTimeEmployee e2 = new PartTimeEmployee();
e2.setName("Robert");
e2.setHourlyRate(60);
Phone p3 = new Phone();
p3.setType("cell");
p3.setNumber("123-323-9999");
e2.setPhones(Arrays.asList(p3));
System.out.println(e2);
em.getTransaction().begin();
em.persist(e1);
em.persist(e2);
em.getTransaction().commit();
em.close();
}
private static void runNativeQueries(EntityManagerFactory emf) {
System.out.println("-- Native queries --");
EntityManager em = emf.createEntityManager();
ExampleMain.nativeQuery(em, "Select * from FULL_TIME_EMP");
ExampleMain.nativeQuery(em, "Select * from PART_TIME_EMP");
ExampleMain.nativeQuery(em, "Select * from PHONE");
}
private static void loadEntities(EntityManagerFactory emf) {
System.out.println("-- Loading entities --");
EntityManager em = emf.createEntityManager();
List<Employee> entityAList = em.createQuery("Select t from FullTimeEmployee t")
.getResultList();
entityAList.forEach(System.out::println);
entityAList = em.createQuery("Select t from PartTimeEmployee t")
.getResultList();
entityAList.forEach(System.out::println);
em.close();
}
} -- Persisting entities -- FullTimeEmployee{Employee{id=0, name='Sara', phones=[Phone{id=0, type='cell', number='111-222-3232'}, Phone{id=0, type='home', number='212-222-3232'}]}, salary=100000} PartTimeEmployee{Employee{id=0, name='Robert', phones=[Phone{id=0, type='cell', number='123-323-9999'}]}, hourlyRate='60'} -- Native queries -- 'Select * from FULL_TIME_EMP' [1, Sara, 100000] 'Select * from PART_TIME_EMP' [4, Robert, 60] 'Select * from PHONE' [2, 111-222-3232, cell] [3, 212-222-3232, home] [5, 123-323-9999, cell] -- Loading entities -- FullTimeEmployee{Employee{id=1, name='Sara', phones=[Phone{id=2, type='cell', number='111-222-3232'}, Phone{id=3, type='home', number='212-222-3232'}]}, salary=100000} PartTimeEmployee{Employee{id=4, name='Robert', phones=[Phone{id=5, type='cell', number='123-323-9999'}]}, hourlyRate='60'}
Example ProjectDependencies and Technologies Used: - h2 1.4.196: H2 Database Engine.
- hibernate-core 5.2.10.Final: The core O/RM functionality as provided by Hibernate.
Implements javax.persistence:javax.persistence-api version 2.1 - JDK 1.8
- Maven 3.3.9
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