JPQL DELETE queries can be used to delete entity objects in database. Following is the general syntax:
DELETE FROM entity_name [[AS] identification_variable] [where_clause]
DELETE queries can only be executed in a transaction and the changes are only visible to other users after commit.
Example
Entity
@Entity
public class Employee {
@Id
@GeneratedValue
private long id;
private String name;
private double salary;
private String dept;
.............
}
Executing DELETE query
public class ExampleMain {
private static EntityManagerFactory entityManagerFactory =
Persistence.createEntityManagerFactory("example-unit");
public static void main(String[] args) {
try {
persistEmployees();
findAllEmployees();
deleteEmployeeByName();
findAllEmployees();
deleteAllEmployees();
findAllEmployees();
} finally {
entityManagerFactory.close();
}
}
public static void persistEmployees() {
Employee employee1 = Employee.create("Diana", 2000, "IT");
Employee employee2 = Employee.create("Rose", 3500, "Admin");
Employee employee3 = Employee.create("Denise", 2500, "Admin");
Employee employee4 = Employee.create("Mike", 4000, "IT");
Employee employee5 = Employee.create("Linda", 4500, "Sales");
EntityManager em = entityManagerFactory.createEntityManager();
em.getTransaction().begin();
em.persist(employee1);
em.persist(employee2);
em.persist(employee3);
em.persist(employee4);
em.persist(employee5);
em.getTransaction().commit();
em.close();
}
private static void findAllEmployees() {
EntityManager em = entityManagerFactory.createEntityManager();
System.out.println("-- All employees --");
Query query = em.createQuery(
"SELECT e FROM Employee e");
List<Employee> resultList = query.getResultList();
System.out.println("Employees count: "+resultList.size());
resultList.forEach(System.out::println);
em.close();
}
private static void deleteEmployeeByName() {
System.out.println("-- delete employee by name 'Mike' --");
EntityManager em = entityManagerFactory.createEntityManager();
em.getTransaction().begin();
Query query = em.createQuery("DELETE FROM Employee e WHERE e.name = :employeeName ");
query.setParameter("employeeName", "Mike");
int rowsDeleted = query.executeUpdate();
System.out.println("entities deleted: " + rowsDeleted);
em.getTransaction().commit();
em.close();
}
private static void deleteAllEmployees() {
System.out.println("-- delete all employees --");
EntityManager em = entityManagerFactory.createEntityManager();
em.getTransaction().begin();
Query query = em.createQuery("DELETE FROM Employee e ");
int rowsDeleted = query.executeUpdate();
System.out.println("entities deleted: " + rowsDeleted);
em.getTransaction().commit();
em.close();
}
} -- All employees -- Employees count: 5 Employee{id=1, name='Diana', salary=2000.0, dept='IT'} Employee{id=2, name='Rose', salary=3500.0, dept='Admin'} Employee{id=3, name='Denise', salary=2500.0, dept='Admin'} Employee{id=4, name='Mike', salary=4000.0, dept='IT'} Employee{id=5, name='Linda', salary=4500.0, dept='Sales'} -- delete employee by name 'Mike' -- entities deleted: 1 -- All employees -- Employees count: 4 Employee{id=1, name='Diana', salary=2000.0, dept='IT'} Employee{id=2, name='Rose', salary=3500.0, dept='Admin'} Employee{id=3, name='Denise', salary=2500.0, dept='Admin'} Employee{id=5, name='Linda', salary=4500.0, dept='Sales'} -- delete all employees -- entities deleted: 4 -- All employees -- Employees count: 0
Example ProjectDependencies and Technologies Used: - h2 1.4.197: H2 Database Engine.
- hibernate-core 5.3.1.Final: Hibernate's core ORM functionality.
Implements javax.persistence:javax.persistence-api version 2.2 - JDK 1.8
- Maven 3.5.4
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