In Criteria API following method of CriteriaBuilder can be used to execute a database function.
Expression<T> function(String name, Class<T> type, Expression<?>... args);
Quick Example
Following example uses H2 database DATEDIFF function.
DATEDIFF(datetimeField, aDateAndTime, bDateAndTime)
Above function returns the number of date-time unit between two date-time values in long. The 'datetimeField' indicates the unit.
...
CriteriaQuery<Object[]> query = criteriaBuilder.createQuery(Object[].class);
Root<Employee> employee = query.from(Employee.class);
query.multiselect(employee.get(Employee_.name),
criteriaBuilder.function("DATEDIFF", Long.class,
criteriaBuilder.literal("YEAR"),
employee.get(Employee_.JOIN_DATE),
criteriaBuilder.literal(Timestamp.valueOf(LocalDateTime.now()))
));
List<Object[]> resultList = entityManager.createQuery(query).getResultList();
.......
Complete Example
JPA Entity
@Entity
public class Employee {
@Id
@GeneratedValue
private long id;
private String name;
private Timestamp joinDate;
private long salary;
.............
}
Calling database function
public class ExampleMain {
private static EntityManagerFactory entityManagerFactory =
Persistence.createEntityManagerFactory("example-unit");
public static void main(String[] args) {
try {
persistEmployees();
findEmployeeWithEmploymentYears();
} finally {
entityManagerFactory.close();
}
}
private static void findEmployeeWithEmploymentYears() {
System.out.println("-- Employee name with employment years --");
EntityManager entityManager = entityManagerFactory.createEntityManager();
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Object[]> query = criteriaBuilder.createQuery(Object[].class);
Root<Employee> employee = query.from(Employee.class);
query.multiselect(employee.get(Employee_.name),
criteriaBuilder.function("DATEDIFF", Long.class,
criteriaBuilder.literal("YEAR"),
employee.get(Employee_.JOIN_DATE),
criteriaBuilder.literal(Timestamp.valueOf(LocalDateTime.now()))
));
List<Object[]> resultList = entityManager.createQuery(query).getResultList();
resultList.forEach(arr -> System.out.println(Arrays.toString(arr)));
entityManager.close();
}
public static void persistEmployees() {
Employee employee1 = Employee.create("Diana", 3000, LocalDate.of(1999, 11, 15));
Employee employee2 = Employee.create("Rose", 4000, LocalDate.of(2011, 5, 1));
Employee employee3 = Employee.create("Denise", 1500, LocalDate.of(2006, 1, 10));
Employee employee4 = Employee.create("Mike", 2000, LocalDate.of(2015, 8, 20));
EntityManager em = entityManagerFactory.createEntityManager();
em.getTransaction().begin();
em.persist(employee1);
em.persist(employee2);
em.persist(employee3);
em.persist(employee4);
em.getTransaction().commit();
em.close();
System.out.println("-- employee persisted --");
System.out.println(employee1);
System.out.println(employee2);
System.out.println(employee3);
System.out.println(employee4);
}
} -- employee persisted -- Employee{id=1, name='Diana', joinDate=1999-11-14 18:00:00.0, salary=3000} Employee{id=2, name='Rose', joinDate=2011-04-30 19:00:00.0, salary=4000} Employee{id=3, name='Denise', joinDate=2006-01-09 18:00:00.0, salary=1500} Employee{id=4, name='Mike', joinDate=2015-08-19 19:00:00.0, salary=2000} -- Employee name with employment years -- [Diana, 20] [Rose, 8] [Denise, 13] [Mike, 4]
Example ProjectDependencies and Technologies Used: - h2 1.4.199: H2 Database Engine.
- hibernate-core 5.4.2.Final: Hibernate's core ORM functionality.
Implements javax.persistence:javax.persistence-api version 2.2 - hibernate-jpamodelgen 5.4.2.Final: Annotation Processor to generate JPA 2 static metamodel classes.
- JDK 1.8
- Maven 3.5.4
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