Following example shows how to retrieve query results of type Tuple . Tuple contains ordered query results which can be accessed in different ways. Following is Tuple snippet:
package javax.persistence;
...
public interface Tuple {
<X> X get(TupleElement<X> tupleElement);
<X> X get(String alias, Class<X> type);
Object get(String alias);
<X> X get(int i, Class<X> type);
Object get(int i);
Object[] toArray();
List<TupleElement<?>> getElements();
}
We can use following method of EntityManager to create Tuple query:
public <T> TypedQuery<T> createQuery(String query, Class<T> resultClass);
For example:
TypedQuery<Tuple> query = entityManager.createQuery("SELECT e.name, e.salary FROM Employee e", Tuple.class);
List<Tuple> resultList = query.getResultList();
Example
Entity
@Entity
public class Employee {
@Id
@GeneratedValue
private long id;
private String name;
private long salary;
private String dept;
.............
}
Using Tuple
public class ExampleMain {
private static EntityManagerFactory entityManagerFactory =
Persistence.createEntityManagerFactory("example-unit");
public static void main(String[] args) {
try {
persistEmployees();
findEmployeeSalaries();
} finally {
entityManagerFactory.close();
}
}
public static void persistEmployees() {
Employee employee1 = Employee.create("Diana", 3000, "IT");
Employee employee2 = Employee.create("Rose", 4000, "Admin");
Employee employee3 = Employee.create("Denise", 1500, "Sales");
Employee employee4 = Employee.create("Mike", 2000, "IT");
EntityManager em = entityManagerFactory.createEntityManager();
em.getTransaction().begin();
em.persist(employee1);
em.persist(employee2);
em.persist(employee3);
em.persist(employee4);
em.getTransaction().commit();
em.close();
}
private static void findEmployeeSalaries() {
System.out.println("-- Employee names and salaries --");
EntityManager em = entityManagerFactory.createEntityManager();
TypedQuery<Tuple> query = em.createQuery("SELECT e.name, e.salary FROM Employee e", Tuple.class);
List<Tuple> resultList = query.getResultList();
resultList.forEach(tuple -> System.out.printf("name: %s, salary: %s%n", tuple.get(0),
tuple.get(1, Long.class)));
}
} -- Employee names and salaries -- name: Diana, salary: 3000 name: Rose, salary: 4000 name: Denise, salary: 1500 name: Mike, salary: 2000
Example ProjectDependencies and Technologies Used: - h2 1.4.197: H2 Database Engine.
- hibernate-core 5.2.13.Final: The core O/RM functionality as provided by Hibernate.
Implements javax.persistence:javax.persistence-api version 2.1 - JDK 1.8
- Maven 3.5.4
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