Java Tutorial/JPA/Named Query

EJB QL GroupBy

File: Main.java

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;
public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();
  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    Query query = em.createQuery("SELECT d.name, COUNT(e) FROM Department d JOIN d.students e GROUP BY d.name");
    System.out.println(query.getResultList());
    em.getTransaction().rumit();
    em.close();
    emf.close();
    Helper.checkData();
  }
}

EJB QL Group By And Aggregate Function

File: Main.java

import java.util.Date;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.FlushModeType;
import javax.persistence.Persistence;
import javax.persistence.Query;
public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();
  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    Query query = em.createQuery("SELECT d.name, AVG(e.salary) FROM Department d JOIN d.students e GROUP BY d.name");
    System.out.println(query.getResultList());
    em.getTransaction().rumit();
    em.close();
    emf.close();
    Helper.checkData();
  }
}

EJB QL Group Named Query With Named Queries

File: Main.java

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.NoResultException;
import javax.persistence.Persistence;
public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();
  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    int id = 1;
    try {
      Student s = (Student) em.createNamedQuery("Student.findByPrimaryKey").setParameter("id", 1)
          .getSingleResult();
    } catch (NoResultException e) {
    }
    em.getTransaction().rumit();
    em.close();
    emf.close();
    Helper.checkData();
  }
}

EJB QL MemberOf function

File: Main.java

import java.util.Date;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.FlushModeType;
import javax.persistence.Persistence;
import javax.persistence.Query;
public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();
  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    Query query = em.createQuery("SELECT e FROM Student e WHERE e MEMBER OF e.directs");
    System.out.println(query.getResultList());
    em.getTransaction().rumit();
    em.close();
    emf.close();
    Helper.checkData();
  }
}

Named Query With Int Parameter

File: Main.java

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.NoResultException;
import javax.persistence.Persistence;
public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();
  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    int id = 1;
    try {
      Student s = (Student) em.createNamedQuery("Student.findByPrimaryKey").setParameter("id", 1)
          .getSingleResult();
    } catch (NoResultException e) {
    }
    em.getTransaction().rumit();
    em.close();
    emf.close();
    Helper.checkData();
  }
}

Named Query With String Parameter

File: Main.java

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.NoResultException;
import javax.persistence.Persistence;
public class Main {
  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");
  static EntityManager em = emf.createEntityManager();
  public static void main(String[] a) throws Exception {
    em.getTransaction().begin();
    String name = "Mark";
    try {
      Student s = (Student) em.createNamedQuery("Student.findByName").setParameter("name", name)
          .getSingleResult();
    } catch (NoResultException e) {
    }
    em.getTransaction().rumit();
    em.close();
    emf.close();
    Helper.checkData();
  }
}