Java Tutorial/JPA/Lazy Eager

Detachment Triggered Lazy Loading

File: Main.java

import java.util.List;
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();
    Student emp1 = new Student();
    emp1.setId(1);
    em.persist(emp1);
    Query query = em.createQuery("SELECT e FROM Student e");
    List<Student> list = (List<Student>) query.getResultList();
    System.out.println(list);
    List<Student> emps = em.createQuery("SELECT e FROM Student e").getResultList();
    for (Student emp : emps) {
      if (emp.getDepartment() != null) {
        emp.getDepartment().getName();
      }
    }
    em.getTransaction().rumit();
    em.close();
    emf.close();
    Helper.checkData();
  }
}

Detachment With Eager Loading

File: Main.java

import java.util.List;
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();
    Student emp1 = new Student();
    emp1.setId(1);
    em.persist(emp1);
    Query query = em.createQuery("SELECT e FROM Student e");
    List<Student> list = (List<Student>) query.getResultList();
    System.out.println(list);
    List<Student> emps = em.createQuery("SELECT e FROM Student e").getResultList();
    for (Student emp : emps) {
      if (emp.getDepartment() != null) {
        emp.getDepartment().getName();
      }
    }
    em.getTransaction().rumit();
    em.close();
    emf.close();
    Helper.checkData();
  }
}