How to get Database data using Hibernate? Explained by Impl class

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package com.mysite.firstJavaDbApp.serviceImpl;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import com.mysite.firstJavaDbApp.beans.Employee;
import com.mysite.firstJavaDbApp.config.HibernateDbConfig;
import com.mysite.firstJavaDbApp.service.HibernateEmployeeService;
public class HibernateEmployeeServiceImpl implements HibernateEmployeeService {
private SessionFactory sessionFactory;
public HibernateEmployeeServiceImpl() {
 sessionFactory = HibernateDbConfig.getInstance().getSessionFactory();
}
@Override
public Boolean saveEmployee(Employee employee) {
 Session session = sessionFactory.openSession();
 Transaction tx = session.beginTransaction();
 try {
  session.persist(employee);
  tx.commit();
  return true;
 } catch (Exception e) {
  e.printStackTrace();
 }
 return false;
}
@Override
public Employee getEmployeeById(Long employeeId) {
 Session session = sessionFactory.openSession();
 Transaction tx = session.beginTransaction();
 Employee emp = null;
 try {
  emp = session.find(Employee.class, employeeId);
 } catch (Exception e) {
  e.printStackTrace();
 }
 return emp;
}
@Override
public List<Employee> getAllEmployees() {
 String query = "select * from employee";
 Session session = sessionFactory.openSession();
 Transaction tx = session.beginTransaction();
 List<Employee> employees = session.createNativeQuery(query, Employee.class).getResultList();
 return employees;
}
}