Introduction au mapping objet-relationnel (correction)

private void createEmployees(EntityManager em) {
		System.out.println("\n-- Start simple employees creation --");

		Emp king, jones, smith;

		System.out.println("==== Create employees in memory ====");

		try {
			king = new Emp("KING", "PRESIDENT", null, null,
					new SimpleDateFormat("dd-mm-yy").parse("17-11-81"), 5000, 0);
			jones = new Emp("JONES", "MANAGER", null, null,
					new SimpleDateFormat("dd-mm-yy").parse("04-12-81"), 2975, 0);
			smith = new Emp("SMITH", "CLERK", null, null,
					new SimpleDateFormat("dd-mm-yy").parse("17-12-80"), 800, 0);

		} catch (ParseException e) {
			System.err.println("ERROR CREATING EMPLOYEES (DATE PARSING PB)");
			return;
		}

		System.out.println("===== Persist employees data ====\n ");
		em.getTransaction().begin();
		try {
			em.persist(king);
			em.persist(jones);
			em.persist(smith);
			em.getTransaction().commit();
		} catch (Exception e) {
			em.getTransaction().rollback();
			e.printStackTrace();
		} finally { // Either if new employees are created or not, display the employees existing in
					// the database
			System.out.println("===== Display employees data =====");
			Query q = em.createNativeQuery("select e from employees e");
			List<Emp> empList = (List<Emp>) q.getResultList();
			System.out.println(empList);
		}
	}

private void createDepartmentWithEmployees(EntityManager em) {
		System.out.println("\n-- Start departments with employees creation --");

		System.out.println("==== Create departments in memory ====");
		Dept research = new Dept("RESEARCH", "Brest");
		Dept accounting = new Dept("ACCOUNTING", "Rennes");

		System.out.println("==== Create employees in memory ====");
		Emp king, jones, blake, scott, ford;
		try {
			king = new Emp("KING", "PRESIDENT", null, null,
					new SimpleDateFormat("dd-mm-yy").parse("17-11-81"), 5000, 0);
			jones = new Emp("JONES", "MANAGER", null, null,
					new SimpleDateFormat("dd-mm-yy").parse("04-12-81"), 2975, 0);
			blake = new Emp("BLAKE", "ANALYST", null, null,
					new SimpleDateFormat("dd-mm-yy").parse("01-05-81"), 2850, 0);
			scott = new Emp("SCOTT", "ANALYST", null, null,
					new SimpleDateFormat("dd-mm-yy").parse("09-12-82"), 3000, 0);
			ford = new Emp("FORD", "ANALYST", null, null,
					new SimpleDateFormat("dd-mm-yy").parse("03-12-81"), 3000, 0);
		} catch (ParseException e) {
			System.err.println("ERROR CREATING EMPLOYEES (DATE PARSING PB)");
			return;
		}

		System.out.println("===== Affect employees to department ====\n ");
		king.setDept(research);
		jones.setDept(research);
		blake.setDept(accounting);
		scott.setDept(accounting);
		ford.setDept(accounting);

		System.out.println("===== Add employees to department ====\n ");
		research.affectEmp(king);
		research.affectEmp(jones);
		accounting.affectEmp(blake);
		accounting.affectEmp(scott);
		accounting.affectEmp(ford);

		System.out.println("===== Affect a manager to employees ====\n ");
		jones.setManager(king);
		blake.setManager(king);
		scott.setManager(jones);
		ford.setManager(jones);

		System.out.println("===== Affect collaborators to an employee ====\n ");
		king.addLower(jones);
		king.addLower(blake);
		jones.addLower(scott);
		jones.addLower(ford);

		System.out.println("===== Persist departments and employees data ====\n ");
		em.getTransaction().begin();
		try {
			em.persist(research);
			em.persist(accounting);
			em.persist(king);
			em.persist(jones);
			em.persist(blake);
			em.persist(scott);
			em.persist(ford);
			em.getTransaction().commit();
		} catch (Exception e) {
			em.getTransaction().rollback();
			e.printStackTrace();
		} finally { // Either if new department is created or not, display the department
			System.out.println("===== Display departments data =====");
			System.out.println(em.createNativeQuery("select d from departments d").getResultList());
			System.out.println("===== Display employees data =====");
			System.out.println(em.createNativeQuery("select e from employees e").getResultList());
		}
	}

private Emp findEmployee(EntityManager em, int empno) {
		System.out.println("\n-- Start employee search --");

		Emp emp = null;
		em.getTransaction().begin();
		try {
			emp = em.find(Emp.class, empno);
			em.getTransaction().commit();
			return emp;
		} catch (Exception e) {
			em.getTransaction().rollback();
			e.printStackTrace();
		}
		return emp;
	}

private Set<Emp> findCollaborators(EntityManager em, Emp emp) {
		System.out.println("\n-- Start find employees whose manager is " +
				emp.getName() + " --");
		Set<Emp> collaborators = emp.getLowers();

		return collaborators;
	}

private void affectCommission(EntityManager em, Set<Emp> collaborators, float totalCommission) {

		// Affect a commission to the collaborators of the manager
		System.out.println("\n-- Start affect commission --");
		System.out.println("\n Affect commission to " + collaborators.size() + " employees");

		// Principles:
		// - Compute sum salaries
		// - For each employee:
		// * Compute individual commission
		// * Update database table with the new commission
		// - Display database for verification

		int totalSalary = 0;
		float commission = 0;
		for (Emp emp : collaborators)
			totalSalary += emp.getSalary();

		System.out.println("\n\t- Salaries sum: " + totalSalary);

		for (Emp emp : collaborators) {
			commission = emp.getSalary() * totalCommission / totalSalary;
			emp.setCommission(commission);
			System.out.println("\t- Commission of " + commission + " euros for " + emp);
		}

		System.out.println("===== Update employees in database =====");
		em.getTransaction().begin();
		try {
			for (Emp emp : collaborators)
				em.merge(emp);
			em.getTransaction().commit();
		} catch (Exception e) {
			em.getTransaction().rollback();
			e.printStackTrace();
		}
	}