Java Data Manipulation with Hibernate

Challenge: Role Layers Implementation

Task

Now let's get to the task:

Your task is to implement the methods in the classes RoleDaoImpl, RoleServiceImpl, EmployeeDaoImpl, and EmployeeServiceImpl. This is not difficult; you have done this many times. The only potential challenge might be with the updateRole method, but I'm confident you can handle it.

To test your solution, you need to run the code I have written for you in the main class. Then, you will need to compare the result with the correct result, which I will provide below.

Testing such large applications with database interaction implementation becomes increasingly challenging, so now your project will be tested by yourself (or you can peek at the Solution).

Correct output:

Link to the Task: GitHub

1. First, you need to implement the methods from the RoleDao interface. You've done this many times before, so there shouldn't be any problems.
2. For the method with role update, use the following algorithm: Retrieve the role from the database, reassign the role's fields with new values, and use the session.merge() method.
3. To implement the setRoleById() method and override it, you can use the template from the previous chapter. You need to do the same thing.
4. Run the main class and compare your result with the expected one.

// RoleDaoImpl
public class RoleDaoImpl implements RoleDao {
    SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

@Override
    public Role add(Role role) {
        Session session = null;
        Transaction transaction = null;

try {
            session = sessionFactory.openSession();
            transaction = session.beginTransaction();

session.persist(role);
            transaction.commit();
        } catch (Exception e) {
            if (transaction != null) {
                transaction.rollback();
                throw new RuntimeException("Can't add new Role", e);
            }
        } finally {
            if (session != null) {
                session.close();
            }
        }
        return role;
    }

@Override
    public Role getById(int id) {
        Session session = null;
        Role role = null;

try {
            session = sessionFactory.openSession();
            role = session.get(Role.class, id);
        } catch (Exception e) {
            throw new NoSuchElementException("Can't get Role by ID " + id, e);
        } finally {
            if (session != null) {
                session.close();
            }
        }
        return role;
    }

@Override
    public List<Role> getAll() {
        Session session = null;
        List<Role> roles = null;

try {
            session = sessionFactory.openSession();

String hql = "FROM Role";
            Query<Role> query = session.createQuery(hql, Role.class);

roles = query.getResultList();
        } catch (Exception e) {
            throw new NoSuchElementException("Can't get Employees from the DB", e);
        } finally {
            if (session != null) {
                session.close();
            }
        }
        return roles;
    }

@Override
    public Role updateRole(int id, Role newRole) {
        Session session = null;
        Role role = null;
        Transaction transaction = null;

if (newRole == null) {
            throw new NullPointerException("The `newRole` is null!");
        }

try {
            session = sessionFactory.openSession();
            transaction = session.beginTransaction();

role = getById(id);
            role.setName(newRole.getName());
            role.setDescription(newRole.getDescription());

session.merge(role);
            transaction.commit();
        } catch (Exception e) {
            if (transaction != null) {
                transaction.rollback();
            }
            throw new HibernateException("Can't update the role");
        }
        return role;
    }
}

//EmployeeDaoImpl
@Override
public Employee setRoleById(int employeeId, int roleId) {
    Employee employee = null;
    Role role = null;
    Session session = null;
    Transaction transaction = null;

try {
        session = sessionFactory.openSession();
        transaction = session.beginTransaction();

employee = getById(employeeId);
        role = roleService.getById(roleId);

employee.setRole(role);
        session.merge(employee);
        transaction.commit();
    } catch (Exception e) {
        if (transaction != null) {
            transaction.rollback();
        }
    } finally {
        if (session != null) {
            session.close();
        }
    }
    return employee;
}

//RoleServiceImpl
public class RoleServiceImpl implements RoleService {
    private final RoleDao roleDao = new RoleDaoImpl();

@Override
    public Role add(Role role) {
        return roleDao.add(role);
    }

@Override
    public Role getById(int id) {
        return roleDao.getById(id);
    }

@Override
    public List<Role> getAll() {
        return roleDao.getAll();
    }

@Override
    public Role updateRole(int id, Role newRole) {
        return roleDao.updateRole(id, newRole);
    }
}

//EmployeeServiceImpl
@Override
public Employee setRoleById(int employeeId, int roleId) {
    return employeeDao.setRoleById(employeeId, roleId);
}

@Override
public Employee setRoleById(int employeeId, Role role) {
    if (role == null) {
        throw new NullPointerException("The role is null!");
    }

List<Role> roles = roleService.getAll();

if (roles.contains(role)) {
        int roleId = role.getId();
        return setRoleById(employeeId, roleId);
    } else {
        throw new NoSuchElementException("No such role found in the database!");
    }
}

Все було зрозуміло?

Секція 2. Розділ 11