# 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: 

```
[Employee(id=1, name=John, salary=55000.0, hireDate=2021-10-05, department=Department(id=1, name=Marketing, location=Head Office), role=Role(id=1, name=Marketing Specialist, description=A dynamic role focused on developing and implementing strategies to promote brand awareness and drive product sales. Responsibilities include market research, content creation, and campaign management to enhance engagement and achieve business goals.)), Employee(id=2, name=Bob, salary=70000.0, hireDate=2022-02-18, department=Department(id=2, name=Development, location=IT Office), role=Role(id=2, name=Software Engineer, description=A software engineer writes and maintains the code for computer applications and systems.))]
```

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<div id="hint-block6" class="block hint-styling-block">
    1. First, you need to implement the methods from the <code>RoleDao</code> interface. You've done this many times before, so there shouldn't be any problems. <br/>
    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 <code>session.merge()</code> method.<br/>
    3. To implement the <code>setRoleById()</code> method and override it, you can use the template from the previous chapter. You need to do the same thing. <br/>
    4. Run the main class and compare your result with the expected one.
</div>

<div id="solution-block6" class="block solution-styling-block">
    
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// 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!");
    }
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Every backend developer must be proficient in working with various databases. Connecting a database to the code and performing data operations directly from Java code to execute SQL queries and various data operations directly from the code. JDBC and Hibernate help developers with this. It's time to learn how to connect a database to your IDE, use tables from this database, and manipulate data!

Why do we need a database? How does the interaction between a database and code work? What tools are used for different types of databases? You will learn all about this in this section!

This section will tell you how to set up and use Hibernate. You will learn how this framework works, what ORM is, and how to work with databases efficiently. You will also learn to write basic operations with a connected database, demonstrating your skills in practice!

In this section, we will complete work on the project's foundation for employee management in the company. We will add the remaining operations and one more entity.

Java Data Manipulation with Hibernate

Challenge: Role Layers Implementation

Task