# It's time to practice

In the previous chapter, we implemented 2 methods in the `Employee` service layer. We used **queries** to fetch the necessary data, and now you will have to do a similar task.

Your work will involve 4 classes:
1. `DepartmentDaoImpl`;
2. `EmployeeDaoImpl`;
3. `DepartmentServiceImpl`;
4. `EmployeeServiceImpl`.

You need to implement methods such as `getAll` and `getEmployeesWithSalaryMoreThan(Double salary)`. To implement these methods, you will need to use either `Query` or `NativeQuery`, depending on what you choose to use, **HQL** or **SQL**. You will also need to use parameter substitution and return a list.

After you implement the methods, you can **test your solution** in the `Main` class, and then **run the tests** that I have written for you to check if you have implemented everything correctly.

>Note
>
>Don't forget to set up a connection to your database in `hibernate.cfg.xml`.

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    1. Use the code from the previous chapter as a hint. <br/>
    2. Don't forget to change the data in <code>hibernate.cfg.xml</code>. <br/>
    3. Don't forget about setting parameters in the query. This is done using the <code>setParameter()</code> method. <br/>
    4. To obtain a list from the query, use the <code>getResultList()</code> method. <br/>
    5. You can use main to test your solution.
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// DepartmentDaoImpl

public List<Department> getAll() {
    Session session = null;
    List<Department> departments = null;

    try {
        session = sessionFactory.openSession();

        String hql = "FROM Department";

        Query<Department> query = session.createQuery(hql, Department.class);

        departments = query.getResultList();

    } catch (Exception e) {
        System.out.println("Can't get departments" + e);
    } finally {
        if (session != null) {
            session.close();
        }
    }
    return departments;
}

//DepartmentServiceImpl

@Override
public List<Department> getAll() {
    return departmentDao.getAll();
}

//EmployeeDaoImpl

public List<Employee> getAll() {
    Session session = null;
    List<Employee> employees = null;
    try {
        session = sessionFactory.openSession();

        String hql = "FROM Employee";

        Query<Employee> query = session.createQuery(hql, Employee.class);
        employees = query.getResultList();
    } catch (Exception e) {
        System.out.println("Can't get Employees from the DB" + e);
    } finally {
        if (session != null) {
            session.close();
        }
    }
    return employees;
}

public List<Employee> getEmployeesWithSalaryMoreThan(Double salary) {
    Session session = null;
    List<Employee> employees = null;
    try {
        session = sessionFactory.openSession();

        String hql = "FROM Employee WHERE salary > :salary";

        Query<Employee> query = session.createQuery(hql, Employee.class);
        query.setParameter("salary", salary);
        employees = query.getResultList();
    } catch (Exception e) {
        System.out.println("Can't get Employees from the DB" + e);
    } finally {
        if (session != null) {
            session.close();
        }
    }
    return employees;
}

//EmployeeServiceImpl

@Override
public List<Employee> getAll() {
    return employeeDao.getAll();
}

@Override
public List<Employee> getEmployeesWithSalaryMoreThan(Double salary) {
    return employeeDao.getEmployeesWithSalaryMoreThan(salary);
}
</textarea>

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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: Query

It's time to practice