Let's move on to **practice**. In the previous chapter, we implemented the **DAO layer** as well as the **Service layer** for the `Employee` entity. In this task, **you need to do the same** for the `Department` entity.
Interfaces such as `DepartmentDao` and `DepartmentService` have already been created for you. In this task, **you should work in implementation classes**, such as `DepartmentDaoImpl` and `DepartmentServiceImpl`.
Your task is to implement all the methods specified in the interfaces.


Here's the workflow for the task:

1. Set up the database connection in `hibernate.cfg.xml`;
2. Implement the interfaces in the implementation classes;
3. Implement the necessary methods in the implementation classes;
4. You can implement them similarly to how we did it in the previous chapter. It's not difficult. You just need to change the entity names;
5. Don't forget to use `HibernateUtil`;
6. Run the **integration tests** to check your solution.

>Note
>
>To ensure that the integration tests work correctly, you need to **execute the following command** in the MySQL Workbench query. This command will grant permission to delete data from the table for the tests to run correctly. Don't worry. **This database is a test database;** later, when we test all the necessary methods and are ready to complete the project, **we will create another database** that will no longer be a test one.

Command:

<link
        rel="stylesheet"
        href="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.62.3/codemirror.min.css"
/>
<link
        rel="stylesheet"
        href="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.62.3/theme/dracula.min.css"
/>


<link
        rel="stylesheet"
        href="https://codefinity-content-media-v2.s3.eu-west-1.amazonaws.com/courses/c1087363-9025-4c37-8d5e-983a32a007e9/buttons-section/hint-solution-with-copyable-%26%3Dhighlighted-code.css"
/>

<div class="button-container">
    <button
            class="button"
            onclick="toggleBlock6('hint-block6', 'solution-block6')"
    >
        Hint
    </button>
    <button
            class="button"
            onclick="toggleBlock6('solution-block6', 'hint-block6')"
    >
        Solution
    </button>
</div>


<div id="hint-block6" class="block hint-styling-block">
    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 the command for <b>SQL Workbench</b>. <br/>
    4. You can use main to test your solution.
</div>

<div id="solution-block6" class="block solution-styling-block">
    
    <textarea id="code-6" class="language-java">
// DepartmentDaoImpl

public class DepartmentDaoImpl implements DepartmentDao {
    private final SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

    @Override
    public Department add(Department department) {
        Session session = null;
        Transaction transaction = null;
        try {
            session = sessionFactory.openSession();
            transaction = session.beginTransaction();
            session.persist(department);
            transaction.commit();
        } catch (Exception e) {
            if (transaction != null) {
                transaction.rollback();
                throw new RuntimeException("Can't add new Department", e);
            }
        } finally {
            if (session != null) {
                session.close();
            }
        }
        return department;
    }

    @Override
    public Department getById(int id) {
        Session session = null;
        Department department = null;
        try {
            session = sessionFactory.openSession();
            department = session.get(Department.class, id);
        } catch (Exception e) {
            throw new HibernateException("Can't get Department by ID " + id, e);
        } finally {
            if (session != null) {
                session.close();
            }
        }
        return department;
    }
}

//DepartmentServiceImpl

public class DepartmentServiceImpl implements DepartmentService {
    private final DepartmentDao departmentDao = new DepartmentDaoImpl();

    @Override
    public Department add(Department department) {
        return departmentDao.add(department);
    }

    @Override
    public Department getById(int id) {
        Department department = departmentDao.getById(id);
        if (department != null) {
            return departmentDao.getById(id);
        } else {
            throw new NoSuchElementException("Can't get department by ID " + id);
        }
    }

    @Override
    public String getDepartmentNameById(int id) {
        Department department = getById(id);
        String departmentName = department.getName();
        if (departmentName != null) {
            return departmentName;
        } else {
            throw new NullPointerException("The department's name is null, " +
                    "or there is no name for an department with ID " + id);
        }
    }
}</textarea>

    <button class="copy-button" onclick="handleClick6('code-6')">
        <svg
                width="20"
                height="20"
                x="0"
                y="0"
                viewBox="0 0 32 32"
                style="enable-background: new 0 0 512 512"
                xml:space="preserve"
                class=""
        >
      <g>
        <path
                d="m26.121 6.707-3.828-3.828A2.98 2.98 0 0 0 20.172 2H12a3.003 3.003 0 0 0-3 3v1H8a3.003 3.003 0 0 0-3 3v18a3.003 3.003 0 0 0 3 3h12a3.003 3.003 0 0 0 3-3v-1h1a3.003 3.003 0 0 0 3-3V8.829a2.982 2.982 0 0 0-.879-2.122ZM22 5.414 23.586 7H22ZM20 28H8a1.001 1.001 0 0 1-1-1V9a1.001 1.001 0 0 1 1-1h8v3a2.002 2.002 0 0 0 2 2h3v14a1 1 0 0 1-1 1ZM18 9.414 19.586 11H18ZM24 24h-1V12.829a2.982 2.982 0 0 0-.879-2.122l-3.828-3.828A2.98 2.98 0 0 0 16.171 6H11V5a1.001 1.001 0 0 1 1-1h8v3a2.002 2.002 0 0 0 2 2h3v14a1 1 0 0 1-1 1Zm-6-8h-8a1 1 0 0 1 0-2h8a1 1 0 0 1 0 2Zm0 4h-8a1 1 0 0 1 0-2h8a1 1 0 0 1 0 2Zm0 4h-8a1 1 0 0 1 0-2h8a1 1 0 0 1 0 2Z"
                fill="#a6b8e6"
                opacity="1"
                data-original="#000000"
                class=""
        ></path>
      </g>
    </svg>
    </button>
</div>

<script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.62.3/codemirror.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.62.3/mode/clike/clike.min.js"></script>


<script src="https://cdn.jsdelivr.net/npm/notiflix@2.7.0/dist/notiflix-aio-2.7.0.min.js"></script>

<script>
    function onPageLoad6() {
        var editor = CodeMirror.fromTextArea(document.getElementById("code-6"), {
            lineNumbers: true,
            mode: "text/x-java",
            theme: "dracula",
        });

        // ----------> HIGHLIGHT <----------
        editor.markText(
            { line: 0, ch: 0 },
            { line: 0, ch: 0 },
            { className: "specific" }
        );

        editor.markText(
            { line: 0, ch: 0 },
            { line: 0, ch: 0 },
            { className: "specific" }
        );

        editor.markText(
            { line: 0, ch: 0 },
            { line: 0, ch: 0 },
            { className: "specific" }
        );

        editor.markText(
            { line: 0, ch: 0 },
            { line: 0, ch: 0 },
            { className: "specific" }
        );

        editor.markText(
            { line: 0, ch: 0 },
            { line: 0, ch: 0 },
            { className: "specific" }
        );

        // Initially hide both the hint and solution blocks
        hideBlock6("hint-block6");
        hideBlock6("solution-block6");
    }

    // Copy Button handler
    const handleClick6 = (codeBlock) => {
        const textarea = document.getElementById(codeBlock);
        const copiedText = textarea.value;

        navigator.clipboard.writeText(copiedText);

        Notiflix.Notify.Success("Copied to clipboard!", {
            timeout: 2000,
            width: "260px",
            position: "center-top",
            textColor: "#ff5549",
        });
    };

    // Function to toggle the visibility of a block
    const toggleBlock6 = (blockId) => {
        const block = document.getElementById(blockId);

        if (block.style.display === "none" || block.style.display === "") {
            hideBlock6("hint-block6");
            hideBlock6("solution-block6");
            showBlock6(blockId);
        } else {
            hideBlock6(blockId);
        }
    };

    // Function to show a block
    const showBlock6 = (blockId) => {
        const block = document.getElementById(blockId);
        block.style.display = "block";
    };

    // Function to hide a block
    const hideBlock6 = (blockId) => {
        const block = document.getElementById(blockId);
        block.style.display = "none";
    };

    const imgElement6 = document.createElement("img");
    imgElement6.src = "nonexistent-image";
    imgElement6.style.display = "none";
    imgElement6.onerror = onPageLoad6;

    document.body.appendChild(imgElement6);
</script>

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: Implementing DAO