СТЕПАН ПРИКОЛ 1

To serialize and deserialize XML using DOM parser in the `ClientMessage` class, you can add the following methods:

```java
import javax.xml.parsers.*;
import org.w3c.dom.*;
import java.io.*;

public abstract sealed class ClientMessage implements Serializable permits ClientMessage.ListMembers, ClientMessage.LoginRequest, ClientMessage.Logout, ClientMessage.Message {
    // ... existing code ...

    public static String serialize(ClientMessage message) throws ParserConfigurationException {
        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
        Document document = documentBuilder.newDocument();

        Element rootElement = document.createElement("command");
        rootElement.setAttribute("name", message.getName());

        if (message instanceof ClientMessage.LoginRequest loginRequest) {
            serializeLoginRequest(document, rootElement, loginRequest);
        } else if (message instanceof ClientMessage.ListMembers listMembers) {
            serializeListMembers(document, rootElement, listMembers);
        } else if (message instanceof ClientMessage.Message message) {
            serializeMessage(document, rootElement, message);
        } else if (message instanceof ClientMessage.Logout logout) {
            serializeLogout(document, rootElement, logout);
        }

        document.appendChild(rootElement);

        StringWriter writer = new StringWriter();
        try {
            TransformerFactory transformerFactory = TransformerFactory.newInstance();
            Transformer transformer = transformerFactory.newTransformer();
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.transform(new DOMSource(document), new StreamResult(writer));
        } catch (Exception e) {
            throw new RuntimeException(e);
        }

        return writer.toString();
    }

    private static void serializeLoginRequest(Document document, Element rootElement,
                                              ClientMessage.LoginRequest loginRequest) {
        Element nameElement = document.createElement("name");
        nameElement.setTextContent(loginRequest.getUserName());
        rootElement.appendChild(nameElement);
    }

    private static void serializeListMembers(Document document, Element rootElement,
                                             ClientMessage.ListMembers listMembers) {
        Element sessionElement = document.createElement("session");
        sessionElement.setTextContent(String.valueOf(listMembers.getSessionID()));
        rootElement.appendChild(sessionElement);
    }

    private static void serializeMessage(Document document, Element rootElement,
                                         ClientMessage.Message message) {
        Element messageElement = document.createElement("message");
        messageElement.setTextContent(message.getMessageText());
        Element sessionElement = document.createElement("session");
        sessionElement.setTextContent(String.valueOf(message.getSessionID()));
        rootElement.appendChild(messageElement);
        rootElement.appendChild(sessionElement);
    }

    private static void serializeLogout(Document document, Element rootElement,
                                        ClientMessage.Logout logout) {
        Element sessionElement = document.createElement("session");
        sessionElement.setTextContent(String.valueOf(logout.getSessionID()));
        rootElement.appendChild(sessionElement);
    }

    public static ClientMessage deserializeXml(String xml) throws Exception {
        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();

        // Create an InputSource from the XML string
        InputSource inputSource = new InputSource(new StringReader(xml));

        Document document = documentBuilder.parse(inputSource);

        Element rootElement = document.getDocumentElement();
        String commandName = rootElement.getAttribute("name");

        switch (commandName) {
            case "login" -> {
                Element nameElement = (Element) rootElement.getElementsByTagName("name").item(0);
                String userName = nameElement.getTextContent();
                return new ClientMessage.LoginRequest(userName);
            }
            case "list" -> {
                Element sessionElement = (Element) rootElement.getElementsByTagName("session").item(0);
                int sessionID = Integer.parseInt(sessionElement.getTextContent());
                return new ClientMessage.ListMembers(sessionID);
            }
            case "message" -> {
                Element messageElement = (Element) rootElement.getElementsByTagName

("message").item(0);
                String messageText = messageElement.getTextContent();
                Element sessionElement = (Element) rootElement.getElementsByTagName("session").item(0);
                int sessionID = Integer.parseInt(sessionElement.getTextContent());
                return new ClientMessage.Message(sessionID, messageText);
            }
            case "logout" -> {
                Element sessionElement = (Element) rootElement.getElementsByTagName("session").item(0);
                int sessionID = Integer.parseInt(sessionElement.getTextContent());
                return new ClientMessage.Logout(sessionID);
            }
            default -> throw new IllegalArgumentException("Invalid XML structure.");
        }
    }

    // ... existing code ...

    public static void main(String[] args) throws Exception {
        // Example usage: Serialize and deserialize a ClientMessage
        ClientMessage message = new ClientMessage.LoginRequest("USER_NAME");
        String serializedXml = serialize(message);
        System.out.println("Serialized XML: " + serializedXml);

        ClientMessage deserializedMessage = deserializeXml(serializedXml);
        System.out.println("Deserialized Message: " + deserializedMessage);
    }
}
```

You can run the `main` method to see an example of serializing and deserializing a `ClientMessage` object. Adjust the example as needed for other types of messages.