JavaFX - MVC应用程序与数据库的最佳实践 [英] JavaFX - MVC Application best practices with database

问题描述

我是JavaFX的新手，我想知道用这种语言开发MVC数据库应用程序的最佳做法是什么，我认为如果你是一名高级开发人员，我的问题会非常简单。

I'm new to JavaFX and I was wondering what are the best practices in this language to develop a MVC database application, I think my question will be pretty simple if you are an senior developer.

让我们考虑一个在JavaFX中开发的基本应用程序的简单示例：与SQL数据库链接的ToDoList。

Let us consider a simple example of a basic application developed in JavaFX : a ToDoList linked with a SQL Database.

• 数据库只是一个表任务，其中包含 id 和 taskDescr VARCHAR字段。


• 目的很简单：我们只想在TableView或ListView中显示任务，并能够添加一些任务。

• The database is just one table Task with an id and a taskDescr VARCHAR field.
• The purpose is pretty easy : we just want to display the task in a TableView or ListView and be able to add some tasks.

这是我们的应用程序是什么样的：

That's what our application looks like :

ToDoList GUI

我决定将代码分为四个部分， DAO ，用于表示表中数据的类（任务。 java），访问数据库的DAO类（它的行为不是m在这里）。代表我们TodoList的Model部分的模型（包含任务和执行操作的列表，调用DAO等）。 FXML 观看次数和控制器：

I decided to split my code into four parts, DAO for the classes who represents datas in the table (Task.java), the DAO class who access the database (its behavior does not matter here). The model who represents the Model part of our TodoList (containing a list of task and performing operations on it, calling the DAO, etc..). The FXML Views and the Controller :

项目结构

接下来，您可以找到我们感兴趣的不同类的代码（我们认为DAO没问题（自动设置id）我们不处理错误情况以简化代码：

Next, you can find the code of the different classes that interest us (We supposed that the DAO is OK (setting id automatically) an we do not handle error cases to simplify code :

Task.java

public class Task {

    private int id;
    private SimpleStringProperty task;

    public Task(int i, String s){
        this.id = i;
        this.task = new SimpleStringProperty(s);
    }

    public void setId(int i){
        this.id = i;
    }

    public int getId() {
        return id;
    }

    public String getTask() {
        return task.get();
    }

    public void setTask(String task) {
        this.task.set(task);
    }

    @Override
    public boolean equals(Object o){
        if(this.id == ((Task)o).id)
            return true;
        return false;
    }
}

ToDoListModel.java

public class ToDoListModel {

    private List<Task> taskList;
    private DAO dao;

    public ToDoListModel(){
        this.taskList = new ArrayList<Task>();
        this.dao = new DAO();
    }

    public void loadDatabase(){
        this.taskList = this.dao.getAllTasks();
    }

    public void addTask(Task t){
        // Operations throwing Exceptions such as : Does the task t is already in the list, etc...
        this.taskList.add(t);
        this.dao.createTask(t);
    }

    public void deleteTask(Task t){
        this.taskList.remove(t);
        this.dao.deleteTask(t);
    }

    public List<Task> getTaskList() {
        return taskList;
    }
}

Controller.java

public class Controller {

    private final ToDoListModel model;

    @FXML
    private TableView<Task> taskTable;
    @FXML
    private TableColumn<Task, String> taskColumn;
    @FXML
    private TextField taskTextField;

    public Controller(ToDoListModel m){
        this.model = m;
    }

    @FXML
    protected void initialize() {
        this.model.loadDatabase();

        // Setting up data table
        taskColumn.setCellValueFactory(new PropertyValueFactory<Task, String>("task"));
        ObservableList<Task> taskObservableList = FXCollections.observableList(this.model.getTaskList());
        taskTable.setItems(taskObservableList);
    }

    @FXML
    public void handleAddButton(ActionEvent e) {
        Task t = new Task(-1, this.taskTextField.getText());

        // What operations to do here ?
        this.model.addTask(t);
        this.taskTable.getItems().add(t);
        this.taskTable.refresh();
    }

}

Main.java

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        ToDoListModel model = new ToDoListModel();
        primaryStage.setTitle("My Todo");
        FXMLLoader loader = new FXMLLoader();
        loader.setLocation(getClass().getResource("views/View.fxml"));
        loader.setController(new Controller(model));
        Parent root = loader.load();
        primaryStage.setScene(new Scene(root));
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

最后，我的问题是：我的做法好吗？我的意思是我创建了一个带有任务列表的ToDoListModel这一事实，我在同一任务中更新了对象列表任务我使用DAO更新了我的数据库（在DAO将在列表中添加后执行）并且最重要的是：我应该在Controller的 handleAddButton 中执行哪些操作？这里我首先使用了我的TodoListModel中的add方法，但这还不够，因为我的可观察列表被错误地更新了（添加的任务出现但我们无法用鼠标选择它）。然后，当我在TableView项中添加它时，任务出现两次并在列表中添加了两次。

Finally, my question is : Is my approach good ? I mean the fact that I've created a ToDoListModel with a list of task, the fact that I update my list of Objects Task at the same task I update my database with the DAO (a create in the DAO will be performed after an add in the list) and the most important : what operations should I do in the handleAddButton of my Controller ? Here I used first the add method in my TodoListModel but it's not enough because my observable list is wrongly updated (The added task appears but we can not select it with the mouse). Then, when I add it also in the TableView items, the Task appears twice and has been added twice in the list.

结果我明白了ObservableList链接到我在ToDoListModel中的List但如果我只想在我的模型中对该列表进行操作但是正确更新ObservableList，我应该怎么做？ （可选项目等...）

As a result I've understood that the ObservableList was linked to the List I have in my ToDoListModel but what am I supposed to do if I want to do operations on that list only in my model but getting the ObservableList updated correctly ? (Selectable item etc...)

复制示例

提前感谢您的帮助和耐心，
此致
Paul

Thank you in advance for your help and your patience, Sincerely, Paul

推荐答案

以下是一个示例实现

DAO 类负责连接到数据库（可能使用池或其他）。在这种情况下，它进行简单连接。

Here is an example implementation
The DAO class takes care of connecting to the database (may use a pool or something else). In this case, it makes a simple connection.

public class DAO {
    public Connection getConnection() throws SQLException {
        return  DriverManager.getConnection("jdbc:mysql://192.168.40.5:3306/test", "root", "");
    }
}

ToDoListModel class通过使用 DAO 的实例来处理数据库，以获得有效的连接。

The ToDoListModel class takes care of working with the database by using an instance of DAO to get a valid connection.

public class ToDoListModel {
    private DAO dao;

    public static ToDoListModel getInstance() {
        ToDoListModel model = new ToDoListModel();
        model.dao = new DAO();

        return model;
    }

    private ToDoListModel() {
    }

    public void addTask(Task task) throws SQLException {
        try(Connection connection = dao.getConnection()) {
            String q = "insert into todo (name) values (?)";

            try(PreparedStatement statement = connection.prepareStatement(q, Statement.RETURN_GENERATED_KEYS)) {
                statement.setString(1, task.getName());
                statement.executeUpdate();

                try(ResultSet rs = statement.getGeneratedKeys()) {
                    if(rs.next()) {
                        task.setId(rs.getInt(1));
                    }
                }
            }
        }
    }

    public void deleteTask(Task task) throws SQLException {
        try(Connection connection = dao.getConnection()) {
            String q = "delete from todo where id = ?";

            try(PreparedStatement statement = connection.prepareStatement(q)) {
                statement.setInt(1, task.getId());
                statement.executeUpdate();
            }
        }
    }

    public ObservableList<Task> getTaskList() throws SQLException {
        try(Connection connection = dao.getConnection()) {
            String q = "select * from todo";

            try(Statement statement = connection.createStatement()) {
                try(ResultSet rs = statement.executeQuery(q)) {
                    ObservableList<Task> tasks = FXCollections.observableArrayList();

                    while (rs.next()) {
                        Task task = new Task();
                        task.setId(rs.getInt("id"));
                        task.setName(rs.getString("name"));

                        tasks.add(task);
                    }

                    return tasks;
                }
            }
        }
    }
}

控制器使用 ToDoListModel 初始化 TableView 控件和添加操作（编辑和阅读 - 我没有实现因为我坚持你的代码）

The controller uses ToDoListModel to initialize TableView controls and add operations (editing and reading - I did not implement them because I stick to your code)

public class Controller {

    @FXML
    private TextField textField;

    @FXML
    private TableView<Task> tableView;

    @FXML
    private TableColumn<Task, String> nameTableColumn;

    @FXML
    private Button addButton;

    @FXML
    private void initialize() {
        nameTableColumn.setCellValueFactory(cdf -> cdf.getValue().nameProperty());

        addButton.disableProperty().bind(Bindings.isEmpty(textField.textProperty()));

        CompletableFuture.supplyAsync(this::loadAll)
            .thenAccept(list -> Platform.runLater(() -> tableView.getItems().setAll(list)))
            .exceptionally(this::errorHandle);
    }

    @FXML
    private void handleAddButton(ActionEvent event) {
        CompletableFuture.supplyAsync(this::addTask)
                .thenAccept(task -> Platform.runLater(() -> {
                    tableView.getItems().add(task);

                    textField.clear();
                    textField.requestFocus();
                }))
                .exceptionally(this::errorHandle);
    }

    private Task addTask() {
        try {
            Task task = new Task(textField.getText());
            ToDoListModel.getInstance().addTask(task);

            return task;
        }
        catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }

    private ObservableList<Task> loadAll() {
        try {
            return ToDoListModel.getInstance().getTaskList();
        }
        catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }

    private Void errorHandle(Throwable throwable) {
        throwable.printStackTrace();
        return null;
    }
}

任何数据库操作都与 CompletableFuture 但您可以使用您喜欢的任何内容。重要的是要记住UI线程只能由它做出唯一的。

Any database operations are asynchronous with CompletableFuture but you can use whatever you prefer. The important thing is to remember that UI threads can only be made uniquely by it.

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