如何在 Vaadin 8 中绑定外键

Question

我无法解决问题。我有一个 window 和 TextField，我想绑定一个外键，但不知道我做错了什么。我已经在这里阅读了答案：我决定使用Converter，但还是跌跌撞撞。因此，有两个实体（简化）：Client 和 Order。现有或新客户可以有多个订单，意味着 Order.clientID 是外键

客户实体：

@Entity
@DynamicInsert
@DynamicUpdate
@Table(name = "Clients")
public class Client {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "ClientID", updatable = false, nullable = false)
    private Long clientID;

    @Column(name = "Name", nullable = false, length = 20)
    private String name;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "clientID")
    private Set<Order> orders;

    public Long getId() { return clientID; }

    public void setId(Long clientID) { this.clientID = clientID; }

    public String getName() { return firstName; }

    public void setName(String name) { this.name = name; }
}

订单实体：

@Entity
@DynamicInsert
@DynamicUpdate
@Table(name = "Orders")
public class Order{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "OrderID", nullable = false)
    private Long orderID;

    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "ClientID",
            referencedColumnName = "ClientID",
            updatable = false,
            nullable = false)
    private Client clientID;

    @Column(name = "Description", nullable = false, length = 1000)
    private String description;

    public Long getOrderID() { return orderID; }

    //public Long getClientID() { return clientID.getId(); }

    public Client getClientID() { return clientID; }

    public void setClientID(Client clientID) { this.clientID = clientID; }

    public String getDescription() { return description; }

    public void setDescription(String description) { this.description = description; }

}

并且我想将 Order.clientID 绑定到 TextField。但是 IDEA 将 setter setClientID 突出显示为 "Cannot resolve method 'setClientID'"

public class AddOrderModalView extends Window {

    private OrderService orderService = new OrderService();
    private Order order = new Order();

    Binder<Order> binder = new Binder<>(Order.class);
    private ChangeHandler changeHandler = new ChangeHandler() {
        @Override
        public void onChange() {

        }
    };

    private FormLayout formLayout = new FormLayout();
    private TextField clientId = new TextField("Client ID");
    private TextField description = new TextField("Description");
    private Button save = new Button("Save");
    private Button cancel = new Button("Cancel");

    public AddOrderModalView() {
        super("Add a new order");

        VerticalLayout subContent = new VerticalLayout();
        subContent.setSizeFull();

        HorizontalLayout actions = new HorizontalLayout();
        actions.addComponents(save, cancel);

        formLayout.addComponents(clientId, description);

        subContent.addComponent(formLayout);
        setContent(subContent);

        save.addStyleNames(ValoTheme.BUTTON_SMALL, ValoTheme.BUTTON_PRIMARY);
        cancel.addStyleName(ValoTheme.BUTTON_SMALL);

        save.addClickListener(e -> save());
        cancel.addClickListener(e -> close());

        bindingFields();

        setModal(true);
    }

    private void bindingFields() {
        binder.forField(clientId)
                .withConverter(Long::valueOf, String::valueOf)
                .bind(Order::getClientID, Order::setClientID); //the error is here

        binder.forField(this.description)
                .withValidator(new StringLengthValidator(
                        "Please add description. The maximum length is 1000 characters", 1, 1000))
                .bind(Order::getDescription, Order::setDescription);

        binder.bindInstanceFields(this);

        binder.setBean(order);
    }

    public interface ChangeHandler {
        void onChange();
    }

    private void save() {
        if (binder.validate().isOk()) {
            orderService.persist(order);
            close();
            changeHandler.onChange();
        }
    }
}

ClientToClientIdConverter:

public class ClientToClientIdConverter implements Converter<String, Client> {
    @Override
    public Result<Client> convertToModel(String s, ValueContext valueContext) {
        return Result.error("not supported");
    }

    @Override
    public String convertToPresentation(Client client, ValueContext valueContext) {
        return Objects.toString(client.getId(), "");
    }
}

谁能帮我解决这个问题？

Answer 1

您的绑定不起作用，因为您的 setClient 方法需要一个 Client 类型的对象作为参数，而不是 Long。您应该将其更改为：

public void setClientID(Long clientID) { this.clientID = clientID; }

您也可以使用组合框来选择客户，在 Vaadin 网站上有一个如何将对象绑定到组合框的示例。

Answer 2

问题的答案：如何在文本字段中绑定外键（或任何其他嵌套属性）（不是您需要的！）

您可以通过提供 lambda 表达式来获取和设置嵌套属性来实现。

TextField clientId = new TextField("Client ID");
binder.forField(clientId)
    .withConverter(new StringToLongConverter("error message"))
    .bind(item -> item.getClient().getId(), (item, value) -> item.getClient().setId(value));

如果此时订单没有客户端，则此代码可能会导致 NullPointerExceptions。如果可能，则改用它（添加了对空值的检查）：

TextField clientId = new TextField("Client ID");
binder.forField(clientId)
    .withConverter(new StringToLongConverter("error message"))
    .bind(
        item -> item.getClient() != null ? item.getClient.getId() : null,
        (item, value) -> {
                if(item.getClient() != null){
                    item.getClient().setId(value);
                }
    });

警告！请注意，手动更改此文本字段中的值将更改已分配给它的客户端的 ID，并且不是 select/assign 此订单的新客户。如果您想要后者，请改用 ComboBox！我不确定做第一个是否有意义，但我回答是因为你问了。我现在确定你想要后一种选择，所以请继续下一部分。

你问题的实际解决方案：看来你确实需要一个ComboBox，因为你想select/assign订单的客户。

所以你基本上需要的是：

ComboBox<Client> clientSelection = new ComboBox<Client>("client");

clientSelection.setItems(clientService.findAll()); // list/set of possible clients.

// Using clients name for item captions now, but you can also use id or both
clientSelection.setItemCaptionGenerator(Client::getName); 

binder.forField(clientSelection)
            .bind(Order::getClient, Order::setClient);

这样，您可以 select 一个客户端，然后将其设置为绑定订单客户端。

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