@UIScope注释不适用于春天视图？

我正面临着Vaadin spring注释@UIScope的问题,定义如下：

@SpringComponent
@SpringView(name = AdminView.VIEW_NAME)
@UIScope
public class AdminView extends NavigatingView {
    ...
}

每次导航打开视图时都会创建视图.我希望它在第一次访问时只创建一次.

但是,如果我用@Scope(UIScopeImpl.VAADIN_UI_SCOPE_NAME)替换@UIScope,那么它会按预期工作.我错过了什么？

解决方法:

它与@SpringView和@UIScope注释的顺序有关,因为tutorial和较旧的wiki page简要建议：

// Pay attention to the order of annotations

这可能与注释的处理方式和时间有关.我没有深入研究Vaadin代码,但根据@SpringView javadoc,它默认将视图放入视图范围.此外,我认为您不需要@SpringComponent注释,因为您已经使用@SpringView将其注册为spring组件.

Annotation to be placed on View-classes that should be handled by the SpringViewProvider.

This annotation is also a stereotype annotation, so Spring will automatically detect the annotated classes. By default, this annotation also puts the view into the view scope. You can override this by using another scope annotation, such as the UI scope, on your view class. However, the singleton scope will not work!

在下面的示例中,您将找到2个视图,第一个视图的注释顺序正确,第二个视图与它们交换：

@SpringUI
@SpringViewDisplay
public class MyVaadinUI extends UI implements ViewDisplay {

    /* UI */

    private Panel springViewDisplay;

    @Override
    protected void init(VaadinRequest request) {
        VerticalLayout mainLayout = new VerticalLayout();
        HorizontalLayout buttonLayout = new HorizontalLayout();
        springViewDisplay = new Panel();

        buttonLayout.addComponent(new Button("1", event -> getNavigator().navigateTo(FirstView.VIEW_NAME)));
        buttonLayout.addComponent(new Button("2", event -> getNavigator().navigateTo(SecondView.VIEW_NAME)));
        mainLayout.addComponents(buttonLayout, springViewDisplay);
        setContent(mainLayout);

    }

    @Override
    public void showView(View view) {
        springViewDisplay.setContent((Component) view);
    }


    /* VIEWS */

    @UIScope
    @SpringView(name = FirstView.VIEW_NAME)
    public static class FirstView extends HorizontalLayout implements View {

        public static final String VIEW_NAME = "";

        @PostConstruct
        private void init() {
            System.out.println("Created first view");
            addComponent(new Label("First view - " + LocalDateTime.now()));
        }

        @Override
        public void enter(ViewChangeListener.ViewChangeEvent event) {
            // no-op
        }
    }

    @SpringView(name = SecondView.VIEW_NAME)
    @UIScope
    public static class SecondView extends HorizontalLayout implements View {

        public static final String VIEW_NAME = "secondView";

        @PostConstruct
        private void init() {
            System.out.println("Created second view");
            addComponent(new Label("Second view - " + LocalDateTime.now()));
        }

        @Override
        public void enter(ViewChangeListener.ViewChangeEvent event) {
            // no-op
        }
    }
}

正如您在下面的动画中所注意到的,当导航到第二个视图时,总是会创建一个新实例,而导航到第一个实例将重用初始实例：

标签：spring,vaadin8
来源： https://codeday.me/bug/20190823/1699820.html