如何在vaadin中动态推送更新页面？

Question

我有一个使用Vaadin和Spring (+Security)的工作应用程序。我现在正尝试使用vaadin-push动态地将更新推送到客户端接口。

我想要创建一个对所有客户端都一样的“视图”。视图应该通过push获得一个动态递增的计数器。因此，当客户端显示页面时，计数器会自我更新(或者在我的示例中:向页面追加多个标签组件)。每个客户都应该看到相同的值。

但我没有看到这些变化被推到网页上。为什么？

//the static controller the dynamically changes content
@Controller
public class ViewPresenter {
    private static int counter = 0;

    @Autowired
    private void StaticView view;

    @Scheduled(fixedRate = 1000)
    public void refresh() {
        //push the content change periodically to frontend
        view.getUI().access(new Runnable() {
            @Override
            public void run() {
                view.addComponent(new Label("refresh: " + counter++);
                Sysout("update executed: " + counter); //OK, is printed
            }
        });
    }
}

//the static test component that gets a new label added on every content change
@VaadinComponent
public class StaticView extends CssLayout {
        //this is the view that every client should see
}

//the secured admin view
@VaadinView(name = "/secured")
@Scope("ui")
@Secured("user")
public class SecuredView extends VerticalLayout implements View {
    @Autowired
    private StaticView staticView;

    @Override
    public void enter(ViewChangeEvent event) {
        addComponent(staticView);
    }
}

//enable push
@Configuration
@Push
public class AppConfig {
}

@VaadinUI
@PreserveOnRefresh
public class ApplicationUI extends UI {

} 

只有当我手动刷新网页时，我才能在客户端看到更改。但是内容本身不会自动改变。

也许@Push必须放在UI类上？但在这种情况下，我会得到以下错误：

java.lang.IllegalStateException:不能挂起超过会话超时的响应。在org.atmosphere.cpr.AtmosphereResourceImpl.suspend(AtmosphereResourceImpl.java:314) at org.atmosphere.cpr.AtmosphereResourceImpl.suspend(AtmosphereResourceImpl.java:292) at com.vaadin.server.communication.PushHandler$2.run(PushHandler.java:129) at com.vaadin.server.communication.PushHandler.callWithUi(PushHandler.java:242) at com.vaadin.server.communication.PushHandler.access$200(PushHandler.java:55)在web.xml中增加会话超时的值com.vaadin.server.communication.PushHandler$1.onRequest(PushHandler.java:73)

Answer 1

基于https://github.com/peholmst/vaadin4spring/issues/51#issuecomment-46875255的解决方案

server.sessionTimeout=30与@Push(transport = Transport.LONG_POLLING)