Async Push

Example code is available on github.com/vaadin-on-grails/async-push.

Push has been added in Vaadin plugin version 7.3.0.1. Make sure you have this, or later, version of the plugin.

Step 1

Enable anyc in VaadinConfig.groovy.

asyncSupported = true

Step 2

In order to demonstrate Vaadin push, we will create a view that will create a label that will have initial value that will be overriden by a thread. The thread will wait one second and then set other text into the label. Let's say, that we replace waiting by a call to external system, where we expect a delay.

For pusing another label, we create Pusher thread that will change text of the label.

package app.views.push

import app.MyUI
import com.vaadin.navigator.View
import com.vaadin.navigator.ViewChangeListener
import com.vaadin.ui.Label
import com.vaadin.ui.VerticalLayout

class PushView extends VerticalLayout implements View {

    static final String VIEW_NAME = "push"

    Label loadingText = new Label("Loading UI, please wait...");

    @Override
    void enter(ViewChangeListener.ViewChangeEvent viewChangeEvent) {
        loadingText.setSizeUndefined();
        addComponent(loadingText);
        new Pusher().start();
    }

    class Pusher extends Thread {
        @Override
        public void run() {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
            }

            MyUI.current.access(new Runnable() {
                @Override
                public void run() {
                    loadingText.setValue("Done!")
                }
            });
        }
    }
}

Step 3

Add Push annotation on your UI class.

package app

import app.views.push.PushView
import com.vaadin.annotations.Push
import com.vaadin.navigator.Navigator
import com.vaadin.server.VaadinRequest
import com.vaadin.ui.UI

@Push
class MyUI extends UI {

    @Override
    protected void init(VaadinRequest vaadinRequest) {

        Navigator navigator = new Navigator(this, this)
        navigator.addView(PushView.VIEW_NAME, PushView)

        navigator.navigateTo(PushView.VIEW_NAME)
    }
}