iDempiere Technical: Achieving Sub-Second Real-Time Updates with OSGi EventAdmin

package tw.ninniku.mrp.util;

import java.util.HashMap;
import java.util.Map;
import org.adempiere.base.event.EventManager;
import org.osgi.service.event.Event;

public class MESBroadcastUtil {
    // Define Event Topic
    public static final String TOPIC_MES_UPDATE = "idempiere/mes/update";
    public static final String PROPERTY_ORDER_ID = "M_Production_ID";
    public static final String PROPERTY_QTY = "Qty";

    /**
     * Send event to the OSGi System Bus
     * sendEvent = Synchronous delivery (Recommended for real-time updates)
     * postEvent = Asynchronous delivery
     */
    public static void publishMESUpdate(int orderId, int qty) {
        Map<String, Object> properties = new HashMap<>();
        properties.put(PROPERTY_ORDER_ID, orderId);
        properties.put(PROPERTY_QTY, qty);
        Event event = new Event(TOPIC_MES_UPDATE, properties);
        EventManager.getInstance().sendEvent(event);
    }
}

@Override
protected boolean afterSave(boolean newRecord, boolean success) {
    if (success) {
        // Send real-time update event
        MESBroadcastUtil.publishMESUpdate(get_ID(), 0);
    }
    return super.afterSave(newRecord, success);
}

package tw.ninniku.mrp.webui.form;

import org.adempiere.base.event.EventManager;
import org.adempiere.webui.panel.ADForm;
import org.adempiere.webui.panel.IFormController;
import org.osgi.service.event.EventHandler;
import org.zkoss.zk.ui.Desktop;
import org.zkoss.zk.ui.Executions;
import org.zkoss.zk.ui.event.Event;
import org.zkoss.zk.ui.event.EventListener;
import org.zkoss.zul.Hlayout;
import tw.ninniku.mrp.util.MESBroadcastUtil;

public abstract class AbstractKanbanForm extends ADForm 
        implements IFormController, EventListener<Event> {

    protected Hlayout mainLayout = new Hlayout();
    private EventHandler subscriber;
    
    /** Subclass must implement: Returns Kanban name for Debugging */
    protected abstract String getKanbanName();
    
    /** Subclass must implement: Refreshes Kanban content */
    protected abstract void refreshKanban();
    
    /**
     * Crucial! Enable Server Push when the page is attached.
     */
    @Override
    public void onPageAttached(org.zkoss.zk.ui.Page newpage, 
                               org.zkoss.zk.ui.Page oldpage) {
        super.onPageAttached(newpage, oldpage);
        if (newpage != null) {
            newpage.getDesktop().enableServerPush(true);
        }
    }
    
    @Override
    protected void initForm() {
        mainLayout.setHflex("1");
        mainLayout.setVflex("1");
        this.appendChild(mainLayout);

        // Render UI immediately
        refreshKanban();

        // Subscribe to real-time update events
        subscribeToEvents();
    }
    
    /**
     * Subscribe to OSGi EventAdmin events
     */
    private void subscribeToEvents() {
        try {
            // Get current Desktop and enable Server Push
            final Desktop myDesktop = Executions.getCurrent().getDesktop();
            myDesktop.enableServerPush(true);

            subscriber = new EventHandler() {
                @Override
                public void handleEvent(final org.osgi.service.event.Event event) {
                    // Check event topic
                    if (MESBroadcastUtil.TOPIC_MES_UPDATE.equals(event.getTopic())) {
                        // Check if Desktop is still alive
                        if (myDesktop.isAlive()) {
                            try {
                                // Use Executions.schedule to bridge to the ZK UI thread
                                Executions.schedule(myDesktop,
                                    new EventListener<Event>() {
                                        public void onEvent(Event evt) {
                                            // UI Safe Zone - UI can be updated here
                                            refreshKanban();
                                        }
                                    }, new Event("updateKanban"));
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            };

            // Register event listener
            EventManager.getInstance().register(
                MESBroadcastUtil.TOPIC_MES_UPDATE, subscriber);

            // Important! Prevent memory leaks - Unregister when component detaches
            this.addEventListener("onDetach", (event) -> {
                EventManager.getInstance().unregister(subscriber);
            });
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    @Override
    public ADForm getForm() {
        return this;
    }
}

public class WLabKanban extends AbstractKanbanForm {
    
    @Override
    protected String getKanbanName() {
        return "LabKanban";
    }

    @Override
    protected void refreshKanban() {
        mainLayout.getChildren().clear();
        // Rebuild UI components...
    }
}

Executions.schedule(desktop, 
    new EventListener<Event>() {
        public void onEvent(Event evt) {
            // Update UI here
        }
    }, new Event("eventName"));

Import-Package: 
 org.adempiere.base.event,
 org.adempiere.webui.component,
 org.adempiere.webui.panel,
 org.osgi.service.event;version="[1.4,2)",
 org.zkoss.zk.ui,
 org.zkoss.zk.ui.event,
 org.zkoss.zul,
 ...