Deregister UI remote event push strategy from application context (#1022)

* deregister UI remote event push strategy from application context
* remove application context from holder after detaching the UI

Signed-off-by: Bogdan Bondar <Bogdan.Bondar@bosch.io>

hawkbit-ui/src/main/java/org/eclipse/hawkbit/ui/AbstractHawkbitUI.java

@@ -23,6 +23,8 @@ import org.eclipse.hawkbit.ui.utils.VaadinMessageSource;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.support.AbstractApplicationContext;
 import org.vaadin.spring.events.EventBus.UIEventBus;
 
 import com.vaadin.annotations.Theme;
@@ -100,6 +102,21 @@ public abstract class AbstractHawkbitUI extends UI implements DetachListener {
 
         if (pushStrategy != null) {
             pushStrategy.clean();
+            clearContextListener();
+        }
+
+        SpringContextHelper.clearContext();
+    }
+
+    private void clearContextListener() {
+        if (pushStrategy instanceof ApplicationListener && context instanceof AbstractApplicationContext) {
+            final ApplicationListener<?> listener = (ApplicationListener<?>) pushStrategy;
+            ((AbstractApplicationContext) context).getApplicationListeners().remove(listener);
+
+            // we do not need to explicitly remove the listener from
+            // ApplicationEventMulticaster because it is done by
+            // UIBeanStore#destroy delegating to
+            // ApplicationListenerDetector#postProcessBeforeDestruction
         }
     }
 

hawkbit-ui/src/main/java/org/eclipse/hawkbit/ui/push/DelayedEventBusPushStrategy.java

@@ -131,6 +131,9 @@ public class DelayedEventBusPushStrategy
         LOG.debug("Cleanup delayed event push strategy for UI {}", vaadinUI.getUIId());
         jobHandle.cancel(true);
         queue.clear();
+
+        jobHandle = null;
+        vaadinUI = null;
     }
 
     private final class DispatchRunnable implements Runnable {

hawkbit-ui/src/main/java/org/eclipse/hawkbit/ui/utils/SpringContextHelper.java

@@ -12,9 +12,6 @@ import org.springframework.context.ApplicationContext;
 
 /**
  * Singleton for the spring application context.
- *
- *
- *
  */
 public final class SpringContextHelper {
 
@@ -27,6 +24,12 @@ public final class SpringContextHelper {
         // Utility class
     }
 
+    /**
+     * method to set application context.
+     * 
+     * @param context
+     *            ApplicationContext
+     */
     public static void setContext(final ApplicationContext context) {
         SpringContextHelper.context = context;
     }
@@ -70,4 +73,11 @@ public final class SpringContextHelper {
         return context.getBean(beanName, beanClazz);
     }
 
+    /**
+     * method to clear application context.
+     * 
+     */
+    public static void clearContext() {
+        context = null;
+    }
 }

hawkbit-ui/src/main/resources/hawkbit-ui-defaults.properties

@@ -12,6 +12,7 @@ vaadin.servlet.productionMode=true
 vaadin.servlet.urlMapping=/UI/*
 vaadin.servlet.heartbeatInterval=60
 vaadin.servlet.closeIdleSessions=false
+server.servlet.session.timeout=300
 
 hawkbit.server.ui.links.documentation.root=https://www.eclipse.org/hawkbit/
 hawkbit.server.ui.links.documentation.security=https://www.eclipse.org/hawkbit/concepts/authorization/