Option to ignore duplicate alarms

setup/default.xml

@@ -19,6 +19,7 @@
     <entry key='logger.file'>./logs/tracker-server.log</entry>
 
     <entry key='event.enable'>true</entry>
+    <entry key='event.ignoreDuplicateAlerts'>true</entry>
     <entry key='processing.computedAttributes.enable'>true</entry>
 
     <entry key='media.path'>./media</entry>

src/org/traccar/events/AlertEventHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 Anton Tananaev ([email protected])
+ * Copyright 2016 - 2018 Anton Tananaev ([email protected])
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,18 +19,34 @@
 import java.util.Map;
 
 import org.traccar.BaseEventHandler;
+import org.traccar.Context;
 import org.traccar.model.Event;
 import org.traccar.model.Position;
 
 public class AlertEventHandler extends BaseEventHandler {
 
+    private final boolean ignoreDuplicateAlerts;
+
+    public AlertEventHandler() {
+        ignoreDuplicateAlerts = Context.getConfig().getBoolean("event.ignoreDuplicateAlerts");
+    }
+
     @Override
     protected Map<Event, Position> analyzePosition(Position position) {
         Object alarm = position.getAttributes().get(Position.KEY_ALARM);
         if (alarm != null) {
-            Event event = new Event(Event.TYPE_ALARM, position.getDeviceId(), position.getId());
-            event.set(Position.KEY_ALARM, (String) alarm);
-            return Collections.singletonMap(event, position);
+            boolean ignoreAlert = false;
+            if (ignoreDuplicateAlerts) {
+                Position lastPosition = Context.getIdentityManager().getLastPosition(position.getDeviceId());
+                if (lastPosition != null && alarm.equals(lastPosition.getAttributes().get(Position.KEY_ALARM))) {
+                    ignoreAlert = true;
+                }
+            }
+            if (!ignoreAlert) {
+                Event event = new Event(Event.TYPE_ALARM, position.getDeviceId(), position.getId());
+                event.set(Position.KEY_ALARM, (String) alarm);
+                return Collections.singletonMap(event, position);
+            }
         }
         return null;
     }