adding Access device events and a listener

Change-Id: I0e9b4dae4231e7057443e7ed52723e29e06747cc
diff --git a/src/main/java/org/onosproject/olt/api/AccessDeviceEvent.java b/src/main/java/org/onosproject/olt/api/AccessDeviceEvent.java
new file mode 100644
index 0000000..212fd37
--- /dev/null
+++ b/src/main/java/org/onosproject/olt/api/AccessDeviceEvent.java
@@ -0,0 +1,88 @@
+package org.onosproject.olt.api;
+
+import org.onlab.packet.VlanId;
+import org.onosproject.event.AbstractEvent;
+import org.onosproject.net.DeviceId;
+
+import java.util.Optional;
+
+/**
+ * Describes an access device event.
+ */
+public class AccessDeviceEvent extends AbstractEvent<AccessDeviceEvent.Type, DeviceId> {
+
+    private final Optional<VlanId> sVlan;
+    private final Optional<VlanId> cVlan;
+
+    public enum Type {
+        /**
+         * A subscriber was registered and provisioned.
+         */
+        SUBSCRIBER_REGISTERED,
+
+        /**
+         * A subscriber was unregistered and deprovisioned.
+         */
+        SUBSCRIBER_UNREGISTERED,
+
+        /**
+         * An access device connected.
+         */
+        DEVICE_CONNECTED,
+
+        /**
+         * An access device disconnected.
+         */
+        DEVICE_DISCONNECTED
+
+    }
+
+    /**
+     *
+     * Creates an event of a given type and for the specified device,
+     * along with the cVlanId and sVlanId. The vlan fields may not be provisioned
+     * if the event is related to the access device (dis)connection.
+     *
+     * @param type the event type
+     * @param deviceId the device id
+     * @param sVlanId the service vlan
+     * @param cVlanId the customer vlan
+     */
+    public AccessDeviceEvent(Type type, DeviceId deviceId,
+                             VlanId sVlanId,
+                             VlanId cVlanId) {
+        super(type, deviceId);
+        this.sVlan = Optional.ofNullable(sVlanId);
+        this.cVlan = Optional.ofNullable(cVlanId);
+    }
+
+    /**
+     *
+     * Creates an event of a given type and for the specified device, and timestamp
+     * along with the cVlanId and sVlanId. The vlan fields may not be provisioned
+     * if the event is related to the access device (dis)connection.
+     *
+     * @param type the event type
+     * @param deviceId the device id
+     * @param time a timestamp
+     * @param sVlanId the service vlan
+     * @param cVlanId the customer vlan
+     */
+    protected AccessDeviceEvent(Type type, DeviceId deviceId, long time,
+                                VlanId sVlanId,
+                                VlanId cVlanId) {
+        super(type, deviceId, time);
+        this.sVlan = Optional.ofNullable(sVlanId);
+        this.cVlan = Optional.ofNullable(cVlanId);
+
+    }
+
+    public Optional<VlanId> sVlanId() {
+        return sVlan;
+    }
+
+    public Optional<VlanId> cVlanId() {
+        return cVlan;
+    }
+
+}
diff --git a/src/main/java/org/onosproject/olt/api/AccessDeviceListener.java b/src/main/java/org/onosproject/olt/api/AccessDeviceListener.java
new file mode 100644
index 0000000..f652a10
--- /dev/null
+++ b/src/main/java/org/onosproject/olt/api/AccessDeviceListener.java
@@ -0,0 +1,9 @@
+package org.onosproject.olt.api;
+
+import org.onosproject.event.EventListener;
+
+/**
+ * Entity capable of receiving access device related events.
+ */
+public interface AccessDeviceListener extends EventListener<AccessDeviceEvent> {
+}
diff --git a/src/main/java/org/onosproject/olt/api/package-info.java b/src/main/java/org/onosproject/olt/api/package-info.java
new file mode 100644
index 0000000..f99b4e7
--- /dev/null
+++ b/src/main/java/org/onosproject/olt/api/package-info.java
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * OLT event api.
+ */
+package org.onosproject.olt.api;