Implemented the extension framework for selectors.
Change-Id: I577900141889fc70ca54e96cd5d54cfd5194b05d
diff --git a/core/api/src/main/java/org/onosproject/net/flow/Extension.java b/core/api/src/main/java/org/onosproject/net/flow/Extension.java
new file mode 100644
index 0000000..1d61542
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/flow/Extension.java
@@ -0,0 +1,71 @@
+/*
+ * Copyright 2015 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.
+ */
+
+package org.onosproject.net.flow;
+
+import org.onosproject.net.flow.instructions.ExtensionPropertyException;
+
+import java.util.List;
+
+/**
+ * An extension to the northbound APIs.
+ */
+public interface Extension {
+
+ /**
+ * Sets a property on the extension.
+ *
+ * @param key property key
+ * @param value value to set for the given key
+ * @param <T> class of the value
+ * @throws ExtensionPropertyException if the given key is not a valid
+ * property on this extension
+ */
+ <T> void setPropertyValue(String key, T value) throws ExtensionPropertyException;
+
+ /**
+ * Gets a property value of an extension.
+ *
+ * @param key property key
+ * @param <T> class of the value
+ * @return value of the property
+ * @throws ExtensionPropertyException if the given key is not a valid
+ * property on this extension
+ */
+ <T> T getPropertyValue(String key) throws ExtensionPropertyException;
+
+ /**
+ * Gets a list of all properties on the extension.
+ *
+ * @return list of properties
+ */
+ List<String> getProperties();
+
+ /**
+ * Serialize the extension to a byte array.
+ *
+ * @return byte array
+ */
+ byte[] serialize();
+
+ /**
+ * Deserialize the extension from a byte array. The properties
+ * of this object will be overwritten with the data in the byte array.
+ *
+ * @param data input byte array
+ */
+ void deserialize(byte[] data);
+}