Added initial sketch of JSON codec abstraction and related codec tracking service.
diff --git a/core/api/src/main/java/org/onlab/onos/codec/CodecService.java b/core/api/src/main/java/org/onlab/onos/codec/CodecService.java
new file mode 100644
index 0000000..c6dbda2
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+++ b/core/api/src/main/java/org/onlab/onos/codec/CodecService.java
@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.onlab.onos.codec;
+
+import java.util.Set;
+
+/**
+ * Service for registering and retrieving JSON codecs for various entities.
+ */
+public interface CodecService {
+
+ /**
+ * Returns the set of classes with currently registered codecs.
+ *
+ * @return set of entity classes
+ */
+ Set<Class<?>> getCodecs();
+
+ /**
+ * Returns the JSON codec for the specified entity class.
+ *
+ * @param entityClass entity class
+ * @return JSON codec; null if no codec available for the class
+ */
+ JsonCodec getCodec(Class<?> entityClass);
+
+ /**
+ * Registers the specified JSON codec for the given entity class.
+ *
+ * @param entityClass entity class
+ * @param codec JSON codec
+ */
+ void registerCodec(Class<?> entityClass, JsonCodec codec);
+
+ /**
+ * Unregisters the JSON codec for the specified entity class.
+ *
+ * @param entityClass entity class
+ */
+ void unregisterCodec(Class<?> entityClass);
+
+}