Adding a small hack to allow resolving model specific resources against the class-loader of the model.

Change-Id: I78dd29cd626495005cec094a8a6f1a952e3e68df
diff --git a/apps/yang/src/main/java/org/onosproject/yang/AbstractYangModelRegistrator.java b/apps/yang/src/main/java/org/onosproject/yang/AbstractYangModelRegistrator.java
index 094c1c2..d2ec54f 100644
--- a/apps/yang/src/main/java/org/onosproject/yang/AbstractYangModelRegistrator.java
+++ b/apps/yang/src/main/java/org/onosproject/yang/AbstractYangModelRegistrator.java
@@ -43,12 +43,17 @@
 
     private final Logger log = LoggerFactory.getLogger(getClass());
     private final Class<?> loaderClass;
-    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected YangModelRegistry modelRegistry;
+
     private Map<YangModuleId, AppModuleInfo> appInfo;
     protected YangModel model;
     private ModelRegistrationParam registrationParam;
 
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected YangModelRegistry modelRegistry;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected YangClassLoaderRegistry sourceResolver;
+
     /**
      * Creates a model registrator primed with the class-loader of the specified
      * class.
@@ -80,6 +85,7 @@
         ModelRegistrationParam.Builder b =
                 DefaultModelRegistrationParam.builder().setYangModel(model);
         registrationParam = getAppInfo(b).setYangModel(model).build();
+        sourceResolver.registerClassLoader(model.getYangModelId(), loaderClass.getClassLoader());
         modelRegistry.registerModel(registrationParam);
         log.info("Started");
     }
@@ -96,6 +102,7 @@
     @Deactivate
     protected void deactivate() {
         modelRegistry.unregisterModel(registrationParam);
+        sourceResolver.unregisterClassLoader(model.getYangModelId());
         log.info("Stopped");
     }
 }
diff --git a/apps/yang/src/main/java/org/onosproject/yang/YangClassLoaderRegistry.java b/apps/yang/src/main/java/org/onosproject/yang/YangClassLoaderRegistry.java
new file mode 100644
index 0000000..7198346
--- /dev/null
+++ b/apps/yang/src/main/java/org/onosproject/yang/YangClassLoaderRegistry.java
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2017-present 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.yang;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Auxiliary mechanism for resolving model IDs into class-loaders from where
+ * the model was registered.
+ */
+@Beta
+public interface YangClassLoaderRegistry {
+
+    /**
+     * Get the class loader registered for the given model id.
+     *
+     * @param modelId model identifier
+     * @return class loader registered for the model
+     */
+    ClassLoader getClassLoader(String modelId);
+
+    /**
+     * Register the class loader for the specified model.
+     *
+     * @param modelId     model identifier
+     * @param classLoader class loader
+     */
+    void registerClassLoader(String modelId, ClassLoader classLoader);
+
+    /**
+     * Register the class loader for the specified model.
+     *
+     * @param modelId model identifier
+     */
+    void unregisterClassLoader(String modelId);
+}
diff --git a/apps/yang/src/main/java/org/onosproject/yang/YangRuntimeManager.java b/apps/yang/src/main/java/org/onosproject/yang/YangRuntimeManager.java
index 063051b..c792dd8 100644
--- a/apps/yang/src/main/java/org/onosproject/yang/YangRuntimeManager.java
+++ b/apps/yang/src/main/java/org/onosproject/yang/YangRuntimeManager.java
@@ -53,7 +53,9 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -65,7 +67,7 @@
 @Component(immediate = true)
 public class YangRuntimeManager implements YangModelRegistry,
         YangSerializerRegistry, YangRuntimeService, ModelConverter,
-        SchemaContextProvider {
+        SchemaContextProvider, YangClassLoaderRegistry {
 
     private static final String APP_ID = "org.onosproject.yang";
     private final Logger log = LoggerFactory.getLogger(getClass());
@@ -79,6 +81,8 @@
     private DefaultModelConverter modelConverter;
     private DefaultSchemaContextProvider schemaContextProvider;
 
+    private Map<String, ClassLoader> classLoaders;
+
     @Activate
     public void activate() {
         coreService.registerApplication(APP_ID);
@@ -89,6 +93,7 @@
         serializerRegistry.registerSerializer(new JsonSerializer());
         serializerRegistry.registerSerializer(new XmlSerializer());
         modelConverter = new DefaultModelConverter(modelRegistry);
+        classLoaders = new ConcurrentHashMap<>();
         log.info("Started");
     }
 
@@ -174,4 +179,19 @@
     public RpcContext getRpcContext(ResourceId resourceId) {
         return schemaContextProvider.getRpcContext(resourceId);
     }
+
+    @Override
+    public ClassLoader getClassLoader(String modelId) {
+        return classLoaders.get(modelId);
+    }
+
+    @Override
+    public void registerClassLoader(String modelId, ClassLoader classLoader) {
+        classLoaders.put(modelId, classLoader);
+    }
+
+    @Override
+    public void unregisterClassLoader(String modelId) {
+        classLoaders.remove(modelId);
+    }
 }