Refactoring abstract driver loader to assure that default drivers get loaded first by default.

Change-Id: I2fd213d8f49b6390ec8f005795bb95661aaee793
diff --git a/core/api/src/main/java/org/onosproject/net/driver/AbstractDriverLoader.java b/core/api/src/main/java/org/onosproject/net/driver/AbstractDriverLoader.java
index e68eb99..7899d0c 100644
--- a/core/api/src/main/java/org/onosproject/net/driver/AbstractDriverLoader.java
+++ b/core/api/src/main/java/org/onosproject/net/driver/AbstractDriverLoader.java
@@ -15,27 +15,19 @@
  */
 package org.onosproject.net.driver;
 
-import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
-import org.apache.felix.scr.annotations.Deactivate;
 import org.apache.felix.scr.annotations.Reference;
 import org.apache.felix.scr.annotations.ReferenceCardinality;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 /**
- * Abstract boot-strapper for loading and registering driver definitions.
+ * Abstract bootstrapper for loading and registering driver definitions that
+ * are dependent on the default driver definitions.
  */
 @Component
-public abstract class AbstractDriverLoader {
-
-    private final Logger log = LoggerFactory.getLogger(getClass());
-
-    private DriverProvider provider;
-    private final String path;
+public abstract class AbstractDriverLoader extends AbstractIndependentDriverLoader {
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected DriverAdminService driverAdminService;
+    protected DefaultDriverProviderService defaultDriverProviderService;
 
     /**
      * Creates a new loader for resource with the specified path.
@@ -43,25 +35,7 @@
      * @param path drivers definition XML resource path
      */
     protected AbstractDriverLoader(String path) {
-        this.path = path;
-    }
-
-    @Activate
-    protected void activate() {
-        try {
-            provider = new XmlDriverLoader(getClass().getClassLoader(), driverAdminService)
-                    .loadDrivers(getClass().getResourceAsStream(path), driverAdminService);
-            driverAdminService.registerProvider(provider);
-        } catch (Exception e) {
-            log.error("Unable to load {} driver definitions", path, e);
-        }
-        log.info("Started");
-    }
-
-    @Deactivate
-    protected void deactivate() {
-        driverAdminService.unregisterProvider(provider);
-        log.info("Stopped");
+        super(path);
     }
 
 }
diff --git a/core/api/src/main/java/org/onosproject/net/driver/AbstractIndependentDriverLoader.java b/core/api/src/main/java/org/onosproject/net/driver/AbstractIndependentDriverLoader.java
new file mode 100644
index 0000000..c8f6f17
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/driver/AbstractIndependentDriverLoader.java
@@ -0,0 +1,68 @@
+/*
+ * 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.net.driver;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Abstract bootstrapper for loading and registering driver definitions that
+ * are independent from the default driver definitions.
+ */
+@Component
+public abstract class AbstractIndependentDriverLoader {
+
+    private final Logger log = LoggerFactory.getLogger(getClass());
+
+    private DriverProvider provider;
+    private final String path;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected DriverAdminService driverAdminService;
+
+    /**
+     * Creates a new loader for resource with the specified path.
+     *
+     * @param path drivers definition XML resource path
+     */
+    protected AbstractIndependentDriverLoader(String path) {
+        this.path = path;
+    }
+
+    @Activate
+    protected void activate() {
+        try {
+            provider = new XmlDriverLoader(getClass().getClassLoader(), driverAdminService)
+                    .loadDrivers(getClass().getResourceAsStream(path), driverAdminService);
+            driverAdminService.registerProvider(provider);
+        } catch (Exception e) {
+            log.error("Unable to load {} driver definitions", path, e);
+        }
+        log.info("Started");
+    }
+
+    @Deactivate
+    protected void deactivate() {
+        driverAdminService.unregisterProvider(provider);
+        log.info("Stopped");
+    }
+
+}
diff --git a/core/api/src/test/java/org/onosproject/net/driver/AbstractDriverLoaderTest.java b/core/api/src/test/java/org/onosproject/net/driver/AbstractDriverLoaderTest.java
index f91e629..f79b25b 100644
--- a/core/api/src/test/java/org/onosproject/net/driver/AbstractDriverLoaderTest.java
+++ b/core/api/src/test/java/org/onosproject/net/driver/AbstractDriverLoaderTest.java
@@ -44,7 +44,7 @@
         }
     }
 
-    protected AbstractDriverLoader loader;
+    protected AbstractIndependentDriverLoader loader;
 
     @Test
     public void testLoader() {
diff --git a/drivers/corsa/src/main/java/org/onosproject/drivers/corsa/CorsaDriversLoader.java b/drivers/corsa/src/main/java/org/onosproject/drivers/corsa/CorsaDriversLoader.java
index 33eb06e..b2ad9ee 100644
--- a/drivers/corsa/src/main/java/org/onosproject/drivers/corsa/CorsaDriversLoader.java
+++ b/drivers/corsa/src/main/java/org/onosproject/drivers/corsa/CorsaDriversLoader.java
@@ -17,23 +17,13 @@
 package org.onosproject.drivers.corsa;
 
 import org.apache.felix.scr.annotations.Component;
-import org.apache.felix.scr.annotations.Reference;
-import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.onosproject.net.driver.AbstractDriverLoader;
-import org.onosproject.net.driver.DefaultDriverProviderService;
 
 /**
  * Loader for Corsa device drivers.
  */
 @Component(immediate = true)
 public class CorsaDriversLoader extends AbstractDriverLoader {
-
-    //This reference is needed to enforce loading of the default drivers before
-    //the corsa drivers at ONOS startup if corsa.drivers is specified
-    //in the ONOS_APPS variable.
-    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    private DefaultDriverProviderService defaultDriverProviderService;
-
     public CorsaDriversLoader() {
         super("/corsa-drivers.xml");
     }
diff --git a/drivers/default/src/main/java/org/onosproject/driver/DefaultDriversLoader.java b/drivers/default/src/main/java/org/onosproject/driver/DefaultDriversLoader.java
index 12ee006..fbf41a4 100644
--- a/drivers/default/src/main/java/org/onosproject/driver/DefaultDriversLoader.java
+++ b/drivers/default/src/main/java/org/onosproject/driver/DefaultDriversLoader.java
@@ -18,7 +18,7 @@
 
 import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Service;
-import org.onosproject.net.driver.AbstractDriverLoader;
+import org.onosproject.net.driver.AbstractIndependentDriverLoader;
 import org.onosproject.net.driver.DefaultDriverProviderService;
 
 /**
@@ -26,7 +26,8 @@
  */
 @Service
 @Component(immediate = true)
-public class DefaultDriversLoader extends AbstractDriverLoader implements DefaultDriverProviderService {
+public class DefaultDriversLoader extends AbstractIndependentDriverLoader
+        implements DefaultDriverProviderService {
     public DefaultDriversLoader() {
         super("/onos-drivers.xml");
     }