Prohibit null for resources field in Intent

Change-Id: I128c6e63ccccaf817e83ff1c440a731fb98b42f7

@@ -328,7 +328,7 @@ public class IntentsListCommand extends AbstractShellCommand {
     }
 
     private void printDetails(IntentService service, Intent intent) {
-        if (intent.resources() != null && !intent.resources().isEmpty()) {
+        if (!intent.resources().isEmpty()) {
             print("    resources=%s", intent.resources());
         }
         if (intent instanceof ConnectivityIntent) {
@@ -392,7 +392,7 @@ public class IntentsListCommand extends AbstractShellCommand {
             result.put("state", state.toString());
         }
 
-        if (intent.resources() != null && !intent.resources().isEmpty()) {
+        if (!intent.resources().isEmpty()) {
             ArrayNode rnode = mapper.createArrayNode();
             for (NetworkResource resource : intent.resources()) {
                 rnode.add(resource.toString());

@@ -26,6 +26,7 @@ import org.onosproject.net.flow.TrafficSelector;
 import org.onosproject.net.flow.TrafficTreatment;
 import org.onosproject.net.intent.constraint.LinkTypeConstraint;
 
+import java.util.Collections;
 import java.util.List;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -86,7 +87,7 @@ public final class HostToHostIntent extends ConnectivityIntent {
                             TrafficSelector selector,
                             TrafficTreatment treatment,
                             List<Constraint> constraints) {
-        super(appId, null, selector, treatment, constraints);
+        super(appId, Collections.emptyList(), selector, treatment, constraints);
 
         // TODO: consider whether the case one and two are same is allowed
         this.one = checkNotNull(one);

@@ -60,7 +60,7 @@ public abstract class Intent implements BatchOperationTarget {
         checkState(idGenerator != null, "Id generator is not bound.");
         this.id = IntentId.valueOf(idGenerator.getNewId());
         this.appId = checkNotNull(appId, "Application ID cannot be null");
-        this.resources = resources;
+        this.resources = checkNotNull(resources);
     }
 
     /**

@@ -80,7 +80,7 @@ public final class MultiPointToSinglePointIntent extends ConnectivityIntent {
                                          Set<ConnectPoint> ingressPoints,
                                          ConnectPoint egressPoint,
                                          List<Constraint> constraints) {
-        super(appId, null, selector, treatment, constraints);
+        super(appId, Collections.emptyList(), selector, treatment, constraints);
 
         checkNotNull(ingressPoints);
         checkArgument(!ingressPoints.isEmpty(), "Ingress point set cannot be empty");

@@ -18,6 +18,8 @@ package org.onosproject.net.intent;
 import org.onosproject.core.ApplicationId;
 import org.onosproject.net.ConnectPoint;
 
+import java.util.Collections;
+
 /**
  * An optical layer intent for connectivity from one transponder port to another
  * transponder port. No traffic selector or traffic treatment are needed.
@@ -36,7 +38,7 @@ public class OpticalConnectivityIntent extends Intent {
      */
     public OpticalConnectivityIntent(ApplicationId appId,
                                      ConnectPoint src, ConnectPoint dst) {
-        super(appId, null);
+        super(appId, Collections.emptyList());
         this.src = src;
         this.dst = dst;
     }

@@ -24,6 +24,7 @@ import org.onosproject.net.flow.TrafficSelector;
 import org.onosproject.net.flow.TrafficTreatment;
 import org.onosproject.net.intent.constraint.LinkTypeConstraint;
 
+import java.util.Collections;
 import java.util.List;
 
 import static com.google.common.base.Preconditions.checkArgument;
@@ -73,7 +74,7 @@ public class PointToPointIntent extends ConnectivityIntent {
                               ConnectPoint ingressPoint,
                               ConnectPoint egressPoint,
                               List<Constraint> constraints) {
-        super(appId, null, selector, treatment, constraints);
+        super(appId, Collections.emptyList(), selector, treatment, constraints);
 
         checkNotNull(ingressPoint);
         checkNotNull(egressPoint);

@@ -75,7 +75,7 @@ public class SinglePointToMultiPointIntent extends ConnectivityIntent {
             TrafficSelector selector, TrafficTreatment treatment,
             ConnectPoint ingressPoint, Set<ConnectPoint> egressPoints,
             List<Constraint> constraints) {
-        super(appId, null, selector, treatment, constraints);
+        super(appId, Collections.emptyList(), selector, treatment, constraints);
         checkNotNull(egressPoints);
         checkNotNull(ingressPoint);
         checkArgument(!egressPoints.isEmpty(), "Egress point set cannot be empty");

@@ -17,6 +17,8 @@ package org.onosproject.net.intent;
 
 import org.onosproject.TestApplicationId;
 
+import java.util.Collections;
+
 /**
  * An installable intent used in the unit test.
  */
@@ -30,7 +32,7 @@ public class TestInstallableIntent extends Intent {
      * @param value intent ID
      */
     public TestInstallableIntent(int value) { // FIXME
-        super(new TestApplicationId("foo"), null);
+        super(new TestApplicationId("foo"), Collections.emptyList());
         this.value = value;
     }
 

@@ -17,6 +17,8 @@ package org.onosproject.net.intent;
 
 import org.onosproject.TestApplicationId;
 
+import java.util.Collections;
+
 /**
  * An intent used in the unit test.
  */
@@ -30,7 +32,7 @@ public class TestIntent extends Intent {
      * @param value intent ID
      */
     public TestIntent(int value) { // FIXME
-        super(new TestApplicationId("foo"), null);
+        super(new TestApplicationId("foo"), Collections.emptyList());
         this.value = value;
     }
 

@@ -16,6 +16,7 @@
 package org.onosproject.net.intent.impl;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -154,7 +155,7 @@ public class IntentManagerTest {
         private final Long number;
         // Nothing new here
         public MockIntent(Long number) {
-            super(APPID, null);
+            super(APPID, Collections.emptyList());
             this.number = number;
         }
 
@@ -507,7 +508,7 @@ public class IntentManagerTest {
     public void intentWithoutCompiler() {
         class IntentNoCompiler extends Intent {
             IntentNoCompiler() {
-                super(APPID, null);
+                super(APPID, Collections.emptyList());
             }
         }
 

@@ -41,10 +41,8 @@ public class IntentCodec extends JsonCodec<Intent> {
 
         final ArrayNode jsonResources = result.putArray("resources");
 
-        if (intent.resources() != null) {
-            for (final NetworkResource resource : intent.resources()) {
-                jsonResources.add(resource.toString());
-            }
+        for (final NetworkResource resource : intent.resources()) {
+            jsonResources.add(resource.toString());
         }
         return result;
     }

@@ -16,6 +16,7 @@
 package org.onosproject.rest;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.concurrent.atomic.AtomicLong;
 
@@ -300,7 +301,7 @@ public class IntentsResourceTest extends JerseyTest {
     public void testIntentsArray() {
         replay(mockIntentService);
 
-        final Intent intent1 = new MockIntent(null);
+        final Intent intent1 = new MockIntent(Collections.emptyList());
         final HashSet<NetworkResource> resources = new HashSet<>();
         resources.add(new MockResource(1));
         resources.add(new MockResource(2));