Modify DiscreteResourceCodec interface

This is for ONOS-4281

Change-Id: Idaa4e3666946ebf1a76abfeb54c626dfb50082c4

@@ -18,26 +18,25 @@ package org.onosproject.net.resource;
 import com.google.common.annotations.Beta;
 
 /**
- * Represents the common interface to encode a discrete resource to an integer,
- * and to decode an integer to a discrete resource.
+ * Represents the common interface to encode an object of the specified type to an integer,
+ * and to decode an integer to an object of the specified type.
  * This class is intended to be used only by the ResourceService implementation.
  */
 @Beta
-public interface DiscreteResourceCodec {
+public interface DiscreteResourceCodec<T> {
     /**
-     * Encodes the specified discrete resource to an integer.
+     * Encodes the specified object to an integer.
      *
      * @param resource resource
      * @return encoded integer
      */
-    int encode(DiscreteResource resource);
+    int encode(T resource);
 
     /**
-     * Decodes the specified integer to a discrete resource.
+     * Decodes the specified integer to an object.
      *
-     * @param parent parent of the returned resource
      * @param value encoded integer
      * @return decoded discrete resource
      */
-    DiscreteResource decode(DiscreteResourceId parent, int value);
+    T decode(int value);
 }

@@ -24,6 +24,7 @@ import com.google.common.collect.DiscreteDomain;
 import com.google.common.collect.Range;
 import com.google.common.collect.TreeRangeSet;
 import org.onlab.util.ClosedOpenRange;
+import org.onlab.util.Tools;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -45,6 +46,8 @@ public final class DiscreteResourceSetSerializer extends Serializer<DiscreteReso
     public void write(Kryo kryo, Output output, DiscreteResourceSet object) {
         TreeRangeSet<Integer> rangeSet = TreeRangeSet.create();
         object.values().stream()
+                .map(x -> x.valueAs(Object.class))
+                .flatMap(Tools::stream)
                 .map(x -> object.codec().encode(x))
                 .map(Range::singleton)
                 .map(x -> x.canonical(DiscreteDomain.integers()))
@@ -70,7 +73,8 @@ public final class DiscreteResourceSetSerializer extends Serializer<DiscreteReso
 
         Set<DiscreteResource> resources = ranges.stream()
                 .flatMapToInt(x -> IntStream.range(x.lowerBound(), x.upperBound()))
-                .mapToObj(x -> codec.decode(parent, x))
+                .mapToObj(x -> codec.decode(x))
+                .map(x -> Resources.discrete(parent, x).resource())
                 .collect(Collectors.toSet());
 
         return DiscreteResourceSet.of(resources, codec);

@@ -18,25 +18,19 @@ package org.onosproject.net.resource;
 import com.google.common.annotations.Beta;
 import org.onlab.packet.MplsLabel;
 
-import java.util.Optional;
-
-import static com.google.common.base.Preconditions.checkArgument;
-
 /**
  * Codec for MplsLabel.
  */
 @Beta
-public final class MplsCodec implements DiscreteResourceCodec {
+public final class MplsCodec implements DiscreteResourceCodec<MplsLabel> {
     @Override
-    public int encode(DiscreteResource resource) {
-        Optional<MplsLabel> mpls = resource.valueAs(MplsLabel.class);
-        checkArgument(mpls.isPresent());
-        return mpls.map(MplsLabel::toInt).get();
+    public int encode(MplsLabel resource) {
+        return resource.toInt();
     }
 
     @Override
-    public DiscreteResource decode(DiscreteResourceId parent, int value) {
-        return Resources.discrete(parent, MplsLabel.mplsLabel(value)).resource();
+    public MplsLabel decode(int value) {
+        return MplsLabel.mplsLabel(value);
     }
 
     @Override

@@ -19,16 +19,16 @@ package org.onosproject.net.resource;
  * Represents no-op codec intended to used in an empty discrete resource set only.
  * It's not supposed to be used by other classes.
  */
-public class NoOpCodec implements DiscreteResourceCodec {
+public class NoOpCodec implements DiscreteResourceCodec<Object> {
     public static final DiscreteResourceCodec INSTANCE = new NoOpCodec();
 
     @Override
-    public int encode(DiscreteResource resource) {
+    public int encode(Object resource) {
         return 0;
     }
 
     @Override
-    public DiscreteResource decode(DiscreteResourceId parent, int value) {
+    public Object decode(int value) {
         return Resource.ROOT;
     }
 

@@ -18,25 +18,19 @@ package org.onosproject.net.resource;
 import com.google.common.annotations.Beta;
 import org.onlab.packet.VlanId;
 
-import java.util.Optional;
-
-import static com.google.common.base.Preconditions.checkArgument;
-
 /**
  * Codec for Vlan.
  */
 @Beta
-public final class VlanCodec implements DiscreteResourceCodec {
+public final class VlanCodec implements DiscreteResourceCodec<VlanId> {
     @Override
-    public int encode(DiscreteResource resource) {
-        Optional<VlanId> vlan = resource.valueAs(VlanId.class);
-        checkArgument(vlan.isPresent());
-        return vlan.map(x -> (int) x.toShort()).get();
+    public int encode(VlanId resource) {
+        return resource.toShort();
     }
 
     @Override
-    public DiscreteResource decode(DiscreteResourceId parent, int value) {
-        return Resources.discrete(parent, VlanId.vlanId((short) value)).resource();
+    public VlanId decode(int value) {
+        return VlanId.vlanId((short) value);
     }
 
     @Override