Allow null values for DocumentTree nodes

Change-Id: I88a12727751c6d82843a7b6a9a2e753da1500c99
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/CatalystSerializers.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/CatalystSerializers.java
index 3252f61..aea7aa7 100644
--- a/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/CatalystSerializers.java
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/CatalystSerializers.java
@@ -21,6 +21,7 @@
 import io.atomix.variables.internal.LongCommands;
 
 import java.util.Arrays;
+import java.util.Optional;
 
 import org.onlab.util.Match;
 import org.onosproject.cluster.Leader;
@@ -110,6 +111,7 @@
         serializer.register(ImmutableList.of().getClass(), factory);
         serializer.register(ImmutableList.of("a").getClass(), factory);
         serializer.register(Arrays.asList().getClass(), factory);
+        serializer.register(Optional.class, factory);
 
         serializer.resolve(new LongCommands.TypeResolver());
         serializer.resolve(new AtomixConsistentMapCommands.TypeResolver());
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTree.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTree.java
index 77f9b98..3875e55 100644
--- a/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTree.java
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTree.java
@@ -27,6 +27,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Properties;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Executor;
@@ -108,7 +109,7 @@
 
     @Override
     public CompletableFuture<Versioned<byte[]>> set(DocumentPath path, byte[] value) {
-        return client.submit(new Update(checkNotNull(path), checkNotNull(value), Match.any(), Match.any()))
+        return client.submit(new Update(checkNotNull(path), Optional.ofNullable(value), Match.any(), Match.any()))
                 .thenCompose(result -> {
                     if (result.status() == INVALID_PATH) {
                         return Tools.exceptionalFuture(new NoSuchDocumentPathException());
@@ -136,7 +137,7 @@
         return createInternal(path, value)
                 .thenCompose(status -> {
                     if (status == ILLEGAL_MODIFICATION) {
-                        return createRecursive(path.parent(), new byte[0])
+                        return createRecursive(path.parent(), null)
                                     .thenCompose(r -> createInternal(path, value).thenApply(v -> true));
                     }
                     return CompletableFuture.completedFuture(status == OK);
@@ -145,13 +146,19 @@
 
     @Override
     public CompletableFuture<Boolean> replace(DocumentPath path, byte[] newValue, long version) {
-        return client.submit(new Update(checkNotNull(path), newValue, Match.any(), Match.ifValue(version)))
+        return client.submit(new Update(checkNotNull(path),
+                                        Optional.ofNullable(newValue),
+                                        Match.any(),
+                                        Match.ifValue(version)))
                 .thenApply(result -> result.updated());
     }
 
     @Override
     public CompletableFuture<Boolean> replace(DocumentPath path, byte[] newValue, byte[] currentValue) {
-        return client.submit(new Update(checkNotNull(path), newValue, Match.ifValue(currentValue), Match.any()))
+        return client.submit(new Update(checkNotNull(path),
+                                        Optional.ofNullable(newValue),
+                                        Match.ifValue(currentValue),
+                                        Match.any()))
                 .thenCompose(result -> {
                     if (result.status() == INVALID_PATH) {
                         return Tools.exceptionalFuture(new NoSuchDocumentPathException());
@@ -168,7 +175,7 @@
         if (path.equals(DocumentPath.from("root"))) {
             return Tools.exceptionalFuture(new IllegalDocumentModificationException());
         }
-        return client.submit(new Update(checkNotNull(path), null, Match.ifNotNull(), Match.any()))
+        return client.submit(new Update(checkNotNull(path), null, Match.any(), Match.ifNotNull()))
                 .thenCompose(result -> {
                     if (result.status() == INVALID_PATH) {
                         return Tools.exceptionalFuture(new NoSuchDocumentPathException());
@@ -204,7 +211,7 @@
     }
 
     private CompletableFuture<DocumentTreeUpdateResult.Status> createInternal(DocumentPath path, byte[] value) {
-        return client.submit(new Update(checkNotNull(path), checkNotNull(value), Match.ifNull(), Match.any()))
+        return client.submit(new Update(checkNotNull(path), Optional.ofNullable(value), Match.any(), Match.ifNull()))
                      .thenApply(result -> result.status());
     }
 
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeCommands.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeCommands.java
index f9f7bb1..9921b88 100644
--- a/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeCommands.java
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeCommands.java
@@ -26,6 +26,7 @@
 import io.atomix.copycat.Query;
 
 import java.util.Map;
+import java.util.Optional;
 
 import org.onlab.util.Match;
 import org.onosproject.store.service.DocumentPath;
@@ -139,7 +140,7 @@
     @SuppressWarnings("serial")
     public static class Update extends DocumentTreeCommand<DocumentTreeUpdateResult<byte[]>> {
 
-        private byte[] value;
+        private Optional<byte[]> value;
         private Match<byte[]> valueMatch;
         private Match<Long> versionMatch;
 
@@ -150,14 +151,14 @@
             this.versionMatch = null;
         }
 
-        public Update(DocumentPath path, byte[] value, Match<byte[]> valueMatch, Match<Long> versionMatch) {
+        public Update(DocumentPath path, Optional<byte[]> value, Match<byte[]> valueMatch, Match<Long> versionMatch) {
             super(path);
             this.value = value;
             this.valueMatch = valueMatch;
             this.versionMatch = versionMatch;
         }
 
-        public byte[] value() {
+        public Optional<byte[]> value() {
             return value;
         }
 
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeState.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeState.java
index 06d33b5..cfaa668 100644
--- a/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeState.java
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/resources/impl/AtomixDocumentTreeState.java
@@ -244,7 +244,7 @@
 
         @Override
         public byte[] value() {
-            return commit.operation().value();
+            return commit.operation().value().orElse(null);
         }
 
         @Override