Explicitly disallow null values in the map

Change-Id: I3b8d287a534e85d9454ca261a8eb666c477c43c1

@@ -21,19 +21,22 @@ import java.util.Set;
 
 /**
  * A distributed, eventually consistent map.
- *
+ * <p>
  * This map does not offer read after writes consistency. Operations are
  * serialized via the timestamps issued by the clock service. If two updates
  * are in conflict, the update with the more recent timestamp will endure.
- *
+ * </p><p>
  * The interface is mostly similar to {@link java.util.Map} with some minor
  * semantic changes and the addition of a listener framework (because the map
  * can be mutated by clients on other instances, not only through the local Java
  * API).
- *
+ * </p><p>
  * Clients are expected to register an
  * {@link org.onosproject.store.impl.EventuallyConsistentMapListener} if they
  * are interested in receiving notifications of update to the map.
+ * </p><p>
+ * Null values are not allowed in this map.
+ * </p>
  */
 public interface EventuallyConsistentMap<K, V> {
 
@@ -84,6 +87,8 @@ public interface EventuallyConsistentMap<K, V> {
      * Clients are expected to register an
      * {@link org.onosproject.store.impl.EventuallyConsistentMapListener} if
      * they are interested in receiving notification of updates to the map.
+     * </p><p>
+     * Null values are not allowed in the map.
      * </p>
      *
      * @param key the key to add a mapping for in this map

@@ -85,6 +85,9 @@ public class EventuallyConsistentMapImpl<K, V>
     private volatile boolean destroyed = false;
     private static final String ERROR_DESTROYED = " map is already destroyed";
 
+    private static final String ERROR_NULL_KEY = "Key cannot be null";
+    private static final String ERROR_NULL_VALUE = "Null values are not allowed";
+
     // TODO: Make these anti-entropy params configurable
     private long initialDelaySec = 5;
     private long periodSec = 5;
@@ -193,12 +196,14 @@ public class EventuallyConsistentMapImpl<K, V>
     @Override
     public boolean containsKey(K key) {
         checkState(!destroyed, mapName + ERROR_DESTROYED);
+        checkNotNull(key, ERROR_NULL_KEY);
         return items.containsKey(key);
     }
 
     @Override
     public boolean containsValue(V value) {
         checkState(!destroyed, mapName + ERROR_DESTROYED);
+        checkNotNull(value, ERROR_NULL_VALUE);
 
         return items.values().stream()
                 .anyMatch(timestamped -> timestamped.value().equals(value));
@@ -207,6 +212,7 @@ public class EventuallyConsistentMapImpl<K, V>
     @Override
     public V get(K key) {
         checkState(!destroyed, mapName + ERROR_DESTROYED);
+        checkNotNull(key, ERROR_NULL_KEY);
 
         Timestamped<V> value = items.get(key);
         if (value != null) {
@@ -218,6 +224,8 @@ public class EventuallyConsistentMapImpl<K, V>
     @Override
     public void put(K key, V value) {
         checkState(!destroyed, mapName + ERROR_DESTROYED);
+        checkNotNull(key, ERROR_NULL_KEY);
+        checkNotNull(value, ERROR_NULL_VALUE);
 
         Timestamp timestamp = clockService.getTimestamp(key);
         if (putInternal(key, value, timestamp)) {
@@ -250,6 +258,7 @@ public class EventuallyConsistentMapImpl<K, V>
     @Override
     public void remove(K key) {
         checkState(!destroyed, mapName + ERROR_DESTROYED);
+        checkNotNull(key, ERROR_NULL_KEY);
 
         Timestamp timestamp = clockService.getTimestamp(key);
         if (removeInternal(key, timestamp)) {
@@ -282,6 +291,10 @@ public class EventuallyConsistentMapImpl<K, V>
         for (Map.Entry<? extends K, ? extends V> entry : m.entrySet()) {
             K key = entry.getKey();
             V value = entry.getValue();
+
+            checkNotNull(key, ERROR_NULL_KEY);
+            checkNotNull(value, ERROR_NULL_VALUE);
+
             Timestamp timestamp = clockService.getTimestamp(entry.getKey());
 
             if (putInternal(key, value, timestamp)) {