Fix #52

Author: cowtowncoder

release-notes/CREDITS

@@ -20,3 +20,6 @@ Alexey Kobyakov (akobiakov@github)
   * Reported #64: `@JsonUnwrapped` annotation is ignored when a field is an Optional
    (2.6.0)
 
+Jose Thomas (josethomas@github)
+  * Contributed #52: Guava collection types do not allow null values
+   (2.6.2)

release-notes/VERSION

@@ -6,6 +6,8 @@ Project: jackson-datatype-guava
 
 2.6.2 (not yet released)
 
+#52: Guava collection types do not allow null values
+ (contributed by Jose T)
 #80: Relax OSGi version constraints for Guava dependency.
  (requested by Benson M)
 #82: Problem with polymorphic value types for `Optional`, with 2.6

src/main/java/com/fasterxml/jackson/datatype/guava/deser/GuavaImmutableMapDeserializer.java

@@ -23,27 +23,30 @@ abstract class GuavaImmutableMapDeserializer<T extends ImmutableMap<Object, Obje
     protected abstract ImmutableMap.Builder<Object, Object> createBuilder();
 
     @Override
-    protected T _deserializeEntries(JsonParser jp, DeserializationContext ctxt) throws IOException,
-            JsonProcessingException {
+    protected T _deserializeEntries(JsonParser p, DeserializationContext ctxt)
+        throws IOException, JsonProcessingException
+    {
         final KeyDeserializer keyDes = _keyDeserializer;
         final JsonDeserializer<?> valueDes = _valueDeserializer;
         final TypeDeserializer typeDeser = _typeDeserializerForValue;
 
         ImmutableMap.Builder<Object, Object> builder = createBuilder();
-        for (; jp.getCurrentToken() == JsonToken.FIELD_NAME; jp.nextToken()) {
+        for (; p.getCurrentToken() == JsonToken.FIELD_NAME; p.nextToken()) {
             // Must point to field name now
-            String fieldName = jp.getCurrentName();
+            String fieldName = p.getCurrentName();
             Object key = (keyDes == null) ? fieldName : keyDes.deserializeKey(fieldName, ctxt);
             // And then the value...
-            JsonToken t = jp.nextToken();
+            JsonToken t = p.nextToken();
             // 28-Nov-2010, tatu: Should probably support "ignorable properties" in future...
             Object value;            
             if (t == JsonToken.VALUE_NULL) {
-                value = null;
-            } else if (typeDeser == null) {
-                value = valueDes.deserialize(jp, ctxt);
+                _handleNull(ctxt, fieldName, _valueDeserializer, builder);
+                continue;
+            }
+            if (typeDeser == null) {
+                value = valueDes.deserialize(p, ctxt);
             } else {
-                value = valueDes.deserializeWithType(jp, ctxt, typeDeser);
+                value = valueDes.deserializeWithType(p, ctxt, typeDeser);
             }
             builder.put(key, value);
         }
@@ -54,4 +57,23 @@ protected T _deserializeEntries(JsonParser jp, DeserializationContext ctxt) thro
         return map;
     }
 
-}
+    /**
+     * Overridable helper method called when a JSON null value is encountered.
+     * Since Guava Maps typically do not allow null values, special handling
+     * is needed; default is to simply ignore and skip such values, but alternative
+     * could be to throw an exception.
+     */
+    protected void _handleNull(DeserializationContext ctxt, String fieldName,
+            JsonDeserializer<?> valueDeser,
+            ImmutableMap.Builder<Object, Object> builder) throws IOException
+    {
+        // 14-Sep-2015, tatu: As per [datatype-guava#52], avoid exception due to null
+        // TODO: allow reporting problem via a feature, in future?
+        
+        // Actually, first, see if there's an alternative to Java null
+        Object nvl = valueDeser.getNullValue(ctxt);
+        if (nvl != null) {
+            builder.put(fieldName, nvl);
+        }
+    }
+}

src/test/java/com/fasterxml/jackson/datatype/guava/TestImmutables.java

@@ -185,6 +185,10 @@ public void testImmutableMap() throws Exception
         map = MAPPER.readValue("{}", type);
         assertNotNull(map);
         assertEquals(0, map.size());
+
+        // and for [datatype-guava#52], verify allowance of JSON nulls
+        map = MAPPER.readValue("{\"12\":true,\"4\":null}", type);
+        assertEquals(1, map.size());
     }
 
     public void testTypedImmutableMap() throws Exception