Add support "skip nulls" for content values.

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/databind/deser/NullValueProvider.java

@@ -15,12 +15,6 @@
  */
 public interface NullValueProvider
 {
-    /**
-     * Marker object used in some context to mark return value that is to indicate
-     * that `null` should be skipped (instead of being replaced).
-     */
-    public final static Object SKIP_MARKER = new Object();
-    
     /**
      * Method called to possibly convert incoming `null` token (read via
      * underlying streaming input source) into other value of type accessor

src/main/java/com/fasterxml/jackson/databind/deser/impl/NullsConstantProvider.java

@@ -14,7 +14,7 @@ public class NullsConstantProvider
 {
     private static final long serialVersionUID = 1L;
 
-    private final static NullsConstantProvider SKIPPER = new NullsConstantProvider(NullValueProvider.SKIP_MARKER);
+    private final static NullsConstantProvider SKIPPER = new NullsConstantProvider(null);
 
     private final static NullsConstantProvider NULLER = new NullsConstantProvider(null);
 
@@ -29,9 +29,10 @@ protected NullsConstantProvider(Object nvl) {
     }
 
     /**
-     * Static accessor for a stateless instance that always returns
-     * {@link NullValueProvider#SKIP_MARKER} marker instance, used to indicate
-     * that null value is to be skipped instead of replacing it.
+     * Static accessor for a stateless instance used as marker, to indicate
+     * that all input `null` values should be skipped (ignored), so that
+     * no corresponding property value is set (with POJOs), and no content
+     * values (array/Collection elements, Map entries) are added.
      */
     public static NullsConstantProvider skipper() {
         return SKIPPER;
@@ -48,6 +49,24 @@ public static NullsConstantProvider forValue(Object nvl) {
         return new NullsConstantProvider(nvl);
     }
 
+    /**
+     * Utility method that can be used to check if given null value provider
+     * is "skipper", marker provider that means that all input `null`s should
+     * be skipped (ignored), instead of converted
+     */
+    public static boolean isSkipper(NullValueProvider p) {
+        return (p == SKIPPER);
+    }
+
+    /**
+     * Utility method that can be used to check if given null value provider
+     * is "nuller", no-operation provider that will always simply return
+     * Java `null` for any and all input `null`s.
+     */
+    public static boolean isNuller(NullValueProvider p) {
+        return (p == NULLER);
+    }
+    
     @Override
     public AccessPattern getNullAccessPattern() {
         return _access;

src/main/java/com/fasterxml/jackson/databind/deser/std/CollectionDeserializer.java

@@ -188,14 +188,15 @@ public CollectionDeserializer createContextual(DeserializationContext ctxt,
         if (valueTypeDeser != null) {
             valueTypeDeser = valueTypeDeser.forProperty(property);
         }
+        NullValueProvider nuller = findContentNullProvider(ctxt, property, valueDeser);
         if ( (unwrapSingle != _unwrapSingle)
+                || (nuller != _nullProvider)
                 || (delegateDeser != _delegateDeserializer)
                 || (valueDeser != _valueDeserializer)
                 || (valueTypeDeser != _valueTypeDeserializer)
         ) {
             return withResolved(delegateDeser, valueDeser, valueTypeDeser,
-                    findContentNullProvider(ctxt, property, valueDeser),
-                    unwrapSingle);
+                    nuller, unwrapSingle);
         }
         return this;
     }
@@ -276,6 +277,9 @@ public Collection<Object> deserialize(JsonParser p, DeserializationContext ctxt,
             try {
                 Object value;
                 if (t == JsonToken.VALUE_NULL) {
+                    if (_skipNullValues) {
+                        continue;
+                    }
                     value = _nullProvider.getNullValue(ctxt);
                 } else if (typeDeser == null) {
                     value = valueDes.deserialize(p, ctxt);
@@ -339,6 +343,10 @@ protected final Collection<Object> handleNonArray(JsonParser p, DeserializationC
 
         try {
             if (t == JsonToken.VALUE_NULL) {
+                // 03-Feb-2017, tatu: Hmmh. I wonder... let's try skipping here, too
+                if (_skipNullValues) {
+                    return result;
+                }
                 value = _nullProvider.getNullValue(ctxt);
             } else if (typeDeser == null) {
                 value = valueDes.deserialize(p, ctxt);

src/main/java/com/fasterxml/jackson/databind/deser/std/ContainerDeserializerBase.java

@@ -7,6 +7,7 @@
 import com.fasterxml.jackson.databind.deser.NullValueProvider;
 import com.fasterxml.jackson.databind.deser.SettableBeanProperty;
 import com.fasterxml.jackson.databind.deser.ValueInstantiator;
+import com.fasterxml.jackson.databind.deser.impl.NullsConstantProvider;
 import com.fasterxml.jackson.databind.type.TypeFactory;
 import com.fasterxml.jackson.databind.util.AccessPattern;
 import com.fasterxml.jackson.databind.util.ClassUtil;
@@ -37,13 +38,22 @@ public abstract class ContainerDeserializerBase<T>
      * @since 2.9 (demoted from sub-classes where added in 2.7)
      */
     protected final Boolean _unwrapSingle;
-    
+
+    /**
+     * Marker flag set if the <code>_nullProvider</code> indicates that all null
+     * content values should be skipped (instead of being possibly converted).
+     *
+     * @since 2.9
+     */
+    protected final boolean _skipNullValues;
+
     protected ContainerDeserializerBase(JavaType selfType,
             NullValueProvider nuller, Boolean unwrapSingle) {
         super(selfType);
         _containerType = selfType;
         _unwrapSingle = unwrapSingle;
         _nullProvider = nuller;
+        _skipNullValues = NullsConstantProvider.isSkipper(nuller);
     }
 
     protected ContainerDeserializerBase(JavaType selfType) {
@@ -66,6 +76,7 @@ protected ContainerDeserializerBase(ContainerDeserializerBase<?> base,
         _containerType = base._containerType;
         _nullProvider = nuller;
         _unwrapSingle = unwrapSingle;
+        _skipNullValues = NullsConstantProvider.isSkipper(nuller);
     }
 
     /*

src/main/java/com/fasterxml/jackson/databind/deser/std/EnumMapDeserializer.java

@@ -167,13 +167,15 @@ public EnumMap<?,?> deserialize(JsonParser p, DeserializationContext ctxt)
             }
             // And then the value...
             JsonToken t = p.nextToken();
-            /* note: MUST check for nulls separately: deserializers will
-             * not handle them (and maybe fail or return bogus data)
-             */
+            // note: MUST check for nulls separately: deserializers will
+            // not handle them (and maybe fail or return bogus data)
             Object value;
 
             try {
                 if (t == JsonToken.VALUE_NULL) {
+                    if (_skipNullValues) {
+                        continue;
+                    }
                     value = _nullProvider.getNullValue(ctxt);
                 } else if (typeDeser == null) {
                     value =  valueDes.deserialize(p, ctxt);
@@ -190,7 +192,7 @@ public EnumMap<?,?> deserialize(JsonParser p, DeserializationContext ctxt)
 
     @Override
     public Object deserializeWithType(JsonParser jp, DeserializationContext ctxt, TypeDeserializer typeDeserializer)
-        throws IOException, JsonProcessingException
+        throws IOException
     {
         // In future could check current token... for now this should be enough:
         return typeDeserializer.deserializeTypedFromObject(jp, ctxt);

src/main/java/com/fasterxml/jackson/databind/deser/std/MapDeserializer.java

@@ -66,8 +66,6 @@ public class MapDeserializer
 
     protected final ValueInstantiator _valueInstantiator;
 
-    protected final boolean _hasDefaultCreator;
-
     /**
      * Deserializer that is used iff delegate-based creator is
      * to be used for deserializing from JSON Object.
@@ -82,6 +80,8 @@ public class MapDeserializer
      */
     protected PropertyBasedCreator _propertyBasedCreator;    
 
+    protected final boolean _hasDefaultCreator;
+    
     // // Any properties to ignore if seen?
 
     protected Set<String> _ignorableProperties;
@@ -458,6 +458,9 @@ protected final void _readAndBind(JsonParser p, DeserializationContext ctxt,
                 // Note: must handle null explicitly here; value deserializers won't
                 Object value;
                 if (t == JsonToken.VALUE_NULL) {
+                    if (_skipNullValues) {
+                        continue;
+                    }
                     value = _nullProvider.getNullValue(ctxt);
                 } else if (typeDeser == null) {
                     value = valueDes.deserialize(p, ctxt);
@@ -517,6 +520,9 @@ protected final void _readAndBindStringKeyMap(JsonParser p, DeserializationConte
                 // Note: must handle null explicitly here; value deserializers won't
                 Object value;
                 if (t == JsonToken.VALUE_NULL) {
+                    if (_skipNullValues) {
+                        continue;
+                    }
                     value = _nullProvider.getNullValue(ctxt);
                 } else if (typeDeser == null) {
                     value = valueDes.deserialize(p, ctxt);
@@ -585,6 +591,9 @@ public Map<Object,Object> _deserializeUsingCreator(JsonParser p, Deserialization
 
             try {
                 if (t == JsonToken.VALUE_NULL) {
+                    if (_skipNullValues) {
+                        continue;
+                    }
                     value = _nullProvider.getNullValue(ctxt);
                 } else if (typeDeser == null) {
                     value = valueDes.deserialize(p, ctxt);

src/main/java/com/fasterxml/jackson/databind/deser/std/ObjectArrayDeserializer.java

@@ -187,6 +187,9 @@ public Object[] deserialize(JsonParser p, DeserializationContext ctxt)
                 Object value;
 
                 if (t == JsonToken.VALUE_NULL) {
+                    if (_skipNullValues) {
+                        continue;
+                    }
                     value = _nullProvider.getNullValue(ctxt);
                 } else if (typeDeser == null) {
                     value = _elementDeserializer.deserialize(p, ctxt);
@@ -219,9 +222,8 @@ public Object[] deserializeWithType(JsonParser p, DeserializationContext ctxt,
             TypeDeserializer typeDeserializer)
         throws IOException
     {
-        /* Should there be separate handling for base64 stuff?
-         * for now this should be enough:
-         */
+        // Should there be separate handling for base64 stuff?
+        // for now this should be enough:
         return (Object[]) typeDeserializer.deserializeTypedFromArray(p, ctxt);
     }
 
@@ -252,6 +254,9 @@ public Object[] deserialize(JsonParser p, DeserializationContext ctxt,
                 Object value;
 
                 if (t == JsonToken.VALUE_NULL) {
+                    if (_skipNullValues) {
+                        continue;
+                    }
                     value = _nullProvider.getNullValue(ctxt);
                 } else if (typeDeser == null) {
                     value = _elementDeserializer.deserialize(p, ctxt);
@@ -328,6 +333,10 @@ protected Object[] handleNonArray(JsonParser p, DeserializationContext ctxt)
         Object value;
 
         if (t == JsonToken.VALUE_NULL) {
+            // 03-Feb-2017, tatu: Should this be skipped or not?
+            if (_skipNullValues) {
+                return NO_OBJECTS;
+            }
             value = _nullProvider.getNullValue(ctxt);
         } else if (_elementTypeDeserializer == null) {
             value = _elementDeserializer.deserialize(p, ctxt);