Implement #3476

release-notes/VERSION-2.x

@@ -19,6 +19,8 @@ Project: jackson-databind
   JSON `null` values on reading
 #3443: Do not strip generic type from `Class<C>` when resolving `JavaType`
  (contributed by Jan J)
+#3476: Implement `JsonNodeFeature.WRITE_NULL_PROPERTIES` to allow skipping
+  JSON `null` values on writing
 
 2.13.3 (not yet released)
 

src/main/java/com/fasterxml/jackson/databind/node/ObjectNode.java

@@ -8,6 +8,7 @@
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.core.type.WritableTypeId;
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.cfg.JsonNodeFeature;
 import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
 import com.fasterxml.jackson.databind.util.RawValue;
 
@@ -302,59 +303,87 @@ public List<JsonNode> findParents(String propertyName, List<JsonNode> foundSoFar
      * Method that can be called to serialize this node and
      * all of its descendants using specified JSON generator.
      */
+    @SuppressWarnings("deprecation")
     @Override
     public void serialize(JsonGenerator g, SerializerProvider provider)
         throws IOException
     {
-        @SuppressWarnings("deprecation")
-        boolean trimEmptyArray = (provider != null) &&
-                !provider.isEnabled(SerializationFeature.WRITE_EMPTY_JSON_ARRAYS);
+        if (provider != null) {
+            boolean trimEmptyArray = !provider.isEnabled(SerializationFeature.WRITE_EMPTY_JSON_ARRAYS);
+            boolean skipNulls = !provider.isEnabled(JsonNodeFeature.WRITE_NULL_PROPERTIES);
+            if (trimEmptyArray || skipNulls) {
+                g.writeStartObject(this);
+                serializeFilteredContents(g, provider, trimEmptyArray, skipNulls);
+                g.writeEndObject();
+                return;
+            }
+        }
         g.writeStartObject(this);
         for (Map.Entry<String, JsonNode> en : _children.entrySet()) {
-            /* 17-Feb-2009, tatu: Can we trust that all nodes will always
-             *   extend BaseJsonNode? Or if not, at least implement
-             *   JsonSerializable? Let's start with former, change if
-             *   we must.
-             */
-            BaseJsonNode value = (BaseJsonNode) en.getValue();
-
-            // as per [databind#867], see if WRITE_EMPTY_JSON_ARRAYS feature is disabled,
-            // if the feature is disabled, then should not write an empty array
-            // to the output, so continue to the next element in the iteration
-            if (trimEmptyArray && value.isArray() && value.isEmpty(provider)) {
-            	continue;
-            }
+            JsonNode value = en.getValue();
             g.writeFieldName(en.getKey());
             value.serialize(g, provider);
         }
         g.writeEndObject();
     }
 
+    @SuppressWarnings("deprecation")
     @Override
     public void serializeWithType(JsonGenerator g, SerializerProvider provider,
             TypeSerializer typeSer)
         throws IOException
     {
-        @SuppressWarnings("deprecation")
-        boolean trimEmptyArray = (provider != null) &&
-                !provider.isEnabled(SerializationFeature.WRITE_EMPTY_JSON_ARRAYS);
+        boolean trimEmptyArray = false;
+        boolean skipNulls = false;
+        if (provider != null) {
+            trimEmptyArray = !provider.isEnabled(SerializationFeature.WRITE_EMPTY_JSON_ARRAYS);
+            skipNulls = !provider.isEnabled(JsonNodeFeature.WRITE_NULL_PROPERTIES);
+        }
 
         WritableTypeId typeIdDef = typeSer.writeTypePrefix(g,
                 typeSer.typeId(this, JsonToken.START_OBJECT));
+
+        if (trimEmptyArray || skipNulls) {
+            serializeFilteredContents(g, provider, trimEmptyArray, skipNulls);
+        } else {
+            for (Map.Entry<String, JsonNode> en : _children.entrySet()) {
+                JsonNode value = en.getValue();
+                g.writeFieldName(en.getKey());
+                value.serialize(g, provider);
+            }
+        }
+        typeSer.writeTypeSuffix(g, typeIdDef);
+    }
+
+    /**
+     * Helper method shared and called by {@link #serialize} and {@link #serializeWithType}
+     * in cases where actual filtering is needed based on configuration.
+     *
+     * @since 2.14
+     */
+    protected void serializeFilteredContents(final JsonGenerator g, final SerializerProvider provider,
+            final boolean trimEmptyArray, final boolean skipNulls)
+        throws IOException
+    {
         for (Map.Entry<String, JsonNode> en : _children.entrySet()) {
+            // 17-Feb-2009, tatu: Can we trust that all nodes will always
+            //   extend BaseJsonNode? Or if not, at least implement
+            //   JsonSerializable? Let's start with former, change if
+            //   we must.
             BaseJsonNode value = (BaseJsonNode) en.getValue();
 
-            // check if WRITE_EMPTY_JSON_ARRAYS feature is disabled,
+            // as per [databind#867], see if WRITE_EMPTY_JSON_ARRAYS feature is disabled,
             // if the feature is disabled, then should not write an empty array
             // to the output, so continue to the next element in the iteration
             if (trimEmptyArray && value.isArray() && value.isEmpty(provider)) {
+               continue;
+            }
+            if (skipNulls && value.isNull()) {
                 continue;
             }
-
             g.writeFieldName(en.getKey());
             value.serialize(g, provider);
         }
-        typeSer.writeTypeSuffix(g, typeIdDef);
     }
 
     /*

src/test/java/com/fasterxml/jackson/databind/node/NodeFeaturesTest.java

@@ -9,22 +9,34 @@ public class NodeFeaturesTest extends BaseMapTest
 {
     private final ObjectMapper MAPPER = newJsonMapper();
     private final ObjectReader READER = MAPPER.reader();
+    private final ObjectWriter WRITER = MAPPER.writer();
 
     private final ObjectNode DOC_EMPTY = MAPPER.createObjectNode();
     private final ObjectNode DOC_WITH_NULL = MAPPER.createObjectNode();
     {
         DOC_WITH_NULL.putNull("nvl");
     }
+    private final String JSON_EMPTY = ("{}");
     private final String JSON_WITH_NULL = a2q("{'nvl':null}");
 
     public void testDefaultSettings() throws Exception
     {
         assertTrue(READER.isEnabled(JsonNodeFeature.READ_NULL_PROPERTIES));
-
         assertFalse(READER.without(JsonNodeFeature.READ_NULL_PROPERTIES)
                 .isEnabled(JsonNodeFeature.READ_NULL_PROPERTIES));
+
+        assertTrue(READER.isEnabled(JsonNodeFeature.WRITE_NULL_PROPERTIES));
+        assertFalse(READER.without(JsonNodeFeature.WRITE_NULL_PROPERTIES)
+                .isEnabled(JsonNodeFeature.WRITE_NULL_PROPERTIES));
     }
 
+    /*
+    /**********************************************************************
+    /* ObjectNode property handling
+    /**********************************************************************
+     */
+
+    // [databind#3421]
     public void testReadNulls() throws Exception
     {
         // so by default we'll get null included
@@ -47,4 +59,35 @@ public void testReadNulls() throws Exception
         exp.put("c", true);
         assertEquals(exp, r.readTree(a2q("{'a':1,'b':null,'c':true}")));
     }
+
+    // [databind#3476]
+    public void testWriteNulls() throws Exception
+    {
+        // so by default we'll get null written
+        assertEquals(JSON_WITH_NULL, WRITER.writeValueAsString(DOC_WITH_NULL));
+
+        ObjectMapper noNullsMapper = JsonMapper.builder()
+                .disable(JsonNodeFeature.WRITE_NULL_PROPERTIES)
+                .build();
+        ObjectWriter w = noNullsMapper.writer();
+        assertFalse(w.isEnabled(JsonNodeFeature.WRITE_NULL_PROPERTIES));
+        assertEquals(JSON_EMPTY, w.writeValueAsString(DOC_WITH_NULL));
+
+        // but also verify we can "reset" writer's behavior
+        ObjectWriter w2 = w.with(JsonNodeFeature.WRITE_NULL_PROPERTIES);
+        assertEquals(JSON_WITH_NULL, w2.writeValueAsString(DOC_WITH_NULL));
+
+        // and then bit more complex doc
+        ObjectNode doc = noNullsMapper.createObjectNode();
+        doc.put("a", 1);
+        doc.putNull("b");
+        doc.put("c", true);
+        assertEquals(a2q("{'a':1,'c':true}"), w.writeValueAsString(doc));
+    }
+
+    /*
+    /**********************************************************************
+    /* Other features
+    /**********************************************************************
+     */
 }