Fix #5103: pass Object size to writeStartObject() for ObjectNode serialization (#5118)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -8,6 +8,8 @@ Project: jackson-databind
 
 #4136: Drop deprecated (in 2.12) `PropertyNamingStrategy` implementations
   from 2.20
+#5103: Use `writeStartObject(Object forValue, int size)` for `ObjectNode`
+  serialization
 
 2.19.0 (24-Apr-2025)
 

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

@@ -233,7 +233,6 @@ protected ArrayNode _withArrayAddTailProperty(JsonPointer tail, boolean preferIn
         return putObject(propName)._withArrayAddTailProperty(tail, preferIndex);
     }
 
-
     /*
     /**********************************************************
     /* Overrides for JsonSerializable.Base
@@ -489,24 +488,25 @@ public List<JsonNode> findParents(String propertyName, List<JsonNode> foundSoFar
      */
     @SuppressWarnings("deprecation")
     @Override
-    public void serialize(JsonGenerator g, SerializerProvider provider)
+    public void serialize(JsonGenerator g, SerializerProvider ctxt)
         throws IOException
     {
-        if (provider != null) {
-            boolean trimEmptyArray = !provider.isEnabled(SerializationFeature.WRITE_EMPTY_JSON_ARRAYS);
-            boolean skipNulls = !provider.isEnabled(JsonNodeFeature.WRITE_NULL_PROPERTIES);
+        if (ctxt != null) {
+            boolean trimEmptyArray = !ctxt.isEnabled(SerializationFeature.WRITE_EMPTY_JSON_ARRAYS);
+            boolean skipNulls = !ctxt.isEnabled(JsonNodeFeature.WRITE_NULL_PROPERTIES);
             if (trimEmptyArray || skipNulls) {
                 g.writeStartObject(this);
-                serializeFilteredContents(g, provider, trimEmptyArray, skipNulls);
+                serializeFilteredContents(g, ctxt, trimEmptyArray, skipNulls);
                 g.writeEndObject();
                 return;
             }
         }
-        g.writeStartObject(this);
-        for (Map.Entry<String, JsonNode> en : _contentsToSerialize(provider).entrySet()) {
-            JsonNode value = en.getValue();
+        Map<String, JsonNode> contents = _contentsToSerialize(ctxt);
+        // 25-Apr-2025, tatu: [databind#5103] Pass size (some formats can optimize)
+        g.writeStartObject(this, contents.size());
+        for (Map.Entry<String, JsonNode> en : contents.entrySet()) {
             g.writeFieldName(en.getKey());
-            value.serialize(g, provider);
+            en.getValue().serialize(g, ctxt);
         }
         g.writeEndObject();
     }