Fixed #1284

Author: cowtowncoder

release-notes/VERSION

@@ -16,6 +16,7 @@ Project: jackson-databind
   using `JsonInclude.Include.CUSTOM`
 #1035: `@JsonAnySetter` assumes key of `String`, does not consider declared type.
  (reported by Michael F)
+#1284: Make `StdKeySerializers` use new `JsonGenerator.writeFieldId()` for `int`/`long` keys
 #1320: Add `ObjectNode.put(String, BigInteger)`
  (proposed by Jan L)
 #1341: `DeserializationFeature.FAIL_ON_MISSING_EXTERNAL_TYPE_ID_PROPERTY`

src/main/java/com/fasterxml/jackson/databind/ser/std/StdKeySerializers.java

@@ -40,6 +40,12 @@ public static JsonSerializer<Object> getStdKeySerializer(SerializationConfig con
         if (rawKeyType == String.class) {
             return DEFAULT_STRING_SERIALIZER;
         }
+        if ((rawKeyType == Integer.class) || (rawKeyType == Integer.TYPE)) {
+            return new Default(Default.TYPE_INTEGER, rawKeyType);
+        }
+        if ((rawKeyType == Long.class) || (rawKeyType == Long.TYPE)) {
+            return new Default(Default.TYPE_LONG, rawKeyType);
+        }
         if (rawKeyType.isPrimitive() || Number.class.isAssignableFrom(rawKeyType)) {
             // 28-Jun-2016, tatu: Used to just return DEFAULT_KEY_SERIALIZER, but makes
             //   more sense to use simpler one directly
@@ -121,7 +127,9 @@ public static class Default extends StdSerializer<Object> {
         final static int TYPE_CALENDAR = 2;
         final static int TYPE_CLASS = 3;
         final static int TYPE_ENUM = 4;
-        final static int TYPE_TO_STRING = 5;
+        final static int TYPE_INTEGER = 5; // since 2.9
+        final static int TYPE_LONG = 6; // since 2.9
+        final static int TYPE_TO_STRING = 7;
 
         protected final int _typeId;
 
@@ -149,6 +157,10 @@ public void serialize(Object value, JsonGenerator g, SerializerProvider provider
                     g.writeFieldName(str);
                 }
                 break;
+            case TYPE_INTEGER:
+            case TYPE_LONG:
+                g.writeFieldId(((Number) value).longValue());
+                break;
             case TYPE_TO_STRING:
             default:
                 g.writeFieldName(value.toString());