Fix #827 with minor modifications

Author: cowtowncoder

release-notes/VERSION

@@ -71,6 +71,8 @@ Project: jackson-databind
   `java.util.Calendar` serialization
 #826: Replaced synchronized HashMap with ConcurrentHashMap in TypeDeserializerBase._findDeserializer
  (contributed by Lars P)
+#827: Fix for polymorphic custom map key serializer
+ (reported by mjr6140@gitgub)
 - Remove old cglib compatibility tests; cause problems in Eclipse
 
 2.5.4 (09-Jun-2015)

src/main/java/com/fasterxml/jackson/databind/ObjectWriter.java

@@ -875,11 +875,12 @@ public void writeValue(JsonGenerator gen, Object value)
                 && (value instanceof Closeable)) {
             _writeCloseableValue(gen, value, _config);
         } else {
-            if (_prefetch.valueSerializer != null) {
-                _serializerProvider(_config).serializeValue(gen, value, _prefetch.rootType,
-                        _prefetch.valueSerializer);
+            JsonSerializer<Object> ser = _prefetch.valueSerializer;
+            if (ser != null) {
+                _serializerProvider(_config).serializeValue(gen, value, _prefetch.rootType, ser);
             } else if (_prefetch.typeSerializer != null) {
-                _serializerProvider(_config).serializePolymorphic(gen, value, _prefetch.typeSerializer);
+                _serializerProvider(_config).serializePolymorphic(gen, value,
+                        _prefetch.rootType, _prefetch.typeSerializer);
             } else {
                 _serializerProvider(_config).serializeValue(gen, value);
             }
@@ -888,7 +889,7 @@ public void writeValue(JsonGenerator gen, Object value)
             }
         }
     }
-    
+
     /*
     /**********************************************************
     /* Serialization methods, others
@@ -1086,7 +1087,8 @@ protected final void _configAndWriteValue(JsonGenerator gen, Object value) throw
                 _serializerProvider(_config).serializeValue(gen, value, _prefetch.rootType,
                         _prefetch.valueSerializer);
             } else if (_prefetch.typeSerializer != null) {
-                _serializerProvider(_config).serializePolymorphic(gen, value, _prefetch.typeSerializer);
+                _serializerProvider(_config).serializePolymorphic(gen, value,
+                        _prefetch.rootType, _prefetch.typeSerializer);
             } else {
                 _serializerProvider(_config).serializeValue(gen, value);
             }
@@ -1121,7 +1123,8 @@ private final void _writeCloseable(JsonGenerator gen, Object value, Serializatio
                 _serializerProvider(cfg).serializeValue(gen, value, _prefetch.rootType,
                         _prefetch.valueSerializer);
             } else if (_prefetch.typeSerializer != null) {
-                _serializerProvider(cfg).serializePolymorphic(gen, value, _prefetch.typeSerializer);
+                _serializerProvider(cfg).serializePolymorphic(gen, value,
+                        _prefetch.rootType, _prefetch.typeSerializer);
             } else {
                 _serializerProvider(cfg).serializeValue(gen, value);
             }
@@ -1165,7 +1168,8 @@ private final void _writeCloseableValue(JsonGenerator gen, Object value, Seriali
                 _serializerProvider(cfg).serializeValue(gen, value, _prefetch.rootType,
                         _prefetch.valueSerializer);
             } else if (_prefetch.typeSerializer != null) {
-                _serializerProvider(cfg).serializePolymorphic(gen, value, _prefetch.typeSerializer);
+                _serializerProvider(cfg).serializePolymorphic(gen, value,
+                        _prefetch.rootType, _prefetch.typeSerializer);
             } else {
                 _serializerProvider(cfg).serializeValue(gen, value);
             }

src/main/java/com/fasterxml/jackson/databind/ser/DefaultSerializerProvider.java

@@ -268,25 +268,39 @@ public void serializeValue(JsonGenerator gen, Object value, JavaType rootType, J
      * Alternate serialization call used for polymorphic types, when {@link TypeSerializer}
      * is already known, but not actual value serializer.
      *
-     * @since 2.5
+     * @since 2.6
      */
-    public void serializePolymorphic(JsonGenerator gen, Object value, TypeSerializer typeSer)
-            throws IOException
+    public void serializePolymorphic(JsonGenerator gen, Object value,
+            JavaType rootType, TypeSerializer typeSer)
+        throws IOException
     {
         if (value == null) {
             _serializeNull(gen);
             return;
         }
-        final Class<?> type = value.getClass();
-        JsonSerializer<Object> ser = findValueSerializer(type, null);
+        // Let's ensure types are compatible at this point
+        if ((rootType != null) && !rootType.getRawClass().isAssignableFrom(value.getClass())) {
+            _reportIncompatibleRootType(value, rootType);
+        }
+        JsonSerializer<Object> ser;
+        /* 12-Jun-2015, tatu: nominal root type is necessary for Maps at least;
+         *   possibly collections, but can cause problems for other polymorphic
+         *   types. We really need to distinguish between serialization type,
+         *   base type; but right we don't. Hence this check
+         */
+        if ((rootType != null) && rootType.isContainerType()) {
+            ser = findValueSerializer(rootType, null);
+        } else {
+            ser = findValueSerializer(value.getClass(), null);
+        }
 
         final boolean wrap;
         PropertyName rootName = _config.getFullRootName();
         if (rootName == null) {
             wrap = _config.isEnabled(SerializationFeature.WRAP_ROOT_VALUE);
             if (wrap) {
                 gen.writeStartObject();
-                PropertyName pname = _config.findRootName(type);
+                PropertyName pname = _config.findRootName(value.getClass());
                 gen.writeFieldName(pname.simpleAsEncoded(_config));
             }
         } else if (rootName.isEmpty()) {
@@ -311,7 +325,18 @@ public void serializePolymorphic(JsonGenerator gen, Object value, TypeSerializer
             throw new JsonMappingException(msg, e);
         }
     }
-    
+
+    /**
+     * @deprecated since 2.6; remove from 2.7 or later
+     */
+    @Deprecated
+    public void serializePolymorphic(JsonGenerator gen, Object value, TypeSerializer typeSer)
+            throws IOException
+    {
+        JavaType t = (value == null) ? null : _config.constructType(value.getClass());
+        serializePolymorphic(gen, value, t, typeSer);
+    }
+
     /**
      * Helper method called when root value to serialize is null
      * 

src/test/java/com/fasterxml/jackson/databind/seq/ObjectWriterTest.java

@@ -93,7 +93,7 @@ public void testObjectWriterWithNode() throws Exception
         assertEquals("{\"a\":5}", json);
     }
 
-    public void testPolymorpicWithTyping() throws Exception
+    public void testPolymorphicWithTyping() throws Exception
     {
         ObjectWriter writer = MAPPER.writerFor(PolyBase.class);
         String json;

src/test/java/com/fasterxml/jackson/failing/PolyMapWriter827Test.java renamed to src/test/java/com/fasterxml/jackson/databind/seq/PolyMapWriter827Test.java

@@ -1,4 +1,4 @@
-package com.fasterxml.jackson.failing;
+package com.fasterxml.jackson.databind.seq;
 
 import java.io.IOException;
 import java.util.HashMap;