Fix #1973

release-notes/VERSION

@@ -29,6 +29,7 @@ Versions: 3.x (for earlier see VERSION-2.x)
 #1916: Change `MapperFeature.USE_GETTERS_AS_SETTERS)` default to `false`
 #1917: Remove `canSerialize` and `canDeserialize` methods from `ObjectMapper`
 #1954: Add Builder pattern for creating configured `ObjectMapper` instances
-- Remove `MappingJsonFactory`
 #1955: Change the way `Module`s configure, interact with `ObjectMapper`
-
+#1973: Remove support for "default [Map] key serializer" configuration from
+  `SerializerProvider`
+- Remove `MappingJsonFactory`

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

@@ -82,9 +82,9 @@ public abstract class SerializerProvider
     protected final static JsonSerializer<Object> DEFAULT_UNKNOWN_SERIALIZER = new UnknownSerializer();
 
     /*
-    /**********************************************************
+    /**********************************************************************
     /* Configuration, general
-    /**********************************************************
+    /**********************************************************************
      */
 
     /**
@@ -154,13 +154,6 @@ public abstract class SerializerProvider
      */
     protected JsonSerializer<Object> _unknownTypeSerializer = DEFAULT_UNKNOWN_SERIALIZER;
 
-    /**
-     * Serializer used to output non-null keys of Maps (which will get
-     * output as JSON Objects), if not null; if null, us the standard
-     * default key serializer.
-     */
-    protected JsonSerializer<Object> _defaulKeySerializer;
-
     /**
      * Serializer used to output a null value. Default implementation
      * writes nulls using {@link JsonGenerator#writeNull}.
@@ -252,7 +245,6 @@ protected SerializerProvider(SerializerProvider src,
 
         _serializerCache = src._serializerCache;
         _unknownTypeSerializer = src._unknownTypeSerializer;
-        _defaulKeySerializer = src._defaulKeySerializer;
         _nullValueSerializer = src._nullValueSerializer;
         _nullKeySerializer = src._nullKeySerializer;
 
@@ -285,7 +277,6 @@ protected SerializerProvider(SerializerProvider src)
         _serializerCache = new SerializerCache();
 
         _unknownTypeSerializer = src._unknownTypeSerializer;
-        _defaulKeySerializer = src._defaulKeySerializer;
         _nullValueSerializer = src._nullValueSerializer;
         _nullKeySerializer = src._nullKeySerializer;
 
@@ -386,20 +377,6 @@ public void writeTree(JsonGenerator gen, TreeNode tree) throws IOException
     /**********************************************************************
      */
 
-    /**
-     * Method that can be used to specify serializer that will be
-     * used to write JSON property names matching null keys for Java
-     * Maps (which will throw an exception if try write such property
-     * name)
-     */
-    public void setDefaultKeySerializer(JsonSerializer<Object> ks)
-    {
-        if (ks == null) {
-            throw new IllegalArgumentException("Cannot pass null JsonSerializer");
-        }
-        _defaulKeySerializer = ks;
-    }
-
     /**
      * Method that can be used to specify serializer that will be
      * used to write JSON values matching Java null values
@@ -886,8 +863,9 @@ public TypeSerializer findTypeSerializer(JavaType javaType) throws JsonMappingEx
     public JsonSerializer<Object> findKeySerializer(JavaType keyType, BeanProperty property)
         throws JsonMappingException
     {
-        JsonSerializer<Object> ser = _serializerFactory.createKeySerializer(_config, keyType, _defaulKeySerializer);
-        // 25-Feb-2011, tatu: As per [JACKSON-519], need to ensure contextuality works here, too
+        // 16-Mar-2018, tatu: Used to have "default key serializer" in 2.x; dropped to let/make
+        //    custom code use Module interface or similar to provide key serializers
+        JsonSerializer<Object> ser = _serializerFactory.createKeySerializer(_config, keyType, null);
         return _handleContextualResolvable(ser, property);
     }
 

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

@@ -47,8 +47,6 @@ public abstract class SerializerFactory
       * 
       * @param prov Provider that needs to be used to resolve annotation-provided
       *    serializers (but NOT for others)
-      *    
-      * @since 2.1 (earlier versions had method with different signature)
       */
     public abstract JsonSerializer<Object> createSerializer(SerializerProvider prov,
             JavaType baseType)

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

@@ -78,8 +78,6 @@ public static JsonSerializer<Object> getStdKeySerializer(SerializationConfig con
     /**
      * Method called if no specified key serializer was located; will return a
      * "default" key serializer.
-     *
-     * @since 2.7
      */
     @SuppressWarnings("unchecked")
     public static JsonSerializer<Object> getFallbackKeySerializer(SerializationConfig config,

src/test/java/com/fasterxml/jackson/databind/ser/jdk/MapKeySerializationTest.java

@@ -7,8 +7,9 @@
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonValue;
+
 import com.fasterxml.jackson.core.Base64Variants;
-import com.fasterxml.jackson.core.JsonGenerator;
+
 import com.fasterxml.jackson.databind.*;
 
 @SuppressWarnings("serial")
@@ -37,15 +38,6 @@ public String toString() {
 
     static class WatMap extends HashMap<Wat,Boolean> { }
 
-    static class DefaultKeySerializer extends JsonSerializer<Object>
-    {
-        @Override
-        public void serialize(Object value, JsonGenerator g, SerializerProvider provider) throws IOException
-        {
-            g.writeFieldName("DEFAULT:"+value);
-        }
-    }
-
     /*
     /**********************************************************
     /* Test methods
@@ -73,15 +65,6 @@ public void testClassKey() throws IOException
         assertEquals(aposToQuotes("{'java.lang.String':2}"), json);
     }
 
-    public void testDefaultKeySerializer() throws IOException
-    {
-        ObjectMapper m = new ObjectMapper();
-        m.getSerializerProvider().setDefaultKeySerializer(new DefaultKeySerializer());
-        Map<String,String> map = new HashMap<String,String>();
-        map.put("a", "b");
-        assertEquals("{\"DEFAULT:a\":\"b\"}", m.writeValueAsString(map));
-    }
-
     // [databind#1552]
     public void testMapsWithBinaryKeys() throws Exception
     {