Fix issue FasterXML#731 - returning Object from Converter

Author: Spikhalskiy

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

@@ -12,6 +12,7 @@
 import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
 import com.fasterxml.jackson.databind.ser.*;
 import com.fasterxml.jackson.databind.ser.impl.*;
+import com.fasterxml.jackson.databind.ser.std.DynamicSerializer;
 import com.fasterxml.jackson.databind.ser.std.NullSerializer;
 import com.fasterxml.jackson.databind.type.TypeFactory;
 import com.fasterxml.jackson.databind.util.ClassUtil;
@@ -829,6 +830,16 @@ public JsonSerializer<Object> getUnknownTypeSerializer(Class<?> unknownType) {
     public boolean isUnknownTypeSerializer(JsonSerializer<?> ser) {
         return (ser == _unknownTypeSerializer) || (ser == null);
     }
+
+    /**
+     * Helper method called to see if given serializer is a dynamic serializer, that is, something
+     * for which no regular serializer was found or constructed and it will be a try to find actual serializer in runtime.
+     *
+     * @since 2.5
+     */
+    public boolean isDynamicSerializer(JsonSerializer<?> ser) {
+        return ser instanceof DynamicSerializer;
+    }
 
     /*
     /**********************************************************
@@ -1094,8 +1105,9 @@ protected JsonSerializer<Object> _findExplicitUntypedSerializer(Class<?> runtime
          *    that pushes creation of "unknown type" serializer deeper down
          *    in BeanSerializerFactory; as a result, we need to "undo" creation
          *    here.
+         * 14-Mar-2015 If we have DynamicSerializer here it means that we actually don't have explicit serializer and will try to detect it in runtime
          */
-        if (isUnknownTypeSerializer(ser)) {
+        if (isDynamicSerializer(ser) || isUnknownTypeSerializer(ser)) {
             return null;
         }
         return ser;

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

@@ -13,6 +13,7 @@
 import com.fasterxml.jackson.databind.ser.impl.FilteredBeanPropertyWriter;
 import com.fasterxml.jackson.databind.ser.impl.ObjectIdWriter;
 import com.fasterxml.jackson.databind.ser.impl.PropertyBasedObjectIdGenerator;
+import com.fasterxml.jackson.databind.ser.std.DynamicSerializer;
 import com.fasterxml.jackson.databind.ser.std.MapSerializer;
 import com.fasterxml.jackson.databind.ser.std.StdDelegatingSerializer;
 import com.fasterxml.jackson.databind.type.*;
@@ -339,7 +340,7 @@ protected JsonSerializer<Object> constructBeanSerializer(SerializerProvider prov
         // 13-Oct-2010, tatu: quick sanity check: never try to create bean serializer for plain Object
         // 05-Jul-2012, tatu: ... but we should be able to just return "unknown type" serializer, right?
         if (beanDesc.getBeanClass() == Object.class) {
-            return prov.getUnknownTypeSerializer(Object.class);
+            return new DynamicSerializer(prov.getUnknownTypeSerializer(Object.class));
 //            throw new IllegalArgumentException("Can not create bean serializer for Object.class");
         }
         final SerializationConfig config = prov.getConfig();

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

@@ -0,0 +1,68 @@
+package com.fasterxml.jackson.databind.ser.std;
+
+import java.io.IOException;
+import java.lang.reflect.Type;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.JsonMappingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitorWrapper;
+import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
+
+/**
+ * Use serializer of this class in case of type and serializer for this type can't detect statically
+ * For example, if intermediate {@link com.fasterxml.jackson.databind.util.Converter} return generic Object value,
+ * this serializer can be used to get actual serializer in runtime
+ */
+@SuppressWarnings("serial")
+public class DynamicSerializer
+    extends StdSerializer<Object>
+{
+    private final JsonSerializer<Object> chainedSerializer;
+
+    public DynamicSerializer(JsonSerializer<Object> chainedSerializer) {
+        super(Object.class);
+        this.chainedSerializer = chainedSerializer;
+    }
+    
+    @Override
+    public void serialize(Object value, JsonGenerator jgen, SerializerProvider provider)
+        throws IOException
+    {
+        JsonSerializer<Object> dynamicSerializer = provider.findValueSerializer(value.getClass());
+        if (dynamicSerializer != null && !provider.isDynamicSerializer(dynamicSerializer)) {
+            dynamicSerializer.serialize(value, jgen, provider);
+        } else {
+            chainedSerializer.serialize(value, jgen, provider);
+        }
+    }
+
+    @Override
+    public final void serializeWithType(Object value, JsonGenerator jgen, SerializerProvider provider,
+            TypeSerializer typeSer)
+        throws IOException
+    {
+        JsonSerializer<Object> dynamicSerializer = provider.findValueSerializer(value.getClass());
+        if (dynamicSerializer != null) {
+            dynamicSerializer.serializeWithType(value, jgen, provider, typeSer);
+        }
+
+        chainedSerializer.serializeWithType(value, jgen, provider, typeSer);
+    }
+    
+    @Override
+    public JsonNode getSchema(SerializerProvider provider, Type typeHint) throws JsonMappingException
+    {
+        return null;
+    }
+    
+    @Override
+    public void acceptJsonFormatVisitor(JsonFormatVisitorWrapper visitor, JavaType typeHint)
+        throws JsonMappingException
+    { 
+        visitor.expectAnyFormat(typeHint);
+    }
+}

src/test/java/com/fasterxml/jackson/databind/convert/TestBeanConversions.java

@@ -63,7 +63,15 @@ static class Leaf {
         public Leaf() { }
         public Leaf(int v) { value = v; }
     }
-    
+
+    public static class DummyBean {
+        public final int a, b;
+        public DummyBean(int v1, int v2) {
+            a = v1 * 2;
+            b = v2 * 2;
+        }
+    }
+
     // [Issue#288]
 
     @JsonSerialize(converter = ConvertingBeanConverter.class)
@@ -75,14 +83,6 @@ public ConvertingBean(int v1, int v2) {
        }
     }
 
-    public static class DummyBean {
-       public final int a, b;
-       public DummyBean(int v1, int v2) {
-          a = v1 * 2;
-          b = v2 * 2;
-       }
-    }
-
     static class ConvertingBeanConverter extends StdConverter<ConvertingBean, DummyBean>
     {
        @Override
@@ -91,6 +91,25 @@ public DummyBean convert(ConvertingBean cb) {
        }
     }
 
+    // [Issue#731]
+
+    @JsonSerialize(converter = UntypedConvertingBeanConverter.class)
+    static class ConvertingBeanWithUntypedConverter {
+        public int x, y;
+        public ConvertingBeanWithUntypedConverter(int v1, int v2) {
+            x = v1;
+            y = v2;
+        }
+    }
+
+    static class UntypedConvertingBeanConverter extends StdConverter<ConvertingBeanWithUntypedConverter, Object>
+    {
+        @Override
+        public Object convert(ConvertingBeanWithUntypedConverter cb) {
+            return new DummyBean(cb.x, cb.y);
+        }
+    }
+
     /*
     /**********************************************************
     /* Test methods
@@ -252,5 +271,12 @@ public void testConversionIssue288() throws Exception
         String json = MAPPER.writeValueAsString(new ConvertingBean(1, 2));
         // must be  {"a":2,"b":4}
         assertEquals("{\"a\":2,\"b\":4}", json);
-     }
+    }
+
+    public void testIssue731() throws Exception
+    {
+        String json = MAPPER.writeValueAsString(new ConvertingBeanWithUntypedConverter(1, 2));
+        // must be  {"a":2,"b":4}
+        assertEquals("{\"a\":2,\"b\":4}", json);
+    }
 }

src/test/java/com/fasterxml/jackson/databind/ser/TestSerializerProvider.java

@@ -3,7 +3,6 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 import com.fasterxml.jackson.databind.*;
-import com.fasterxml.jackson.databind.ser.BeanSerializerFactory;
 
 public class TestSerializerProvider
     extends com.fasterxml.jackson.databind.BaseMapTest