yet more work on merging; avoid unnecessary set

18 files changed, 197 insertions, 36 deletions

diff --git a/src/main/java/com/fasterxml/jackson/databind/JsonDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/JsonDeserializer.java
index 068c83d9c..f2806835a 100644
--- a/src/main/java/com/fasterxml/jackson/databind/JsonDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/JsonDeserializer.java
@@ -331,6 +331,29 @@ public abstract class JsonDeserializer<T>
                 +"': type: value deserializer of type "+getClass().getName()+" does not support them");
     }
 
+    /**
+     * Introspection method that may be called to see whether deserializer supports
+     * update of an existing value (aka "merging") or not. Return value should either
+     * be {@link Boolean#FALSE} if update is not supported at all (immutable values);
+     * {@link Boolean#TRUE} if update should usually work (regular POJOs, for example),
+     * or <code>null</code> if this is either not known, or may sometimes work.
+     *<p>
+     * Information gathered is typically used to either prevent merging update for
+     * property (either by skipping, if based on global defaults; or by exception during
+     * deserialization construction if explicit attempt made) if {@link Boolean#FALSE}
+     * returned, or inclusion if {@link Boolean#TRUE} is specified. If "unknown" case
+     * (<code>null</code> returned) behavior is to exclude property if global defaults
+     * used; or to allow if explicit per-type or property merging is defined.
+     *<p>
+     * Default implementation returns <code>null</code> to allow explicit per-type
+     * or per-property attempts.
+     *
+     * @since 2.9
+     */
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return null;
+    }
+
     /*
     /**********************************************************
     /* Deprecated methods
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/AbstractDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/AbstractDeserializer.java
index d00a9318f..c6cfeb37e 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/AbstractDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/AbstractDeserializer.java
@@ -82,7 +82,17 @@ public class AbstractDeserializer
     
     @Override
     public boolean isCachable() { return true; }
-    
+
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        /* 23-Oct-2016, tatu: Not exactly sure what to do with this; polymorphic
+         *   type handling seems bit risky so for now claim it "may or may not be"
+         *   possible, which does allow explicit per-type/per-property merging attempts,
+         *   but avoids general-configuration merges
+         */
+        return null;
+    }
+
     /**
      * Overridden to return true for those instances that are
      * handling value for which Object Identity handling is enabled
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializerBase.java b/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializerBase.java
index 9df98f52e..cc43b53ed 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializerBase.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializerBase.java
@@ -881,6 +881,14 @@ public abstract class BeanDeserializerBase
     @Override
     public boolean isCachable() { return true; }
 
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        // although with possible caveats, yes, values can be updated
+        // 23-Oct-2016, tatu: Perhaps in future could and should verify from
+        //   bean settings...
+        return Boolean.TRUE;
+    }
+    
     @Override
     public Class<?> handledType() {
         return _beanType.getRawClass();
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/impl/FailingDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/impl/FailingDeserializer.java
index 0db8c4c7c..9df6742bd 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/impl/FailingDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/impl/FailingDeserializer.java
@@ -1,5 +1,7 @@
 package com.fasterxml.jackson.databind.deser.impl;
 
+import java.io.IOException;
+
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.JsonMappingException;
@@ -23,7 +25,7 @@ public class FailingDeserializer extends StdDeserializer<Object>
     }
     
     @Override
-    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws JsonMappingException{
+    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
         ctxt.reportInputMismatch(this, _message);
         return null;
     }
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/impl/MergingSettableBeanProperty.java b/src/main/java/com/fasterxml/jackson/databind/deser/impl/MergingSettableBeanProperty.java
index 37fa2f55e..133f67180 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/impl/MergingSettableBeanProperty.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/impl/MergingSettableBeanProperty.java
@@ -66,13 +66,40 @@ public class MergingSettableBeanProperty
     public void deserializeAndSet(JsonParser p, DeserializationContext ctxt,
             Object instance) throws IOException
     {
-        delegate.set(instance, _deserialize(p, ctxt, instance));
+        Object oldValue = _accessor.getValue(instance);
+        Object newValue;
+        // 20-Oct-2016, tatu: Couple of possibilities of how to proceed; for
+        //    now, default to "normal" handling without merging
+        if (oldValue == null) {
+            newValue = delegate.deserialize(p, ctxt);
+        } else {
+            newValue = delegate.deserializeWith(p, ctxt, oldValue);
+        }
+        if (newValue != oldValue) {
+            delegate.set(instance, newValue);
+        }
     }
 
     @Override
     public Object deserializeSetAndReturn(JsonParser p,
-            DeserializationContext ctxt, Object instance) throws IOException {
-        return delegate.setAndReturn(instance, _deserialize(p, ctxt, instance));
+            DeserializationContext ctxt, Object instance) throws IOException
+    {
+        Object oldValue = _accessor.getValue(instance);
+        Object newValue;
+        // 20-Oct-2016, tatu: Couple of possibilities of how to proceed; for
+        //    now, default to "normal" handling without merging
+        if (oldValue == null) {
+            newValue = delegate.deserialize(p, ctxt);
+        } else {
+            newValue = delegate.deserializeWith(p, ctxt, oldValue);
+        }
+        // 23-Oct-2016, tatu: One possible complication here; should we always
+        //    try calling setter on builder? Presumably should not be required,
+        //    but may need to revise
+        if (newValue != oldValue) {
+            return delegate.setAndReturn(instance, newValue);
+        }
+        return instance;
     }
 
     @Override
@@ -86,19 +113,4 @@ public class MergingSettableBeanProperty
     {
         return delegate.setAndReturn(instance, value);
     }
-
-    protected Object _deserialize(JsonParser p, DeserializationContext ctxt,
-            Object instance) throws IOException
-    {
-        Object value = _accessor.getValue(instance);
-        // 20-Oct-2016, tatu: Couple of possibilities of how to proceed; for
-        //    now, default to "normal" handling without merging
-        if (value == null) {
-            return delegate.deserialize(p, ctxt);
-        }
-        Object result = delegate.deserializeWith(p,  ctxt,  value);
-        // 20-Oct-2016, tatu: Similarly, we may get same object or different one;
-        //   whether to return original or new is an open question.
-        return result;
-    }
 }
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/impl/TypeWrappedDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/impl/TypeWrappedDeserializer.java
index 0f23fd1ac..8d5039de6 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/impl/TypeWrappedDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/impl/TypeWrappedDeserializer.java
@@ -37,6 +37,11 @@ public final class TypeWrappedDeserializer
         return _deserializer.handledType();
     }
 
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return _deserializer.supportsUpdate(config);
+    }
+    
     @Override
     public JsonDeserializer<?> getDelegatee() {
         return _deserializer.getDelegatee();
@@ -58,13 +63,13 @@ public final class TypeWrappedDeserializer
     }
     
     @Override
-    public Object deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException
+    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
     {
-        return _deserializer.deserializeWithType(jp, ctxt, _typeDeserializer);
+        return _deserializer.deserializeWithType(p, ctxt, _typeDeserializer);
     }
 
     @Override
-    public Object deserializeWithType(JsonParser jp, DeserializationContext ctxt,
+    public Object deserializeWithType(JsonParser p, DeserializationContext ctxt,
         TypeDeserializer typeDeserializer) throws IOException
     {
         // should never happen? (if it can, could call on that object)
@@ -72,12 +77,12 @@ public final class TypeWrappedDeserializer
     }
 
     @Override
-    public Object deserialize(JsonParser jp, DeserializationContext ctxt,
+    public Object deserialize(JsonParser p, DeserializationContext ctxt,
             Object intoValue) throws IOException
     {
         /* 01-Mar-2013, tatu: Hmmh. Tough call as to what to do... need
          *   to delegate, but will this work reliably? Let's just hope so:
          */
-        return _deserializer.deserialize(jp,  ctxt, intoValue);
+        return _deserializer.deserialize(p,  ctxt, intoValue);
     }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/AtomicReferenceDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/AtomicReferenceDeserializer.java
index 7fe40402b..b7d00300f 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/AtomicReferenceDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/AtomicReferenceDeserializer.java
@@ -25,7 +25,7 @@ public class AtomicReferenceDeserializer
     {
         super(fullType, inst, typeDeser, deser);
     }
-
+    
     /*
     /**********************************************************
     /* Abstract method implementations
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/ContainerDeserializerBase.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/ContainerDeserializerBase.java
index 6b53a29c0..0860a2662 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/ContainerDeserializerBase.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/ContainerDeserializerBase.java
@@ -3,6 +3,7 @@ package com.fasterxml.jackson.databind.deser.std;
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 
+import com.fasterxml.jackson.databind.DeserializationConfig;
 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.JsonDeserializer;
 import com.fasterxml.jackson.databind.JsonMappingException;
@@ -27,6 +28,13 @@ public abstract class ContainerDeserializerBase<T>
     /**********************************************************
      */
 
+    @Override // since 2.9
+    public final Boolean supportsUpdate(DeserializationConfig config) {
+        // 23-Oct-2016, tatu: Most if not all containers should support merges
+        //    so let's default to that:
+        return Boolean.TRUE;
+    }
+    
     @Override
     public SettableBeanProperty findBackReference(String refName) {
         JsonDeserializer<Object> valueDeser = getContentDeserializer();
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/EnumSetDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/EnumSetDeserializer.java
index 213621098..3f1af30bb 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/EnumSetDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/EnumSetDeserializer.java
@@ -96,7 +96,12 @@ public class EnumSetDeserializer
         }
         return true;
     }
-    
+
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return Boolean.TRUE;
+    }
+
     @Override
     public JsonDeserializer<?> createContextual(DeserializationContext ctxt,
             BeanProperty property) throws JsonMappingException
@@ -118,15 +123,32 @@ public class EnumSetDeserializer
     /**********************************************************
      */
 
-    @SuppressWarnings("unchecked") 
     @Override
     public EnumSet<?> deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
     {
+        EnumSet result = constructSet();
         // Ok: must point to START_ARRAY (or equivalent)
         if (!p.isExpectedStartArrayToken()) {
-            return handleNonArray(p, ctxt);
+            return handleNonArray(p, ctxt, result);
         }
-        EnumSet result = constructSet();
+        return _deserialize(p, ctxt, result);
+    }
+
+    @Override
+    public EnumSet<?> deserialize(JsonParser p, DeserializationContext ctxt,
+            EnumSet<?> result) throws IOException
+    {
+        // Ok: must point to START_ARRAY (or equivalent)
+        if (!p.isExpectedStartArrayToken()) {
+            return handleNonArray(p, ctxt, result);
+        }
+        return _deserialize(p, ctxt, result);
+    }
+    
+    @SuppressWarnings("unchecked") 
+    protected final EnumSet<?> _deserialize(JsonParser p, DeserializationContext ctxt,
+            EnumSet result) throws IOException
+    {
         JsonToken t;
 
         try {
@@ -164,12 +186,12 @@ public class EnumSetDeserializer
     @SuppressWarnings("unchecked") 
     private EnumSet constructSet()
     {
-        // superbly ugly... but apparently necessary
         return EnumSet.noneOf(_enumClass);
     }
 
     @SuppressWarnings("unchecked") 
-    protected EnumSet<?> handleNonArray(JsonParser p, DeserializationContext ctxt)
+    protected EnumSet<?> handleNonArray(JsonParser p, DeserializationContext ctxt,
+            EnumSet result)
         throws IOException
     {
         boolean canWrap = (_unwrapSingle == Boolean.TRUE) ||
@@ -179,8 +201,6 @@ public class EnumSetDeserializer
         if (!canWrap) {
             return (EnumSet<?>) ctxt.handleUnexpectedToken(EnumSet.class, p);
         }
-
-        EnumSet result = constructSet();
         // First: since `null`s not allowed, slightly simpler...
         if (p.hasToken(JsonToken.VALUE_NULL)) {
             return (EnumSet<?>) ctxt.handleUnexpectedToken(_enumClass, p);
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/FactoryBasedEnumDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/FactoryBasedEnumDeserializer.java
index cf4096b66..b840ff0aa 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/FactoryBasedEnumDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/FactoryBasedEnumDeserializer.java
@@ -7,6 +7,7 @@ import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.JsonToken;
 import com.fasterxml.jackson.databind.BeanProperty;
+import com.fasterxml.jackson.databind.DeserializationConfig;
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.JavaType;
@@ -99,6 +100,11 @@ class FactoryBasedEnumDeserializer
         return this;
     }
 
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return Boolean.FALSE;
+    }
+
     @Override
     public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
     {
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/JsonNodeDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/JsonNodeDeserializer.java
index 71e19003c..4a3e60365 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/JsonNodeDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/JsonNodeDeserializer.java
@@ -158,6 +158,14 @@ abstract class BaseNodeDeserializer<T extends JsonNode>
     @Override
     public boolean isCachable() { return true; }
 
+    /* 23-Oct-2016, tatu: Certain subtypes (Array, Object) actually do support
+     *   updates, but default to false; can be improved in future.
+     */
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return Boolean.FALSE;
+    }
+    
     /*
     /**********************************************************
     /* Overridable methods
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/NullifyingDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/NullifyingDeserializer.java
index 04535951d..e2d1b8ad8 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/NullifyingDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/NullifyingDeserializer.java
@@ -26,7 +26,12 @@ public class NullifyingDeserializer
     /* Deserializer API
     /**********************************************************
      */
-    
+
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return Boolean.FALSE;
+    }
+
     @Override
     public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
     {
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/PrimitiveArrayDeserializers.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/PrimitiveArrayDeserializers.java
index 109303e0e..381bdc723 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/PrimitiveArrayDeserializers.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/PrimitiveArrayDeserializers.java
@@ -72,6 +72,12 @@ public abstract class PrimitiveArrayDeserializers<T> extends StdDeserializer<T>
         throw new IllegalStateException();
     }
 
+    // !!! TODO: should support, is doable (logically); but not yet supported so:
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return Boolean.FALSE;
+    }
+    
     /**
      * @since 2.7
      */
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/ReferenceTypeDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/ReferenceTypeDeserializer.java
index 1f56aaf68..f3bc2b419 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/ReferenceTypeDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/ReferenceTypeDeserializer.java
@@ -121,6 +121,16 @@ public abstract class ReferenceTypeDeserializer<T>
     @Override
     public JavaType getValueType() { return _fullType; }
 
+    /**
+     * By default we assume that updateability mostly relies on value
+     * deserializer; if it supports updates, typically that's what
+     * matters. So let's just delegate.
+     */
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return _valueDeserializer.supportsUpdate(config);
+    }
+
     /*
     /**********************************************************
     /* Deserialization
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/StdDelegatingDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/StdDelegatingDeserializer.java
index 4f9cd74bd..6bea8c471 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/StdDelegatingDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/StdDelegatingDeserializer.java
@@ -148,6 +148,11 @@ public class StdDelegatingDeserializer<T>
         return _delegateDeserializer.handledType();
     }
 
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return _delegateDeserializer.supportsUpdate(config);
+    }
+
     /*
     /**********************************************************
     /* Serialization
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/StdScalarDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/StdScalarDeserializer.java
index a88bda3bf..a6d7318a4 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/StdScalarDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/StdScalarDeserializer.java
@@ -3,6 +3,7 @@ package com.fasterxml.jackson.databind.deser.std;
 import java.io.IOException;
 
 import com.fasterxml.jackson.core.*;
+import com.fasterxml.jackson.databind.DeserializationConfig;
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
@@ -34,4 +35,14 @@ public abstract class StdScalarDeserializer<T> extends StdDeserializer<T>
     public T deserialize(JsonParser p, DeserializationContext ctxt, T intoValue) throws IOException {
         return deserialize(p, ctxt);
     }
+
+    /**
+     * By default assumption is that scalar types can not be updated: many are immutable
+     * values (such as primitives and wrappers)
+     */
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        return Boolean.FALSE;
+    }
+
 }
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/StringArrayDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/StringArrayDeserializer.java
index 38f319f0e..ecaa243f6 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/StringArrayDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/StringArrayDeserializer.java
@@ -49,6 +49,13 @@ public final class StringArrayDeserializer
         _unwrapSingle = unwrapSingle;
     }
 
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        // 23-Oct-2016, tatu: In theory could support some specific cases; and there's
+        //   question of logical vs physical update. But for now, claim we can't do it.
+        return Boolean.FALSE;
+    }
+    
     /**
      * Contextualization is needed to see whether we can "inline" deserialization
      * of String values, or if we have to use separate value deserializer.
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/UntypedObjectDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/UntypedObjectDeserializer.java
index cff1cdcae..4dcfc4c53 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/UntypedObjectDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/UntypedObjectDeserializer.java
@@ -5,6 +5,7 @@ import java.util.*;
 
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.databind.BeanProperty;
+import com.fasterxml.jackson.databind.DeserializationConfig;
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.JavaType;
@@ -204,6 +205,13 @@ public class UntypedObjectDeserializer
         return true;
     }
 
+    @Override // since 2.9
+    public Boolean supportsUpdate(DeserializationConfig config) {
+        // 23-Oct-2016, tatu: In theory, some values would be updateable (Maps, Collections),
+        //    but seems very error prone, so for now declare that we do not support it.
+        return Boolean.FALSE;
+    }
+
     @Override
     public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
     {
@@ -475,6 +483,13 @@ public class UntypedObjectDeserializer
 
         public Vanilla() { super(Object.class); }
 
+        @Override // since 2.9
+        public Boolean supportsUpdate(DeserializationConfig config) {
+            // 23-Oct-2016, tatu: In theory, some values would be updateable (Maps, Collections),
+            //    but seems very error prone, so for now declare that we do not support it.
+            return Boolean.FALSE;
+        }
+
         @Override
         public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
         {