Further improvements related to #1711 to both catch problem AND to allow handling via DeserializationProblemHandler

Author: cowtowncoder

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

@@ -944,7 +944,7 @@ public Object handleWeirdNumberValue(Class<?> targetClass, Number value,
                 if ((key == null) || targetClass.isInstance(key)) {
                     return key;
                 }
-                throw weirdNumberException(value, targetClass, String.format(
+                throw weirdNumberException(value, targetClass, _format(
                         "DeserializationProblemHandler.handleWeirdNumberValue() for type %s returned value of type %s",
                         targetClass, key.getClass()));
             }
@@ -953,6 +953,28 @@ public Object handleWeirdNumberValue(Class<?> targetClass, Number value,
         throw weirdNumberException(value, targetClass, msg);
     }
 
+    public Object handleWeirdNativeValue(JavaType targetType, Object badValue,
+            JsonParser p)
+        throws IOException
+    {
+        LinkedNode<DeserializationProblemHandler> h = _config.getProblemHandlers();
+        final Class<?> raw = targetType.getRawClass();
+        for (; h != null; h = h.next()) {
+            // Can bail out if it's handled
+            Object goodValue = h.value().handleWeirdNativeValue(this, targetType, badValue, p);
+            if (goodValue != DeserializationProblemHandler.NOT_HANDLED) {
+                // Sanity check for broken handlers, otherwise nasty to debug:
+                if ((goodValue == null) || raw.isInstance(goodValue)) {
+                    return goodValue;
+                }
+                throw JsonMappingException.from(p, _format(
+"DeserializationProblemHandler.handleWeirdNativeValue() for type %s returned value of type %s",
+targetType, goodValue.getClass()));
+            }
+        }
+        throw weirdNativeValueException(badValue, raw);
+    }
+
     /**
      * Method that deserializers should call if they fail to instantiate value
      * due to lack of viable instantiator (usually creator, that is, constructor
@@ -1531,6 +1553,24 @@ public JsonMappingException weirdNumberException(Number value, Class<?> instClas
                 value, instClass);
     }
 
+    /**
+     * Helper method for constructing exception to indicate that input JSON
+     * token of type "native value" (see {@link JsonToken#VALUE_EMBEDDED_OBJECT})
+     * is of incompatible type (and there is no delegating creator or such to use)
+     * and can not be used to construct value of specified type (usually POJO).
+     * Note that most of the time this method should NOT be called; instead,
+     * {@link #handleWeirdNativeValue} should be called which will call this method
+     *
+     * @since 2.9
+     */
+    public JsonMappingException weirdNativeValueException(Object value, Class<?> instClass)
+    {
+        return InvalidFormatException.from(_parser, String.format(
+"Cannot deserialize value of type %s from native value (`JsonToken.VALUE_EMBEDDED_OBJECT`) of type %s: incompatible types",
+            ClassUtil.nameOf(instClass), ClassUtil.classNameOf(value)),
+                value, instClass);
+    }
+
     /**
      * Helper method for constructing instantiation exception for specified type,
      * to indicate problem with physically constructing instance of

src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializerBase.java

@@ -1459,10 +1459,19 @@ public Object deserializeFromEmbedded(JsonParser p, DeserializationContext ctxt)
                 return bean;
             }
         }
-
         // TODO: maybe add support for ValueInstantiator, embedded?
-        
-        return p.getEmbeddedObject();
+
+        // 26-Jul-2017, tatu: related to [databind#1711], let's actually verify assignment
+        //    compatibility before returning. Bound to catch misconfigured cases and produce
+        //    more meaningful exceptions.
+        Object value = p.getEmbeddedObject();
+        if (value != null) {
+            if (!_beanType.getClass().isInstance(value)) {
+                // allow this to be handled...
+                value = ctxt.handleWeirdNativeValue(_beanType, value, p);
+            }
+        }
+        return value;
     }
 
     /**

src/main/java/com/fasterxml/jackson/databind/deser/DeserializationProblemHandler.java

@@ -127,8 +127,8 @@ public Object handleWeirdKey(DeserializationContext ctxt,
      *    to indicate type of failure unless handler produces key to use
      *
      * @return Either {@link #NOT_HANDLED} to indicate that handler does not know
-     *    what to do (and exception may be thrown), or value to use as key (possibly
-     *    <code>null</code>
+     *    what to do (and exception may be thrown), or value to use as (possibly
+     *    <code>null</code>)
      *
      * @since 2.8
      */
@@ -161,14 +161,41 @@ public Object handleWeirdStringValue(DeserializationContext ctxt,
      *    to indicate type of failure unless handler produces key to use
      *
      * @return Either {@link #NOT_HANDLED} to indicate that handler does not know
-     *    what to do (and exception may be thrown), or value to use as key (possibly
-     *    <code>null</code>
+     *    what to do (and exception may be thrown), or value to use as (possibly
+     *    <code>null</code>)
      *
      * @since 2.8
      */
     public Object handleWeirdNumberValue(DeserializationContext ctxt,
-            Class<?> targetType, Number valueToConvert,
-            String failureMsg)
+            Class<?> targetType, Number valueToConvert, String failureMsg)
+        throws IOException
+    {
+        return NOT_HANDLED;
+    }
+
+    /**
+     * Method called when an embedded (native) value ({@link JsonToken#VALUE_EMBEDDED_OBJECT})
+     * cannot be converted directly into expected value type (usually POJO).
+     * Handler may choose to do one of 3 things:
+     *<ul>
+     * <li>Indicate it does not know what to do by returning {@link #NOT_HANDLED}
+     *  </li>
+     * <li>Throw a {@link IOException} to indicate specific fail message (instead of
+     *    standard exception caller would throw
+     *  </li>
+     * <li>Return actual converted value (of type <code>targetType</code>) to use as
+     *    replacement, and continue processing.
+     *  </li>
+     * </ul>
+     *
+     * @return Either {@link #NOT_HANDLED} to indicate that handler does not know
+     *    what to do (and exception may be thrown), or value to use (possibly
+     *    <code>null</code>)
+     *
+     * @since 2.9
+     */
+    public Object handleWeirdNativeValue(DeserializationContext ctxt,
+            JavaType targetType, Object valueToConvert, JsonParser p)
         throws IOException
     {
         return NOT_HANDLED;