Work on #2539

Author: cowtowncoder

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

@@ -193,7 +193,7 @@ private JavaType _mapAbstractType2(DeserializationConfig config, JavaType type)
 
     /*
     /**********************************************************
-    /* JsonDeserializerFactory impl (partial): ValueInstantiators
+    /* DeserializerFactory impl (partial): ValueInstantiators
     /**********************************************************
      */
 
@@ -1108,7 +1108,7 @@ protected PropertyMetadata _getSetterInfo(DeserializationContext ctxt,
 
     /*
     /**********************************************************
-    /* JsonDeserializerFactory impl: array deserializers
+    /* DeserializerFactory impl: array deserializers
     /**********************************************************
      */
 
@@ -1154,7 +1154,7 @@ public JsonDeserializer<?> createArrayDeserializer(DeserializationContext ctxt,
 
     /*
     /**********************************************************************
-    /* JsonDeserializerFactory impl: Collection(-like) deserializers
+    /* DeserializerFactory impl: Collection(-like) deserializers
     /**********************************************************************
      */
 
@@ -1283,7 +1283,7 @@ public JsonDeserializer<?> createCollectionLikeDeserializer(DeserializationConte
 
     /*
     /**********************************************************
-    /* JsonDeserializerFactory impl: Map(-like) deserializers
+    /* DeserializerFactory impl: Map(-like) deserializers
     /**********************************************************
      */
 
@@ -1443,7 +1443,7 @@ public JsonDeserializer<?> createMapLikeDeserializer(DeserializationContext ctxt
 
     /*
     /**********************************************************
-    /* JsonDeserializerFactory impl: other types
+    /* DeserializerFactory impl: other types
     /**********************************************************
      */
 
@@ -1560,7 +1560,7 @@ public JsonDeserializer<?> createReferenceDeserializer(DeserializationContext ct
 
     /*
     /**********************************************************
-    /* JsonDeserializerFactory impl (partial): type deserializers
+    /* DeserializerFactory impl (partial): type deserializers
     /**********************************************************
      */
 
@@ -1616,13 +1616,13 @@ protected JsonDeserializer<?> findOptionalStdDeserializer(DeserializationContext
     {
         return OptionalHandlerFactory.instance.findDeserializer(type, ctxt.getConfig(), beanDesc);
     }
-    
+
     /*
     /**********************************************************
-    /* JsonDeserializerFactory impl (partial): key deserializers
+    /* DeserializerFactory impl (partial): key deserializers
     /**********************************************************
      */
-    
+
     @Override
     public KeyDeserializer createKeyDeserializer(DeserializationContext ctxt,
             JavaType type)
@@ -1718,6 +1718,44 @@ private KeyDeserializer _createEnumKeyDeserializer(DeserializationContext ctxt,
         return StdKeyDeserializers.constructEnumKeyDeserializer(enumRes);
     }
 
+    /*
+    /**********************************************************
+    /* DeserializerFactory impl: checking explicitly registered desers
+    /**********************************************************
+     */
+
+    @Override
+    public boolean hasExplicitDeserializerFor(DeserializationConfig config,
+            Class<?> valueType) {
+        // Yes, we handle all Enum types
+        if (Enum.class.isAssignableFrom(valueType)) {
+            return true;
+        }
+        // Numbers?
+        final String clsName = valueType.getName();
+        if (clsName.startsWith("java.")) {
+            if (Number.class.isAssignableFrom(valueType)) {
+                return NumberDeserializers.find(valueType, clsName) != null;
+            }
+            if ((valueType == CLASS_STRING)
+                    || (valueType == Boolean.class)
+                    || (valueType == EnumMap.class)
+                    || (valueType == AtomicReference.class)
+                    ) {
+                return true;
+            }
+            if (DateDeserializers.hasDeserializerFor(valueType)) {
+                return true;
+            }
+        } else if (clsName.startsWith("com.fasterxml.")) {
+            return JsonNode.class.isAssignableFrom(valueType)
+                   || (valueType == TokenBuffer.class);
+        } else {
+            return OptionalHandlerFactory.instance.hasDeserializerFor(valueType);
+        }
+        return false;
+    }
+
     /*
     /**********************************************************
     /* Extended API

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

@@ -201,4 +201,16 @@ public abstract KeyDeserializer createKeyDeserializer(DeserializationContext ctx
     public abstract TypeDeserializer findTypeDeserializer(DeserializationConfig config,
             JavaType baseType)
         throws JsonMappingException;
+
+    /**
+     * Method that can be used to check if databind module has deserializer
+     * for given (likely JDK) type: explicit meaning that it is not automatically
+     * generated for POJO.
+     *<p>
+     * This matches {@code Deserializers.Base.hasDeserializerFor(Class)} method.
+     *
+     * @since 2.11
+     */
+    public abstract boolean hasExplicitDeserializerFor(DeserializationConfig config,
+            Class<?> valueType);
 }

src/main/java/com/fasterxml/jackson/databind/deser/std/DateDeserializers.java

@@ -60,6 +60,11 @@ public static JsonDeserializer<?> find(Class<?> rawType, String clsName)
         return null;
     }
 
+    // @since 2.11
+    public static boolean hasDeserializerFor(Class<?> rawType) {
+        return _classNames.contains(rawType.getName());
+    }
+
     /*
     /**********************************************************
     /* Intermediate class for Date-based ones

src/main/java/com/fasterxml/jackson/databind/deser/std/NumberDeserializers.java

@@ -108,7 +108,7 @@ public static JsonDeserializer<?> find(Class<?> rawType, String clsName) {
         // should never occur
         throw new IllegalArgumentException("Internal error: can't find deserializer for "+rawType.getName());
     }
-    
+
     /*
     /**********************************************************
     /* Then one intermediate base class for things that have

src/main/java/com/fasterxml/jackson/databind/ext/OptionalHandlerFactory.java

@@ -146,7 +146,22 @@ public JsonDeserializer<?> findDeserializer(JavaType type, DeserializationConfig
         }
         return ((Deserializers) ob).findBeanDeserializer(type, config, beanDesc);
     }
-    
+
+    public boolean hasDeserializerFor(Class<?> valueType) {
+        if ((CLASS_DOM_NODE != null) && CLASS_DOM_NODE.isAssignableFrom(valueType)) {
+            return true;
+        }
+        if ((CLASS_DOM_DOCUMENT != null) && CLASS_DOM_DOCUMENT.isAssignableFrom(valueType)) {
+            return true;
+        }
+        String className = valueType.getName();
+        if (className.startsWith(PACKAGE_PREFIX_JAVAX_XML)
+                || hasSuperClassStartingWith(valueType, PACKAGE_PREFIX_JAVAX_XML)) {
+            return true;
+        }
+        return false;
+    }
+
     /*
     /**********************************************************
     /* Internal helper methods