Allow default enums with @JsonCreator (#4979)

Author: dropofwill

release-notes/CREDITS-2.x

@@ -1918,3 +1918,7 @@ Floris Westerman (@FWest98)
 Joren Inghelbrecht (@jin-harmoney)
  * Contributed #4953: Allow clearing all caches to avoid classloader leaks
   (2.19.0)
+
+Will Paul (@dropofwill)
+ * Contributed #4979: Allow default enums with `@JsonCreator`
+  (2.19.0)

release-notes/VERSION-2.x

@@ -66,6 +66,8 @@ Project: jackson-databind
  (fix by Joo-Hyuk K)
 #4963: Serializing `Map.Entry` as Bean with `@JsonFormat.shape = Shape.OBJECT`
   fails on JDK 17+
+#4979: Allow default enums with `@JsonCreator`
+ (contributed by Will P)
 #4997: `ObjectNode` put methods should do null check for key
 #5006: Add `MapperFeature.REQUIRE_HANDLERS_FOR_JAVA8_OPTIONALS` to prevent
   failure of `java.util.Optional` (de)serialization without Java 8 module

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

@@ -1087,7 +1087,9 @@ public JsonDeserializer<?> createEnumDeserializer(DeserializationContext ctxt,
 "Invalid `@JsonCreator` annotated Enum factory method [%s]: needs to return compatible type",
 factory.toString()));
                     }
-                    deser = EnumDeserializer.deserializerForCreator(config, enumClass, factory, valueInstantiator, creatorProps);
+                    deser = EnumDeserializer.deserializerForCreator(
+                        config, enumClass, factory, valueInstantiator, creatorProps,
+                        constructEnumResolver(enumClass, config, beanDesc));
                     break;
                 }
             }

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

@@ -147,20 +147,20 @@ protected EnumDeserializer(EnumDeserializer base, Boolean caseInsensitive) {
     }
 
     /**
-     * @deprecated Since 2.9
-     */
-    @Deprecated
-    public EnumDeserializer(EnumResolver byNameResolver) {
-        this(byNameResolver, null);
-    }
-
-    /**
-     * @deprecated Since 2.8
+     * Factory method used when Enum instances are to be deserialized
+     * using a creator (static factory method)
+     *
+     * @return Deserializer based on given factory method
+     *
+     * @since 2.8
+     * @deprecated Since 2.19
      */
     @Deprecated
     public static JsonDeserializer<?> deserializerForCreator(DeserializationConfig config,
-            Class<?> enumClass, AnnotatedMethod factory) {
-        return deserializerForCreator(config, enumClass, factory, null, null);
+             Class<?> enumClass, AnnotatedMethod factory,
+             ValueInstantiator valueInstantiator, SettableBeanProperty[] creatorProps) {
+        return deserializerForCreator(config, enumClass, factory, valueInstantiator,
+                creatorProps, null);
     }
 
     /**
@@ -169,19 +169,19 @@ public static JsonDeserializer<?> deserializerForCreator(DeserializationConfig c
      *
      * @return Deserializer based on given factory method
      *
-     * @since 2.8
+     * @since 2.19
      */
     public static JsonDeserializer<?> deserializerForCreator(DeserializationConfig config,
             Class<?> enumClass, AnnotatedMethod factory,
-            ValueInstantiator valueInstantiator, SettableBeanProperty[] creatorProps)
+            ValueInstantiator valueInstantiator, SettableBeanProperty[] creatorProps,
+            EnumResolver byNameResolver)
     {
         if (config.canOverrideAccessModifiers()) {
             ClassUtil.checkAndFixAccess(factory.getMember(),
                     config.isEnabled(MapperFeature.OVERRIDE_PUBLIC_ACCESS_MODIFIERS));
         }
-        return new FactoryBasedEnumDeserializer(enumClass, factory,
-                factory.getParameterType(0),
-                valueInstantiator, creatorProps);
+        return new FactoryBasedEnumDeserializer(enumClass, factory, factory.getParameterType(0),
+            valueInstantiator, creatorProps, byNameResolver);
     }
 
     /**

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

@@ -15,6 +15,7 @@
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
 import com.fasterxml.jackson.databind.type.LogicalType;
 import com.fasterxml.jackson.databind.util.ClassUtil;
+import com.fasterxml.jackson.databind.util.EnumResolver;
 
 /**
  * Deserializer that uses a single-String static factory method
@@ -35,6 +36,9 @@ class FactoryBasedEnumDeserializer
     protected final ValueInstantiator _valueInstantiator;
     protected final SettableBeanProperty[] _creatorProps;
 
+    // @since 2.19
+    protected final Enum<?> _defaultValue;
+
     protected final boolean _hasArgs;
 
     /**
@@ -44,8 +48,23 @@ class FactoryBasedEnumDeserializer
      */
     private transient volatile PropertyBasedCreator _propCreator;
 
+    /**
+     * @since 2.8
+     * @deprecated since 2.19
+     */
+    @Deprecated
     public FactoryBasedEnumDeserializer(Class<?> cls, AnnotatedMethod f, JavaType paramType,
             ValueInstantiator valueInstantiator, SettableBeanProperty[] creatorProps)
+    {
+        this(cls, f, paramType, valueInstantiator, creatorProps, null);
+    }
+
+    /**
+     * @since 2.19
+     */
+    public FactoryBasedEnumDeserializer(Class<?> cls, AnnotatedMethod f, JavaType paramType,
+            ValueInstantiator valueInstantiator, SettableBeanProperty[] creatorProps,
+            EnumResolver enumResolver)
     {
         super(cls);
         _factory = f;
@@ -56,6 +75,7 @@ public FactoryBasedEnumDeserializer(Class<?> cls, AnnotatedMethod f, JavaType pa
         _deser = null;
         _valueInstantiator = valueInstantiator;
         _creatorProps = creatorProps;
+        _defaultValue = (enumResolver == null) ? null : enumResolver.getDefaultValue();
     }
 
     /**
@@ -70,6 +90,7 @@ public FactoryBasedEnumDeserializer(Class<?> cls, AnnotatedMethod f)
         _deser = null;
         _valueInstantiator = null;
         _creatorProps = null;
+        _defaultValue = null;
     }
 
     protected FactoryBasedEnumDeserializer(FactoryBasedEnumDeserializer base,
@@ -80,6 +101,7 @@ protected FactoryBasedEnumDeserializer(FactoryBasedEnumDeserializer base,
         _hasArgs = base._hasArgs;
         _valueInstantiator = base._valueInstantiator;
         _creatorProps = base._creatorProps;
+        _defaultValue = base._defaultValue;
 
         _deser = deser;
     }
@@ -198,7 +220,14 @@ public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOEx
         } catch (Exception e) {
             Throwable t = ClassUtil.throwRootCauseIfIOE(e);
             if (t instanceof IllegalArgumentException) {
-                // [databind#1642]:
+                // [databind#4979]: unknown as default
+                if (ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE)) {
+                    // ... only if we DO have a default
+                    if (_defaultValue != null) {
+                        return _defaultValue;
+                    }
+                }
+                // [databind#1642]: unknown as null
                 if (ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL)) {
                     return null;
                 }

src/test/java/com/fasterxml/jackson/databind/deser/creators/EnumCreatorTest.java

@@ -125,7 +125,8 @@ public JsonDeserializer<?> findEnumDeserializer(final Class<?> type, final Deser
                 for (AnnotatedMethod am : factoryMethods) {
                     final JsonCreator creator = am.getAnnotation(JsonCreator.class);
                     if (creator != null) {
-                        return EnumDeserializer.deserializerForCreator(config, type, am, null, null);
+                        return EnumDeserializer.deserializerForCreator(
+                            config, type, am, null, null, null);
                     }
                 }
             }

src/test/java/com/fasterxml/jackson/databind/deser/enums/EnumDeserializationTest.java

@@ -161,7 +161,7 @@ static enum EnumWithDefaultAnnoAndConstructor {
     }
 
     static enum StrictEnumCreator {
-        A, B;
+        A, B, @JsonEnumDefaultValue UNKNOWN;
 
         @JsonCreator public static StrictEnumCreator fromId(String value) {
             for (StrictEnumCreator e: values()) {
@@ -453,7 +453,7 @@ public void testAllowUnknownEnumValuesReadAsNull() throws Exception
         assertNull(reader.forType(TestEnum.class).readValue(" 4343 "));
     }
 
-    // Ability to ignore unknown Enum values:
+    // Ability to ignore unknown Enum values as null:
 
     // [databind#1642]
     @Test
@@ -483,6 +483,19 @@ public void testAllowUnknownEnumValuesAsMapKeysReadAsNull() throws Exception
         assertTrue(result.map.containsKey(null));
     }
 
+    // Ability to ignore unknown Enum values as a defined default:
+
+    // [databind#4979]
+    @Test
+    public void testAllowUnknownEnumValuesReadAsDefaultWithCreatorMethod4979() throws Exception
+    {
+        ObjectReader reader = MAPPER.reader(
+            DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE);
+        assertEquals(
+            StrictEnumCreator.UNKNOWN,
+            reader.forType(StrictEnumCreator.class).readValue("\"NO-SUCH-VALUE\""));
+    }
+
     @Test
     public void testDoNotAllowUnknownEnumValuesAsMapKeysWhenReadAsNullDisabled() throws Exception
     {