Feature : add EnumFeature.WRITE_ENUMS_TO_LOWERCASE #3053 #3054 (#3776)

Author: JooHyukKim

src/main/java/com/fasterxml/jackson/databind/cfg/EnumFeature.java

@@ -22,8 +22,16 @@ public enum EnumFeature implements DatatypeFeature
      *
      * @since 2.15
      */
-    READ_ENUM_KEYS_USING_INDEX(false)
-    ;
+    READ_ENUM_KEYS_USING_INDEX(false),
+
+    /**
+     * Feature that determines standard serialization mechanism used for
+     * Enum values: if enabled, return value of <code>Enum.name().toLowerCase()</code>
+     * is used; if disabled, return value of <code>Enum.name()</code> is used.
+     *<p>
+     * Feature is disabled by default.
+     */
+    WRITE_ENUMS_TO_LOWERCASE(false);
 
     private final static int FEATURE_INDEX = DatatypeFeatures.FEATURE_INDEX_ENUM;
 

src/main/java/com/fasterxml/jackson/databind/util/EnumValues.java

@@ -4,6 +4,7 @@
 
 import com.fasterxml.jackson.core.SerializableString;
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.cfg.EnumFeature;
 import com.fasterxml.jackson.databind.cfg.MapperConfig;
 
 /**
@@ -56,6 +57,9 @@ public static EnumValues constructFromName(MapperConfig<?> config, Class<Enum<?>
             if (name == null) {
                 name = en.name();
             }
+            if (config.isEnabled(EnumFeature.WRITE_ENUMS_TO_LOWERCASE)) {
+                name = name.toLowerCase();
+            }
             textual[en.ordinal()] = config.compileString(name);
         }
         return construct(enumClass, textual);

src/test/java/com/fasterxml/jackson/databind/ser/jdk/EnumSerializationTest.java

@@ -8,6 +8,7 @@
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.annotation.JsonSerialize;
+import com.fasterxml.jackson.databind.cfg.EnumFeature;
 import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.databind.ser.std.StdSerializer;
@@ -330,6 +331,25 @@ public void testEnumWithJsonKey() throws Exception
             = Collections.singletonMap(EnumWithJsonKey.A, EnumWithJsonKey.B);
         assertEquals(a2q("{'key:a':'value:b'}"), MAPPER.writeValueAsString(input2));
     }
+
+    public void testEnumFeature_WRITE_ENUMS_TO_LOWERCASE_isDisabledByDefault() {
+        ObjectReader READER = MAPPER.reader();
+        assertFalse(READER.isEnabled(EnumFeature.WRITE_ENUMS_TO_LOWERCASE));
+        assertFalse(READER.without(EnumFeature.WRITE_ENUMS_TO_LOWERCASE)
+            .isEnabled(EnumFeature.WRITE_ENUMS_TO_LOWERCASE));
+    }
+
+    public void testEnumFeature_WRITE_ENUMS_TO_LOWERCASE() throws Exception {
+        ObjectMapper m = jsonMapperBuilder()
+            .configure(EnumFeature.WRITE_ENUMS_TO_LOWERCASE, true)
+            .build();
+        assertEquals("\"b\"", m.writeValueAsString(TestEnum.B));
+
+        // [databind#749] but should also be able to dynamically disable
+        assertEquals("\"B\"",
+            m.writer().without(EnumFeature.WRITE_ENUMS_TO_LOWERCASE)
+                .writeValueAsString(LowerCaseEnum.B));
+    }
 }
 
 // [JACKSON-757], non-inner enum

src/test/java/com/fasterxml/jackson/databind/util/EnumValuesTest.java

@@ -6,6 +6,7 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationConfig;
 import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.cfg.EnumFeature;
 
 public class EnumValuesTest extends BaseMapTest
 {
@@ -64,4 +65,17 @@ public void testEnumResolver()
         assertEquals(ABC.B, enums.get(1));
         assertEquals(ABC.C, enums.get(2));
     }
+
+    @SuppressWarnings("unchecked")
+    public void testConstructFromNameLowerCased() {
+        SerializationConfig cfg = MAPPER.getSerializationConfig()
+            .with(EnumFeature.WRITE_ENUMS_TO_LOWERCASE);
+        Class<Enum<?>> enumClass = (Class<Enum<?>>)(Class<?>) ABC.class;
+        EnumValues values = EnumValues.construct(cfg, enumClass);
+        assertEquals("a", values.serializedValueFor(ABC.A).toString());
+        assertEquals("b", values.serializedValueFor(ABC.B).toString());
+        assertEquals("c", values.serializedValueFor(ABC.C).toString());
+        assertEquals(3, values.values().size());
+        assertEquals(3, values.internalMap().size());
+    }
 }