Issue-4214: Use EnumSetSerializer, if property is referring EnumSet at runtime

Author: Durga, V H V Sekhar

src/main/java/com/fasterxml/jackson/databind/ser/BeanPropertyWriter.java

@@ -5,6 +5,7 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.lang.reflect.Type;
+import java.util.EnumSet;
 import java.util.HashMap;
 
 import com.fasterxml.jackson.annotation.JsonInclude;
@@ -20,6 +21,7 @@
 import com.fasterxml.jackson.databind.ser.impl.PropertySerializerMap;
 import com.fasterxml.jackson.databind.ser.impl.UnwrappingBeanPropertyWriter;
 import com.fasterxml.jackson.databind.ser.std.BeanSerializerBase;
+import com.fasterxml.jackson.databind.ser.std.EnumSetSerializer;
 import com.fasterxml.jackson.databind.util.Annotations;
 import com.fasterxml.jackson.databind.util.ClassUtil;
 import com.fasterxml.jackson.databind.util.NameTransformer;
@@ -702,7 +704,10 @@ public void serializeAsField(Object bean, JsonGenerator gen,
         }
         // then find serializer to use
         JsonSerializer<Object> ser = _serializer;
-        if (ser == null) {
+		if (ser == null || (value instanceof EnumSet && ser.getClass() != EnumSetSerializer.class)) {
+			// if value instance of EnumSet, use EnumSetSerializer for EnumSet instead of
+			// generic CollectionSerializer, since de-serialization uses EnumSetDeserializer,
+			// if property value is of type EnumSet
             Class<?> cls = value.getClass();
             PropertySerializerMap m = _dynamicSerializers;
             ser = m.serializerFor(cls);

src/test/java/com/fasterxml/jackson/databind/ser/enums/EnumSetSerializationTest.java

@@ -0,0 +1,69 @@
+package com.fasterxml.jackson.databind.ser.enums;
+
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.util.EnumSet;
+import java.util.Set;
+
+import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
+import com.fasterxml.jackson.annotation.PropertyAccessor;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper.DefaultTyping;
+import com.fasterxml.jackson.databind.jsontype.BasicPolymorphicTypeValidator;
+
+public class EnumSetSerializationTest extends BaseMapTest {
+
+	static enum MyEnum {
+		ITEM_A, ITEM_B;
+	}
+
+	static class EnumSetHolder {
+		private Set<MyEnum> enumSet; // use Set instead of EnumSet for type of this
+
+		public Set<MyEnum> getEnumSet() {
+			return enumSet;
+		}
+
+		public void setEnumSet(Set<MyEnum> enumSet) {
+			this.enumSet = enumSet;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (!(o instanceof EnumSetHolder)) {
+				return false;
+			}
+			EnumSetHolder eh = (EnumSetHolder) o;
+			if (eh == this) {
+				return true;
+			}
+			if (enumSet == null) {
+				if (eh.getEnumSet() == null) {
+					return true;
+				} else {
+					return false;
+				}
+			} else {
+				if (eh.getEnumSet() == null) {
+					return false;
+				}
+				return enumSet.containsAll(eh.getEnumSet());
+			}
+		}
+	}
+
+	public void testSerialization() throws Exception {
+		ObjectMapper mapper = jsonMapperBuilder().build()
+				.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+				// this type information is needed in json string, for this test
+				.activateDefaultTyping(BasicPolymorphicTypeValidator.builder().allowIfBaseType(Object.class).build(),
+						DefaultTyping.EVERYTHING);
+
+		EnumSetHolder enumSetHolder = new EnumSetHolder();
+		enumSetHolder.setEnumSet(EnumSet.allOf(MyEnum.class));
+		String jsonStr = mapper.writeValueAsString(enumSetHolder);
+		EnumSetHolder result = mapper.readValue(jsonStr, EnumSetHolder.class);
+		assertEquals(result, enumSetHolder);
+	}
+}