feat: add custom NullValueSerializer initializer

Author: AnneMayor

src/main/java/org/springframework/data/redis/serializer/GenericJackson2JsonRedisSerializer.java

@@ -98,7 +98,7 @@ public GenericJackson2JsonRedisSerializer() {
 	 * @see ObjectMapper#activateDefaultTyping(PolymorphicTypeValidator, DefaultTyping, As)
 	 */
 	public GenericJackson2JsonRedisSerializer(@Nullable String classPropertyTypeName) {
-		this(classPropertyTypeName, JacksonObjectReader.create(), JacksonObjectWriter.create());
+		this(classPropertyTypeName, JacksonObjectReader.create(), JacksonObjectWriter.create(), null);
 	}
 
 	/**
@@ -118,11 +118,15 @@ public GenericJackson2JsonRedisSerializer(@Nullable String classPropertyTypeName
 	 * @since 3.0
 	 */
 	public GenericJackson2JsonRedisSerializer(@Nullable String classPropertyTypeName, JacksonObjectReader reader,
-			JacksonObjectWriter writer) {
+			JacksonObjectWriter writer, @Nullable StdSerializer<NullValue> nullValueSerializer) {
 
 		this(new ObjectMapper(), reader, writer, classPropertyTypeName);
 
-		registerNullValueSerializer(this.mapper, classPropertyTypeName);
+		if (nullValueSerializer == null) {
+			registerNullValueSerializer(this.mapper, classPropertyTypeName);
+		} else {
+			registerCustomNullValueSerializer(nullValueSerializer);
+		}
 
 		StdTypeResolverBuilder typer = TypeResolverBuilder.forEverything(this.mapper).init(JsonTypeInfo.Id.CLASS, null)
 				.inclusion(JsonTypeInfo.As.PROPERTY);
@@ -231,6 +235,10 @@ public static void registerNullValueSerializer(ObjectMapper objectMapper, @Nulla
 		objectMapper.registerModule(new SimpleModule().addSerializer(new NullValueSerializer(classPropertyTypeName)));
 	}
 
+	private void registerCustomNullValueSerializer(StdSerializer<NullValue> nullValueSerializer) {
+		this.mapper.registerModule(new SimpleModule().addSerializer(nullValueSerializer));
+	}
+
 	/**
 	 * Gets the configured {@link ObjectMapper} used internally by this {@link GenericJackson2JsonRedisSerializer} to
 	 * de/serialize {@link Object objects} as {@literal JSON}.

src/test/java/org/springframework/data/redis/serializer/GenericJackson2JsonRedisSerializerUnitTests.java

@@ -230,7 +230,7 @@ void shouldConsiderWriter() {
 		GenericJackson2JsonRedisSerializer serializer = new GenericJackson2JsonRedisSerializer((String) null,
 				JacksonObjectReader.create(), (mapper, source) -> {
 					return mapper.writerWithView(Views.Basic.class).writeValueAsBytes(source);
-				});
+				}, null);
 
 		byte[] result = serializer.serialize(user);
 
@@ -269,7 +269,7 @@ void shouldConsiderReader() {
 						return mapper.readerWithView(Views.Basic.class).forType(type).readValue(source);
 					}
 					return mapper.readValue(source, type);
-				}, JacksonObjectWriter.create());
+				}, JacksonObjectWriter.create(), null);
 
 		byte[] serializedValue = serializer.serialize(user);
 
@@ -420,7 +420,7 @@ void deserializesJavaTimeFrimBytes() {
 	}
 
 	@Test // GH-2601
-	public void internalObjectMapperCustomization() {
+	void internalObjectMapperCustomization() {
 
 		GenericJackson2JsonRedisSerializer serializer = new GenericJackson2JsonRedisSerializer();
 
@@ -438,14 +438,28 @@ public void internalObjectMapperCustomization() {
 	}
 
 	@Test // GH-2601
-	public void configureWithNullConsumerThrowsIllegalArgumentException() {
+	void configureWithNullConsumerThrowsIllegalArgumentException() {
 
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> new GenericJackson2JsonRedisSerializer().configure(null))
 			.withMessage("Consumer used to configure and customize ObjectMapper must not be null")
 			.withNoCause();
 	}
 
+	@Test
+	void customSerializeAndDeserializeNullValue() {
+
+		GenericJackson2JsonRedisSerializer serializer = new GenericJackson2JsonRedisSerializer();
+
+		NullValue nv = BeanUtils.instantiateClass(NullValue.class);
+
+		byte[] serializedValue = serializer.serialize(nv);
+		assertThat(serializedValue).isNotNull();
+
+		Object deserializedValue = serializer.deserialize(serializedValue);
+		assertThat(deserializedValue).isInstanceOf(NullValue.class);
+	}
+
 	private static void serializeAndDeserializeNullValue(GenericJackson2JsonRedisSerializer serializer) {
 
 		NullValue nv = BeanUtils.instantiateClass(NullValue.class);