How to register a custom list serializer with Spring Boot / Jackson

public class LanguageString {

Locale locale;
String value;
"de": "hallo",
"en": "hello",
"fr": "bonjour"
  • Annotate every field that you want to use that serializer with @JsonSerializer(use = YourCustomSerializerClass.class). This is not a choice for us as we simply have the List<LanguageString> everywhere and we want to set a default behaviour for it.
  • Register your custom serializer with Jackson config and the data type. This normally works fine without collection type. After quite a bit of struggling to make it work and still failed, I came across the comment in Jackson’s
* Method for adding serializer to handle values of specific type.
* WARNING! Type matching only uses type-erased {
@code Class} and should NOT
* be used when registering serializers for generic types like
* {
@link java.util.Collection} and {@link java.util.Map}.
public class CollectionTypeJsonSerializer extends SimpleSerializers {

public JsonSerializer<?> findCollectionSerializer(SerializationConfig config,
CollectionType type,
BeanDescription beanDesc,
TypeSerializer elementTypeSerializer,
JsonSerializer<Object> elementValueSerializer) {
//if the collection is of type LanguageString, then use custom collection serializer
if (isLanguageStringListType(type)) {
return new LanguageStringListSerializer();

return findSerializer(config, type, beanDesc);

private boolean isLanguageStringListType(CollectionType type) {
CollectionType languageStringArrayListType = TypeFactory.defaultInstance()
.constructCollectionType(ArrayList.class, LanguageString.class);

CollectionType languageStringListType = TypeFactory.defaultInstance()
.constructCollectionType(List.class, LanguageString.class);

return (type.equals(languageStringListType) || type.equals(languageStringArrayListType));
public class JacksonConfig {
public ObjectMapper jsonObjectMapper() {
ArrayList<Module> modules = new ArrayList<>();

//CollectionType Serialization
SimpleModule collectionTypeSerializerModule = new SimpleModule();
collectionTypeSerializerModule.setSerializers(new CollectionTypeJsonSerializer());

return Jackson2ObjectMapperBuilder.json()



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