Map JsonArray to List<Pojo> using Jackson ObjectMapper

Question

I need to convert a Json array represented as String to List<Pojo> using Jackson's ObjectMapper.

Here is what I did which doesn't really work:

public static <T> List<T> toList(String jsonString, Class<T> clazzType) {

    try {
      List<T> list = OBJECT_MAPPER.readValue(jsonString, new TypeReference<List<T>>() {});

      return list;

    } catch (IOException ex) {
      throw new RuntimeException(ex);
    }
  }

It returns an object with an internal list but doesn't really build the expected list of Pojos. I saw some attempts to use Reflection but I'm trying to keep it pure Jackson.

Any idea??

Answer 1

You can use the TypeFactory to create a CollectionLikeType. For example like this:

ObjectMapper objectMapper = new ObjectMapper();

CollectionLikeType collectionLikeType = objectMapper.getTypeFactory()
    .constructCollectionLikeType(List.class, String.class);

List<String> o = objectMapper.readValue("[\"hello\"]", collectionLikeType);

assertEquals(o, List.of("hello"));