Can not serialize java 8 stream with StackOverflowError

[ilumer]

I try to use stream api to get all elements recursive, but this method throw a infinite recursion (StackOverflowError)。I can not find problem in my code，I try to build a small code to reproduce this scenario，I find the reason that produce error is I register the Jdk8Module. If i remove this module , it work right. Can you give me some suggestions, thank you.

• java version 1.8.0_162
• jackson-databind 2.9.0

• jackson-datatype-jdk8 2.9.0

  public class Store {
  public static void main(String[] args) {
  ObjectMapper objectMapper = new ObjectMapper().registerModule(new Jdk8Module());
  ResponseData responseData = new ResponseData();
  List<a> list = new ArrayList<>();
  list.add(new a());
  responseData.data = list;
  try {
      responseData.getData();
    System.out.println(objectMapper.writeValueAsString(list));
  } catch (JsonProcessingException e) {
    System.out.println(e.toString());
  }
  }
  
  static class ResponseData {
  private List<a> data;
  
  public List<a> getData() {
    return data;
  }
  }
  
  static class a {
  
  private List<a> ele;
  
  public Stream<a> getEleStream() {
    if (CollectionUtils.isEmpty(ele)) {
      return Stream.of(this);
    } else {
      return Stream.concat(
          Stream.of(this), ele.stream().flatMap(a::getEleStream));
    }
  }
  }
  }

[cowtowncoder]

But isn't your content here cyclic, with a.elStream pointing back to a? That would lead to infinite recursion. I am not sure how else it should work; either it is necessary to prevent cyclic references with @JsonIgnore on right fields, or to use Object Id handling (@JsonIdentityInfo).

As to including jackson-datatype-jdk8: without it Stream is only seen as POJO, probably with parallel (from boolean isParallel()).

[ilumer]

Thanks for replaying，I just think Stream is only seen as POJO, so it should not throw StackOverflowError. I can not find that it handle the stream specially, I should read the doc more carefully.