I was trying to serialize and deserialize the bidirectional relationship in my database. I’ve used @JsonBackReference and @JsonManagedReference to do just that…I have 2 tables (classes): Question and QuestionGroup. One questionGroup can have multiple questions and many questions can be a part of one questionGroup. When I tried sending a GET request (while annotating the proper fields with managed and back reference), the response I got back was serialized perfectly. Just the way I wanted. But when I tried sending POST request I got the error in the title: