JPA: Many to many relationship - JsonMappingException: Infinite recursion

Question

I\'m having trouble with a many to many relation with JPA. My code looks as follows:

The Sensor class:

@Entity
@Table(name = \"sensor\")
@Data
@NoArg         


        

Answer 1

When User serialized for the response, all getter methods of User's fields are called. So, User relational field sensorLinks's getter are also called to set value. This happened recursively. That's cause of infinite recursion.

It's better to not use Entity as a response. Create a DTO class for User then map User entity value into DTO then send response. Don't use any Enity class again into DTO then it will result same problem

For dynamically map one model to another you can use ModleMapper

public class UserDTO {
   //Fields you want to show in response & don't use enity class 
   private Set<LinkDTO> sensorLinks;
}
public class LinkDTO{
   //Fields you want to show in response &don't use enity class 
}


public User getUserByEmail(@PathVariable("email") String email) {
    User user = userRepository.findByEmail(email).orElse(null);
    UserDTO userDto = merge(user,UserDTO.class)
    return userDto;
}

public static <T> void merge(T source, T target) {
    ModelMapper modelMapper = new ModelMapper();
    modelMapper.getConfiguration().setMatchingStrategy(MatchingStrategies.STRICT);
    modelMapper.map(source, target);
  }

Answer 2

It's working! This post helped: https://stackoverflow.com/a/57111004/6296634

Seems that you should not use Lombok @Data in such cases.