Relationship mapping in Hibernate Java - save owning side entity
You configure the relation between User and Url correctly. It mainly complains when it saves an Url , its User is a new record.
The problem can be fixed if you save the User first :
User user = getCurrentUserDetails();
user.addRssUrl(rssUrl);
userRepository.save(user);
rssUrlRepository.save(rssUrl);
But since you already configure cascade is ALL for User 's Url , all JPA operations applied on User will automatically applied to its Url too , which means you can simply do :
User user = getCurrentUserDetails();
user.addRssUrl(rssUrl);
userRepository.save(user);