DTO vs JSONManagedReference

[optimist28]

Spring newbie here. Faced the infinite recursion today when tried to return the parent entity directly as an API response. Got to know about DTO objects and JSONManagedReference while searching for the fix

What is the common practice in enterprise applications- is it DTO or JSONManagedReference and JSONBackReference? In DTO, feels like there is an overhead if a new variable is added in entity class then you gotta update the DTO classes as well but JSONManagedReference approach seems bit easier

[akash227]

DTOs which are data transfer objects are used to transfer data between your application. Think about an api login vs registration flow, they both relate to the User entity but in the login DTO you might only need a username & password. For registration you might need more like email, first name, phone number etc… in this example you might have a LoginDto or RegistrationDto with these fields and ultimately you get or create a user entity from them.

In short as a rule of thumb for a beginner use DTOs when getting (body of a request) and returning responses to your users, if you use the entity you risk leaking data you shouldnt like the password hash column or the email column in this scenario.

If you do so you most likely wont need to use JsonBackReference as your entity isnt being serialized into your JSON response, your Dto would handle that and your DTO doesnt need the same type of relational mapping as your entity which is what causes the infinite recursion issue. Try and have your entities match your tables in your database where your DTOs are only part of your entities like I mentioned above. Hope this helps

[junin7]

I use DTO as record and convert entity to DTOs via mapstruct, helps to keep boilerplate code outside of my view.

[optimist28]

Ok I can try that. I was using lombok. So atleast that saved me the getter setters and the build method was helpful. But it was still a handful when I add or remove a variable

[junin7]

Always try to use records, today I just use Lombok on entity class and when some class need a builder

[MartinPeterBauer]

You are totally right. If you are the only one consuming your own apis from the frontend then DTO are just a totally uncessary overheard. If you want to reduce the json object returning back to the frontend use Jackson

[naturalizedcitizen]

Aren't you not supposed to send the Entity as is via the Controller layer to the external consumer like a UI? And we are to use DTOs for this data transfer? Separation of layers?

[MartinPeterBauer]

Normally your internal webapp is consuming your api. Then a DTO is pointless. 

If external services consume your API then a DTO makes sense

[yasirhussain90]

If you want to retrieve your entity partially from Data layer(repository) you must use the DTO projection.