Same/different DTO object in create, update and get rest end points?

Question

Consider following UserDTO class and UserController exposing endpoints to create, update and get User.

Having the id property in the UserDTO class does not make sense for create and update. If I use swagger or another auto generated API documentation then it shows that the id can be passed in create end point. But the system does not use it as ids are generated internally.

If I look at get then probably I can get rid of the id property but it is certainly required in a list user end point.

I was thinking of returning internal User domain object in get/list end points. This way I can then get rid of id property form UserDTO class.

Is there any better option I can employ for this?

public class UserDTO {
    private int id;
    private String name;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

@RestController
@RequestMapping(value = "/users", produces = MediaType.APPLICATION_JSON_VALUE)
public class UserController {
    @RequestMapping(method = RequestMethod.POST)
    @ResponseBody
    public ResponseEntity<Void> create(@RequestBody UserDTO user) {
    }

    @RequestMapping(value = "{id}", method = RequestMethod.GET)
    @ResponseBody
    public ResponseEntity<UserDTO> get(@PathVariable("id") int id) {
    }

    @RequestMapping(value = "{id}", method = RequestMethod.PUT)
    @ResponseBody
    public ResponseEntity<Void> update(@PathVariable("id") int id, @RequestBody UserDTO user) {
    }
}

This question may have been asked but I could not find. So excuse me for duplicate question.

Answer 1

Data Transfer Object (DTO) is a pattern that was created with a very well defined purpose: transfer data to remote interfaces, just like web services. This pattern fits very well in REST APIs and DTOs will give you more flexibility in the long run.

I would recommend using tailored classes for your endpoints, once REST resource representations don't need to have the same attributes as the persistence objects.

To avoid boilerplate code, you can use mapping frameworks such as MapStruct to map your REST API DTOs from/to your persistence objects.

For details on the benefits of using DTOs in REST APIs, check the following answers:

• Why you should use DTOs in your REST API
• Using tailored classes of request and response

To give your DTOs better names, check the following answer:

• Giving meaningful names to your DTOs

Answer 2

What's about creating two different interfaces :

interface UserDTO {

    public String getName ();

    public void setName (String name);

}

interface IdentifiableUserDTO extends UserDTO {

    public Long getId ();

    public void setId (Long id);

}


class DefaultUserDTO implements IdentifiableUserDTO {

}

and then use the Interface in your controller instead of the DTO class :

@RestController
@RequestMapping(value = "/users", produces = MediaType.APPLICATION_JSON_VALUE)
public class UserController {
    @RequestMapping(method = RequestMethod.POST)
    @ResponseBody
    public ResponseEntity<Void> create(@RequestBody IdentifiableUserDTO user) {
    }

    @RequestMapping(value = "{id}", method = RequestMethod.GET)
    @ResponseBody
    public ResponseEntity<UserDTO> get(@PathVariable("id") int id) {
    }

    @RequestMapping(value = "{id}", method = RequestMethod.PUT)
    @ResponseBody
    public ResponseEntity<Void> update(@PathVariable("id") int id, @RequestBody UserDTO user) {
    }
}