Spring Inject @PathVariable variables in argument DTO

Hi, I have this code in one of my controllers:

  @PutMapping("{id}")
  public EntityDTO update(@PathVariable("id") String id, @RequestBody EntityDTO entityDTO) {
    entityDTO.setId(id);
    Entity entity = entityMapper.map(entityDTO);
    Entity updated = entityService.save(entity);
    return entityDTOMapper.map(updated);
  }

I want to avoid the entityDTO.setId(id); line and add the id to the entityDTO in an cleaner way, but I didn't find a suitable approach in Spring.

Using an argument resolver is a mess for such a simple task, but maybe it can be achieved injecting the id in entityDTO in the following way:

public class EntityDTO {

  @PathVariable("id")
  private String id;
  ...
}

Validation stuff should occur once the DTO is constructed.

I did a lot of research, and I found a lot of users wanting this feature or facing this problem of packaging the whole thing (body + query parameters) in a DTO before mapping to entity.

Comment From: mfolnovic

I've asked about this on SO 3 years ago: https://stackoverflow.com/questions/57905483/combining-pathvariable-and-requestbody. I'm still interested in this feature. :)

One extra point of view would be validation constraints, e.g. unique constraint on some field (on update, you also need to know id to implement it correctly).

Comment From: lbkulinski

Any update on this? It is something I would like to see as well. Thanks!

Comment From: rstoyanchev

This is a duplicate of #23618. You can also see some takes on this in https://github.com/spring-projects/spring-framework/issues/21770#issuecomment-453476735.