DTO projection with properties from joined entities

It would be nice to be able to project also properties from joined entity into DTO.

Imagine that I have two entities:

@Entity
public class Recipe {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String name;
    private String sourceUrl;
    @ElementCollection
    private List<String> steps;
    private LocalDateTime createdOn;
// + getters and setters
}

@Entity
public class ParseError implements Serializable {
    @Id
    @ManyToOne(fetch = FetchType.LAZY)
    private Recipe recipe;
    @Id
    private String problemArea;
    private String message;
// + getters and setters
}

Then I would like to have DTO for ParseError like this:

@Introspected
public class ParseErrorDto {
    private Integer recipeId;
    private String recipeName;
    private String problemArea;
    private String message;
// + getters and setters
}

Where the framework can translate recipeId DTO property into entity path recipe.id. If it is too complex to resolve it automatically then at least using @Value("#{recipe.id}") annotation as it is in Spring Data.

Or it can be like this:

@Introspected
public class ParseErrorDto {
    private RecipeDto recipe;
    private ParseError.ProblemArea problemArea;
    private String message;
    // + getters and setters
}

Where Recipe recipe property from entity is mapped into RecipeDto recipe property in DTO. And DTO for Recipe entity can look like this:

@Introspected
public class RecipeDto {
    private Integer id;
    private String name;
    // + getters and setters
}

Does it make sense? Would it be possible?

Thank you.

[graemerocher]

It does make sense and would potentially be possible. Thanks for the feedback.

[graemerocher]

It’s hard 😄

Will take another stab soon