Using different projection for each entity subtype [DATAREST-739]

Anton Koscejev opened DATAREST-739 and commented

Currently it's not possible to use projections with inheritance to manage which fields from each sub-type are shown.

Consider example from DATAREST-344 but with excerpt projections:

@Entity
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="type")
@JsonTypeInfo(use=JsonTypeInfo.Id.NAME, include=JsonTypeInfo.As.PROPERTY, property="type")
public abstract class Message implements Identifiable<UUID> { ... }

@Entity
@DiscriminatorValue("TEXT")
@JsonTypeName("TEXT")
public class TextMessage extends Message { ... }

@Entity
@DiscriminatorValue("TODO")
@JsonTypeName("TODO")
public class TodoMessage extends Message { ... }

@Projection(name = "summary", types = TodoMessage.class)
public class TodoMessageSummary { ... }

@Projection(name = "summary", types = TextMessage.class)
public class TextMessageSummary { ... }

public interface MessageRepo extends JpaRepository<Message, UUID> { ... }

@RepositoryRestResource(excerptProjection = TodoMessageSummary.class)
public interface TodoMessageRepo extends JpaRepository<Message, UUID> { ... }

@RepositoryRestResource(excerptProjection = TextMessageSummary.class)
public interface TextMessageRepo extends JpaRepository<TextMessage, UUID> { ... }

First issue: how to define an excerpt projection for MessageRepo to use TodoMessageSummary for TodoMessage entities and TextMessageSummary for TextMessage?

Second issue: how to define projection for another entity that has a Message field? Let's say you have the following:

@Projection(name = "summary", types = Dashboard.class)
public class DashboardSummary {
  List<Message> getMessages();
}

Using List<Message> works as expected: you get a list of messages, where each message could be TodoMessage or TextMessage and will have fields appropriate for its type. However, I want manage which fields are show for each sub-type of Message. (Using nexted projections for collections was introduced in DATAREST-394.) I cannot do this by specifying TodoMessageSummary or TextMessageSummary. What would I need to specify to make Spring Data REST choose TodoMessageSummary if it's a TodoMessage and TextMessageSummary if it's a TextMessage?

Affects: 2.4.1 (Gosling SR1), 3.1.9 (Lovelace SR9)

Issue Links:

• DATAREST-747 ProjectionDefinitionConfiguration does not select projection for most concrete type
  ("depends on")

10 votes, 9 watchers