How to use optional attributes in Spring Data / Webflux - spring-data

Question

I´m trying to work with joins in Spring-Webflux. I have two tables, comments and votes.
My Comment Entity has an attribute named score, which is the calculated number of votes.
The problem is this score isn´t a field inside the database, but at the moment a transient marked field in the Comment Object which is calculated by my application with bad performance.
My goal is to calculate this with a Join and not in my Application.
My Problem is that Spring doesn´t map the score field because of the transient annotation, which is needed because other Operations (patch or update) doesn´t provide this score field.
My Repository looks like this:
#Repository
public interface CommentRepository extends ReactiveCrudRepository<Comment, UUID> {
#Query("SELECT C.*, COALESCE(SUM(v.vote), 0) as score FROM comment c LEFT JOIN vote v ON c.id = v.comment_id WHERE c.room_id = $1 GROUP BY c.id")
Flux<Comment> findByRoomIdWithScore(UUID roomId);
Flux<Comment> findByRoomId(UUID roomId);
#Transactional
Flux<Void> deleteByRoomId(UUID roomId);
}
and my Comment Object is this:
#Table
public class Comment implements Persistable<UUID> {
#Id
private UUID id;
private UUID roomId;
private UUID creatorId;
private String body;
private Timestamp timestamp;
private boolean read;
private boolean favorite;
private int correct;
private boolean ack;
#Transient
private int score;
private String tag;
private String answer;
#Override
public boolean isNew() {
return id == null;
}
public UUID getId() {
return id;
}
public void setId(UUID id) {
this.id = id;
}
public UUID getRoomId() {
return roomId;
}
public void setRoomId(UUID roomId) {
this.roomId = roomId;
}
public UUID getCreatorId() {
return creatorId;
}
public void setCreatorId(UUID creatorId) {
this.creatorId = creatorId;
}
public String getBody() {
return body;
}
public void setBody(String body) {
this.body = body;
}
public Timestamp getTimestamp() {
return timestamp;
}
public void setTimestamp(Timestamp timestamp) {
this.timestamp = timestamp;
}
public boolean isRead() {
return read;
}
public void setRead(boolean read) {
this.read = read;
}
public boolean isFavorite() {
return favorite;
}
public void setFavorite(boolean favorite) {
this.favorite = favorite;
}
public int getCorrect() {
return correct;
}
public void setCorrect(int correct) {
this.correct = correct;
}
public boolean isAck() {
return ack;
}
public void setAck(boolean ack) {
this.ack = ack;
}
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
public String getTag() {
return tag;
}
public void setTag(String tag) {
this.tag = tag;
}
public String getAnswer() {
return answer;
}
public void setAnswer(String answer) {
this.answer = answer;
}
#Override
public String toString() {
return "Comment{" +
"id='" + id + '\'' +
", roomId='" + roomId + '\'' +
", creatorId='" + creatorId + '\'' +
", body='" + body + '\'' +
", timestamp=" + timestamp +
", read=" + read +
", favorite=" + favorite +
", correct=" + correct +
", ack=" + ack +
", score=" + score +
", tag=" + tag +
", answer=" + answer +
'}';
}
}
I´ve already tried to make another Comment class without the transient annotation, but that doesn´t work because of the used Repository i guess: reactor.core.Exceptions$ErrorCallbackNotImplemented: java.lang.IllegalArgumentException: Property must not be null!

Answer 1

The solution was to create another Class which extends Comment with the non transient score attribute. This could be casted back into a comment and the score is set