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in Technique[技术] by (71.8m points)

Join fetch property of embeddable in hibernate

These are my mapped classes:

@Entity
public class Item {
...
     @ElementCollection
     @CollectionTable(name = "BID")
     private Set<Bid> bids = new HashSet<>();
...
}

@Embeddable
@Immutable
public class Bid implements Serializable {
...
    @ManyToOne(fetch = FetchType.LAZY)
    private User bidder;
...
}

@Entity
public class User {
...
}

Is there a way to query all bids and join fetch all bidders to avoid n+1 problem?

It will be smth like this

session.createQuery("SELECT b FROM Item i " +
                "JOIN i.bids b " +
                "JOIN FETCH b.bidder", Bid.class)

but this fails with: org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list[FromElement{explicit,not a collection join,fetch join,fetch non-lazy properties,classAlias=null,role=null.bidder...]

I know that making Bid class entity instead of embeddable will solve the problem, but i am interested is there any way how to do this with this mapping


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1 Answer

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by (71.8m points)

I think this is a bug in older Hibernate versions. Try updating to the latest 5.4 version.


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