投影的休眠標准

Question

我有兩個與@OneToOne關系的類： User和Player 。

用戶包含一個播放器：

@Entity
@Table(name = "user")
public class User {
    @Column(name = "nickname")
    private String nickname;

    @OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "id_player")
    private Player player;

   //getters and setters...
}

我想只使用nickname和player查詢用戶，而對於player我並不需要所有屬性，我只想要2。

這就是我現在所擁有的：

    //Projections for the class User
    ProjectionList projectionList = Projections.projectionList();
    projectionList.add(Projections.property("id"), "id");
    projectionList.add(Projections.property("nickname"), "nickname");
    projectionList.add(Projections.property("player"), "player");

    Criteria criteria = session.createCriteria(User.class);
    criteria.setFirstResult(player.getPvpRank() - 5);
    criteria.setMaxResults(11);
    criteria.createAlias("player", "p");
    criteria.addOrder(Order.asc("p.pvpRank"));
    criteria.setProjection(projectionList);
    criteria.setResultTransformer(Transformers.aliasToBean(User.class));

我僅獲得nickname ， id和player ，但是如何設置對玩家的投射，只獲得player.level而不是所有屬性？

Answer 1

它認為這完全符合您的建議：

projectionList.add(Projections.property("player.level"), "player.level");

Answer 2

首先在User為JoinColumn表Player 創建別名 ， 然后在您的projectionList中引用它 。

Criteria criteria = session.createCriteria(User.class);
criteria.createAlias("player", "p");
projectionList.add(Projections.property("p.level"), "player");
...
criteria.setProjection(projectionList);
criteria.setResultTransformer(Transformers.aliasToBean(User.class));

我希望這可以幫助你。