投影的休眠标准

Question

我有 2 个具有 @OneToOne 关系的类：User 和 Player。

用户包含一个玩家：

@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...
}

我只想用nickname 和player 查询用户，用player 我不想要所有属性，我只想要2 个。

这就是我现在拥有的：

    //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));

我只得到nickname、id 和player，但我怎样才能将投影设置到玩家只得到player.level 而不是所有属性？

Answer 1

首先为 User 中的 JoinColumn 表 Player 创建别名 &然后在你的 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));

希望对你有帮助。

Answer 2

它认为它完全按照你的建议：

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