我有一个简单的Field实体，必须使用连接加载子Selector实体。

@Entity
public class Field implements Serializable {
    @Id
    private Long id;

    @NotNull
    private Long userId;

    private String selectorId;

    // ......

    @JoinColumns({
            @JoinColumn(name = "userId", referencedColumnName = "userId", insertable = false, updatable = false),
            @JoinColumn(name = "selectorId", referencedColumnName = "selectorId", insertable = false, updatable = false)
    })
    @ManyToOne
    @Fetch(FetchMode.JOIN)
    private Selector selector;
}

Hibernate会执行此操作并生成下面的sql。看起来不错：

SELECT field0_.id AS id1_25_0_,
       -- ... i've cut redundant lines ...
       selector1_.id AS id1_54_1_,
       selector1_.selector_id AS selector4_54_1_,
       selector1_.user_id AS user_i5_54_1_,
       selector1_.url AS url6_54_1_
FROM field field0_
         LEFT OUTER JOIN selector selector1_
                         ON field0_.user_id = selector1_.user_id AND field0_.selector_id = selector1_.selector_id
WHERE field0_.id=?;

但是Hibernate在执行完上面的查询后，立即为每个Field生成并执行第二个sql，重新选择Selector实体，如何防止执行第二个sql？第一个查询中应该已经加载了Selector，并带有join。

SELECT selector0_.id AS id1_54_0_,
       selector0_.selector_id AS selector4_54_0_,
       selector0_.user_id AS user_i5_54_0_,
       selector0_.url AS url6_54_0_
FROM selector selector0_
WHERE selector0_.user_id=?
  AND selector0_.selector_id=?;