关联对象的 Hibernate 标准

Question

我有 DTO 对象的下一个结构：

public class MainDTO implements Serializable {
    private Long mainId;
    private String name;
    ... //some other fields
    private boolean disabled;

    @ManyToOne()
    @JoinColumn(name = "root_id")
    private RootDTO root;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "child_id", updatable = false, referencedColumnName = "child_id")
    @Cascade(value = { CascadeType.ALL, CascadeType.DELETE_ORPHAN })
    private ChildDTO child;

    ...
}

public class RootDTO implements Serializable {
    ... //some other fields
    private boolean disabled;

    ...
}


public class ChildDTO implements Serializable {
    private Long childId;
    ... //some other fields
    private boolean disabled;

    @ManyToOne()
    @JoinColumn(name = "info_id")
    private InfoDTO info;

    ...
}

public class InfoDTO implements Serializable {
    private Long infoId;
    ... //some other fields
    private boolean disabled;

    ...
}

我需要填充 Map> (>)，具有以下限制：

MainDTO.disabled = false、

MainDTO.root != null、

MainDTO.root.disabled = false、

MainDTO.child.disabled = false,

MainDTO.child.info != null,

MainDTO.child.info.disabled = false

这是我编写的代码，但卡在了来自 InfoDTO 的 select infoId 中：

Criteria rootCriteria = getSession().createCriteria(
        MainDTO.class);

// check that root is enabled
rootCriteria.createCriteria("root", "root").add(
    Restrictions.eq("disabled", false));

// check that child is enabled
Criteria childCriteria = rootCriteria
    .createCriteria("child", "child")
    .add(Restrictions.eq("disabled", false))
    .add(Restrictions.isNotNull("info"));

// check that info is enabled
childCriteria
    .createCriteria("info", "info")
    .add(Restrictions.eq("disabled", false));

ProjectionList rootProjection = Projections.projectionList()
    .add(Projections.property("mainId"))
    .add(Projections.property("name"))
    .add(Projections.property("child.info")); //HOW TO SELECT ONLY ID??
rootCriteria.setProjection(rootProjection);
rootCriteria.add(Restrictions.eq("disabled", false))
    .add(Restrictions.isNotNull("root"))
    .add(Restrictions.isNotNull("child"));

非常感谢！

Answer 1

首先，调用实体DTO确实令人困惑。

现在关于您的问题，您应该使用您在投影中定义的别名

ProjectionList rootProjection = 
    Projections.projectionList()
               .add(Projections.property("mainId"))
               .add(Projections.property("name"))
               .add(Projections.property("info.infoId"));

此外，考虑到您正在对 root 和 child 进行内部联接，最后两个限制是不必要的：内部联接已经确保它们不为空。