因此，我尝试在spring数据中进行投影查询。这是我的模型（为了避免大量发布类，我将省略构造函数和一些注解）：

public class TutorialDAO implements Serializable {
    private UUID id;
    private LocalDateTime created;
    private String createdBy;
    private LocalDateTime lastModified;
    private String lastModifiedBy;
    private int version;
    private boolean exclusive;

    @ManyToMany(mappedBy = "tutorials", cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
    private Set<TopicDAO> topics = new HashSet<>();

    @ElementCollection(fetch = FetchType.EAGER)
    private Set<SectionDAO> sections = new HashSet<>();

    @ManyToMany(cascade = CascadeType.PERSIST, fetch = FetchType.LAZY)
    @JoinTable(name = "tutorial_courses", joinColumns = @JoinColumn(name = "tutorial_id"), inverseJoinColumns = @JoinColumn(name = "course_id"))
    private Set<CourseDAO> courses = new HashSet<>();

    @OneToMany(mappedBy = "tutorial", cascade = { CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST,
            CascadeType.REFRESH }, orphanRemoval = true, fetch = FetchType.EAGER)
    @MapKey(name = "localizedId.locale")
    private Map<String, LocalizableTutorial> localizations = new HashMap<>();

public class TopicDAO implements Serializable {
    private UUID id;
    private String topic;

    @ManyToMany(cascade = CascadeType.PERSIST, fetch = FetchType.LAZY)
    private Set<TutorialDAO> tutorials = new HashSet<>();
}

public class LocalizedTutorialDAO {
    private UUID id;
    private LocalDateTime created;
    private String createdBy;
    private LocalDateTime lastModified;
    private String lastModifiedBy;
    private int version;
    private boolean exclusive;
    private String name, description;
    private Set<TopicDAO> topics = new HashSet<>();
    private Set<SectionDAO> sections = new HashSet<>();

    public LocalizedTutorialDAO(UUID id, LocalDateTime created, String createdBy, LocalDateTime lastModified,
            String lastModifiedBy, int version, boolean exclusive, String name, String description,
            Set<TopicDAO> topics) {
        super(id, created, createdBy, lastModified, lastModifiedBy, version);
        System.out.println(topics);
        System.out.println();
        this.name = name;
        this.description = description;
        this.topics = topics;
    }
}

我试图做一个投影查询，它“填充”localizedtutorialdao类，这意味着我想要主题关系，例如（章节也会发生同样的情况，但因为它是一个类似的问题，所以我只会提到主题）。我有这个@query注解：

select new LocalizedTutorialDAO(t.id, t.created, t.createdBy, t.lastModified, t.lastModifiedBy, t.version, t.exclusive, (VALUE(l)).name, (VALUE(l)).description, topics) from tutorial t join t.localizations l join t.topics as topics where (VALUE(l)).name like %:name% and (KEY(l)) = :lang

要澄清的是，tutorialdao对象具有多语言支持，我的查询获取tutorialdao中的“normal”变量以及主题和部分关系。然后它从给定的语言中获取名称和描述，例如，我想看一个用葡萄牙语命名为“烹饪鱼”的教程-“pt”。现在，关于名称和描述的这一部分正在运行，我在没有获得主题和部分的情况下对其进行了测试，实体得到了正确填充。我这里的问题是我尝试了原生sql和spring数据非原生查询，但我永远无法让它工作。像这样，当前的查询，它说：

org.hibernate.hql.internal.ast.QuerySyntaxException: Unable to locate appropriate constructor on class [com.fullstack.daos.projections.LocalizedTutorialDAO]. Expected arguments are: java.util.UUID, java.time.LocalDateTime, java.lang.String, java.time.LocalDateTime, java.lang.String, int, boolean, java.lang.String, java.lang.String, com.fullstack.daos.TopicDAO [select new com.fullstack.daos.projections.LocalizedTutorialDAO(t.id, t.created, t.createdBy, t.lastModified, t.lastModifiedBy, t.version, t.exclusive, (VALUE(l)).name, (VALUE(l)).description, topics) from com.fullstack.daos.TutorialDAO t join t.localizations l join t.topics as topics where (VALUE(l)).name like :name and (KEY(l)) = :lang]

如果我尝试本机，而不是把topic放在构造函数中，我会把topic.id，topic.topic放在构造函数中，它永远不会工作，因为它说它不能将topicdao转换为set。有没有办法告诉hibernate怎么做？例如，spring works自动生成的findbyid（）查询生成以下sql查询：

select
        tutorialda0_.id as id1_33_0_,
        tutorialda0_.created as created2_33_0_,
        tutorialda0_.created_by as created_3_33_0_,
        tutorialda0_.last_modified as last_mod4_33_0_,
        tutorialda0_.last_modified_by as last_mod5_33_0_,
        tutorialda0_.version as version6_33_0_,
        tutorialda0_.exclusive as exclusiv7_33_0_,
        localizati1_.id as id1_8_1_,
        localizati1_.locale as locale2_8_1_,
        localizati1_.locale as formula413_1_,
        localizati1_.id as id1_8_2_,
        localizati1_.locale as locale2_8_2_,
        localizati1_.description as descript3_8_2_,
        localizati1_.name as name4_8_2_,
        sections2_.tutorial_id as tutorial1_34_3_,
        sectiondao3_.id as sections2_34_3_,
        sectiondao3_.id as id1_22_4_,
        sectiondao3_.parent_id as parent_i2_22_4_,
        children4_.parent_id as parent_i2_22_5_,
        children4_.id as id1_22_5_,
        children4_.id as id1_22_6_,
        children4_.parent_id as parent_i2_22_6_,
        topics5_.tutorials_id as tutorial2_31_7_,
        topicdao6_.id as topics_i1_31_7_,
        topicdao6_.id as id1_27_8_,
        topicdao6_.topic as topic2_27_8_
    from
        tutorials tutorialda0_
    left outer join
        localized_tutorial localizati1_
            on tutorialda0_.id=localizati1_.id
    left outer join
        tutorials_sections sections2_
            on tutorialda0_.id=sections2_.tutorial_id
    left outer join
        sections sectiondao3_
            on sections2_.sections_id=sectiondao3_.id
    left outer join
        sections children4_
            on sectiondao3_.id=children4_.parent_id
    left outer join
        topics_tutorials topics5_
            on tutorialda0_.id=topics5_.tutorials_id
    left outer join
        topics topicdao6_
            on topics5_.topics_id=topicdao6_.id
    where
        tutorialda0_.id=?